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* [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices
@ 2020-03-19 20:16 Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
                   ` (6 more replies)
  0 siblings, 7 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

Hi,

This patch set adds:
* New IOCTL VFIO_IOMMU_DIRTY_PAGES to get dirty pages bitmap with
  respect to IOMMU container rather than per device. All pages pinned by
  vendor driver through vfio_pin_pages external API has to be marked as
  dirty during  migration. When IOMMU capable device is present in the
  container and all pages are pinned and mapped, then all pages are marked
  dirty.
  When there are CPU writes, CPU dirty page tracking can identify dirtied
  pages, but any page pinned by vendor driver can also be written by
  device. As of now there is no device which has hardware support for
  dirty page tracking. So all pages which are pinned should be considered
  as dirty.
  This ioctl is also used to start/stop dirty pages tracking for pinned and
  unpinned pages while migration is active.

* Updated IOCTL VFIO_IOMMU_UNMAP_DMA to get dirty pages bitmap before
  unmapping IO virtual address range.
  With vIOMMU, during pre-copy phase of migration, while CPUs are still
  running, IO virtual address unmap can happen while device still keeping
  reference of guest pfns. Those pages should be reported as dirty before
  unmap, so that VFIO user space application can copy content of those
  pages from source to destination.

* Patch 7 detect if IOMMU capable device driver is smart to report pages
  to be marked dirty by pinning pages using vfio_pin_pages() API.


Yet TODO:
Since there is no device which has hardware support for system memmory
dirty bitmap tracking, right now there is no other API from vendor driver
to VFIO IOMMU module to report dirty pages. In future, when such hardware
support will be implemented, an API will be required such that vendor
driver could report dirty pages to VFIO module during migration phases.

Adding revision history from previous QEMU patch set to understand KABI
changes done till now

v14 -> v15
- Minor edits and nit picks.
- In the verification of user allocated bitmap memory, added check of
   maximum size.
- Patches are on tag: next-20200318 and 1-3 patches from Yan's series
  https://lkml.org/lkml/2020/3/12/1255

v13 -> v14
- Added struct vfio_bitmap to kabi. updated structure
  vfio_iommu_type1_dirty_bitmap_get and vfio_iommu_type1_dma_unmap.
- All small changes suggested by Alex.
- Patches are on tag: next-20200318 and 1-3 patches from Yan's series
  https://lkml.org/lkml/2020/3/12/1255

v12 -> v13
- Changed bitmap allocation in vfio_iommu_type1 to per vfio_dma
- Changed VFIO_IOMMU_DIRTY_PAGES ioctl behaviour to be per vfio_dma range.
- Changed vfio_iommu_type1_dirty_bitmap structure to have separate data
  field.

v11 -> v12
- Changed bitmap allocation in vfio_iommu_type1.
- Remove atomicity of ref_count.
- Updated comments for migration device state structure about error
  reporting.
- Nit picks from v11 reviews

v10 -> v11
- Fix pin pages API to free vpfn if it is marked as unpinned tracking page.
- Added proposal to detect if IOMMU capable device calls external pin pages
  API to mark pages dirty.
- Nit picks from v10 reviews

v9 -> v10:
- Updated existing VFIO_IOMMU_UNMAP_DMA ioctl to get dirty pages bitmap
  during unmap while migration is active
- Added flag in VFIO_IOMMU_GET_INFO to indicate driver support dirty page
  tracking.
- If iommu_mapped, mark all pages dirty.
- Added unpinned pages tracking while migration is active.
- Updated comments for migration device state structure with bit
  combination table and state transition details.

v8 -> v9:
- Split patch set in 2 sets, Kernel and QEMU.
- Dirty pages bitmap is queried from IOMMU container rather than from
  vendor driver for per device. Added 2 ioctls to achieve this.

v7 -> v8:
- Updated comments for KABI
- Added BAR address validation check during PCI device's config space load
  as suggested by Dr. David Alan Gilbert.
- Changed vfio_migration_set_state() to set or clear device state flags.
- Some nit fixes.

v6 -> v7:
- Fix build failures.

v5 -> v6:
- Fix build failure.

v4 -> v5:
- Added decriptive comment about the sequence of access of members of
  structure vfio_device_migration_info to be followed based on Alex's
  suggestion
- Updated get dirty pages sequence.
- As per Cornelia Huck's suggestion, added callbacks to VFIODeviceOps to
  get_object, save_config and load_config.
- Fixed multiple nit picks.
- Tested live migration with multiple vfio device assigned to a VM.

v3 -> v4:
- Added one more bit for _RESUMING flag to be set explicitly.
- data_offset field is read-only for user space application.
- data_size is read for every iteration before reading data from migration,
  that is removed assumption that data will be till end of migration
  region.
- If vendor driver supports mappable sparsed region, map those region
  during setup state of save/load, similarly unmap those from cleanup
  routines.
- Handles race condition that causes data corruption in migration region
  during save device state by adding mutex and serialiaing save_buffer and
  get_dirty_pages routines.
- Skip called get_dirty_pages routine for mapped MMIO region of device.
- Added trace events.
- Split into multiple functional patches.

v2 -> v3:
- Removed enum of VFIO device states. Defined VFIO device state with 2
  bits.
- Re-structured vfio_device_migration_info to keep it minimal and defined
  action on read and write access on its members.

v1 -> v2:
- Defined MIGRATION region type and sub-type which should be used with
  region type capability.
- Re-structured vfio_device_migration_info. This structure will be placed
  at 0th offset of migration region.
- Replaced ioctl with read/write for trapped part of migration region.
- Added both type of access support, trapped or mmapped, for data section
  of the region.
- Moved PCI device functions to pci file.
- Added iteration to get dirty page bitmap until bitmap for all requested
  pages are copied.

Thanks,
Kirti



Kirti Wankhede (7):
  vfio: KABI for migration interface for device state
  vfio iommu: Remove atomicity of ref_count of pinned pages
  vfio iommu: Add ioctl definition for dirty pages tracking.
  vfio iommu: Implementation of ioctl for dirty pages tracking.
  vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap
  vfio iommu: Adds flag to indicate dirty pages tracking capability
    support
  vfio: Selective dirty page tracking if IOMMU backed device pins pages

 drivers/vfio/vfio.c             |  13 +-
 drivers/vfio/vfio_iommu_type1.c | 398 ++++++++++++++++++++++++++++++++++++++--
 include/linux/vfio.h            |   4 +-
 include/uapi/linux/vfio.h       | 297 +++++++++++++++++++++++++++++-
 4 files changed, 690 insertions(+), 22 deletions(-)

-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  2020-03-23 20:30   ` Auger Eric
  2020-03-26  9:33   ` Christoph Hellwig
  2020-03-19 20:16 ` [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Kirti Wankhede
                   ` (5 subsequent siblings)
  6 siblings, 2 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

- Defined MIGRATION region type and sub-type.

- Defined vfio_device_migration_info structure which will be placed at the
  0th offset of migration region to get/set VFIO device related
  information. Defined members of structure and usage on read/write access.

- Defined device states and state transition details.

- Defined sequence to be followed while saving and resuming VFIO device.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 include/uapi/linux/vfio.h | 227 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 227 insertions(+)

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 9e843a147ead..d0021467af53 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -305,6 +305,7 @@ struct vfio_region_info_cap_type {
 #define VFIO_REGION_TYPE_PCI_VENDOR_MASK	(0xffff)
 #define VFIO_REGION_TYPE_GFX                    (1)
 #define VFIO_REGION_TYPE_CCW			(2)
+#define VFIO_REGION_TYPE_MIGRATION              (3)
 
 /* sub-types for VFIO_REGION_TYPE_PCI_* */
 
@@ -379,6 +380,232 @@ struct vfio_region_gfx_edid {
 /* sub-types for VFIO_REGION_TYPE_CCW */
 #define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD	(1)
 
+/* sub-types for VFIO_REGION_TYPE_MIGRATION */
+#define VFIO_REGION_SUBTYPE_MIGRATION           (1)
+
+/*
+ * The structure vfio_device_migration_info is placed at the 0th offset of
+ * the VFIO_REGION_SUBTYPE_MIGRATION region to get and set VFIO device related
+ * migration information. Field accesses from this structure are only supported
+ * at their native width and alignment. Otherwise, the result is undefined and
+ * vendor drivers should return an error.
+ *
+ * device_state: (read/write)
+ *      - The user application writes to this field to inform the vendor driver
+ *        about the device state to be transitioned to.
+ *      - The vendor driver should take the necessary actions to change the
+ *        device state. After successful transition to a given state, the
+ *        vendor driver should return success on write(device_state, state)
+ *        system call. If the device state transition fails, the vendor driver
+ *        should return an appropriate -errno for the fault condition.
+ *      - On the user application side, if the device state transition fails,
+ *	  that is, if write(device_state, state) returns an error, read
+ *	  device_state again to determine the current state of the device from
+ *	  the vendor driver.
+ *      - The vendor driver should return previous state of the device unless
+ *        the vendor driver has encountered an internal error, in which case
+ *        the vendor driver may report the device_state VFIO_DEVICE_STATE_ERROR.
+ *      - The user application must use the device reset ioctl to recover the
+ *        device from VFIO_DEVICE_STATE_ERROR state. If the device is
+ *        indicated to be in a valid device state by reading device_state, the
+ *        user application may attempt to transition the device to any valid
+ *        state reachable from the current state or terminate itself.
+ *
+ *      device_state consists of 3 bits:
+ *      - If bit 0 is set, it indicates the _RUNNING state. If bit 0 is clear,
+ *        it indicates the _STOP state. When the device state is changed to
+ *        _STOP, driver should stop the device before write() returns.
+ *      - If bit 1 is set, it indicates the _SAVING state, which means that the
+ *        driver should start gathering device state information that will be
+ *        provided to the VFIO user application to save the device's state.
+ *      - If bit 2 is set, it indicates the _RESUMING state, which means that
+ *        the driver should prepare to resume the device. Data provided through
+ *        the migration region should be used to resume the device.
+ *      Bits 3 - 31 are reserved for future use. To preserve them, the user
+ *      application should perform a read-modify-write operation on this
+ *      field when modifying the specified bits.
+ *
+ *  +------- _RESUMING
+ *  |+------ _SAVING
+ *  ||+----- _RUNNING
+ *  |||
+ *  000b => Device Stopped, not saving or resuming
+ *  001b => Device running, which is the default state
+ *  010b => Stop the device & save the device state, stop-and-copy state
+ *  011b => Device running and save the device state, pre-copy state
+ *  100b => Device stopped and the device state is resuming
+ *  101b => Invalid state
+ *  110b => Error state
+ *  111b => Invalid state
+ *
+ * State transitions:
+ *
+ *              _RESUMING  _RUNNING    Pre-copy    Stop-and-copy   _STOP
+ *                (100b)     (001b)     (011b)        (010b)       (000b)
+ * 0. Running or default state
+ *                             |
+ *
+ * 1. Normal Shutdown (optional)
+ *                             |------------------------------------->|
+ *
+ * 2. Save the state or suspend
+ *                             |------------------------->|---------->|
+ *
+ * 3. Save the state during live migration
+ *                             |----------->|------------>|---------->|
+ *
+ * 4. Resuming
+ *                  |<---------|
+ *
+ * 5. Resumed
+ *                  |--------->|
+ *
+ * 0. Default state of VFIO device is _RUNNNG when the user application starts.
+ * 1. During normal shutdown of the user application, the user application may
+ *    optionally change the VFIO device state from _RUNNING to _STOP. This
+ *    transition is optional. The vendor driver must support this transition but
+ *    must not require it.
+ * 2. When the user application saves state or suspends the application, the
+ *    device state transitions from _RUNNING to stop-and-copy and then to _STOP.
+ *    On state transition from _RUNNING to stop-and-copy, driver must stop the
+ *    device, save the device state and send it to the application through the
+ *    migration region. The sequence to be followed for such transition is given
+ *    below.
+ * 3. In live migration of user application, the state transitions from _RUNNING
+ *    to pre-copy, to stop-and-copy, and to _STOP.
+ *    On state transition from _RUNNING to pre-copy, the driver should start
+ *    gathering the device state while the application is still running and send
+ *    the device state data to application through the migration region.
+ *    On state transition from pre-copy to stop-and-copy, the driver must stop
+ *    the device, save the device state and send it to the user application
+ *    through the migration region.
+ *    Vendor drivers must support the pre-copy state even for implementations
+ *    where no data is provided to the user before the stop-and-copy state. The
+ *    user must not be required to consume all migration data before the device
+ *    transitions to a new state, including the stop-and-copy state.
+ *    The sequence to be followed for above two transitions is given below.
+ * 4. To start the resuming phase, the device state should be transitioned from
+ *    the _RUNNING to the _RESUMING state.
+ *    In the _RESUMING state, the driver should use the device state data
+ *    received through the migration region to resume the device.
+ * 5. After providing saved device data to the driver, the application should
+ *    change the state from _RESUMING to _RUNNING.
+ *
+ * reserved:
+ *      Reads on this field return zero and writes are ignored.
+ *
+ * pending_bytes: (read only)
+ *      The number of pending bytes still to be migrated from the vendor driver.
+ *
+ * data_offset: (read only)
+ *      The user application should read data_offset in the migration region
+ *      from where the user application should read the device data during the
+ *      _SAVING state or write the device data during the _RESUMING state. See
+ *      below for details of sequence to be followed.
+ *
+ * data_size: (read/write)
+ *      The user application should read data_size to get the size in bytes of
+ *      the data copied in the migration region during the _SAVING state and
+ *      write the size in bytes of the data copied in the migration region
+ *      during the _RESUMING state.
+ *
+ * The format of the migration region is as follows:
+ *  ------------------------------------------------------------------
+ * |vfio_device_migration_info|    data section                      |
+ * |                          |     ///////////////////////////////  |
+ * ------------------------------------------------------------------
+ *   ^                              ^
+ *  offset 0-trapped part        data_offset
+ *
+ * The structure vfio_device_migration_info is always followed by the data
+ * section in the region, so data_offset will always be nonzero. The offset
+ * from where the data is copied is decided by the kernel driver. The data
+ * section can be trapped, mapped, or partitioned, depending on how the kernel
+ * driver defines the data section. The data section partition can be defined
+ * as mapped by the sparse mmap capability. If mmapped, data_offset should be
+ * page aligned, whereas initial section which contains the
+ * vfio_device_migration_info structure, might not end at the offset, which is
+ * page aligned. The user is not required to access through mmap regardless
+ * of the capabilities of the region mmap.
+ * The vendor driver should determine whether and how to partition the data
+ * section. The vendor driver should return data_offset accordingly.
+ *
+ * The sequence to be followed for the _SAVING|_RUNNING device state or
+ * pre-copy phase and for the _SAVING device state or stop-and-copy phase is as
+ * follows:
+ * a. Read pending_bytes, indicating the start of a new iteration to get device
+ *    data. Repeated read on pending_bytes at this stage should have no side
+ *    effects.
+ *    If pending_bytes == 0, the user application should not iterate to get data
+ *    for that device.
+ *    If pending_bytes > 0, perform the following steps.
+ * b. Read data_offset, indicating that the vendor driver should make data
+ *    available through the data section. The vendor driver should return this
+ *    read operation only after data is available from (region + data_offset)
+ *    to (region + data_offset + data_size).
+ * c. Read data_size, which is the amount of data in bytes available through
+ *    the migration region.
+ *    Read on data_offset and data_size should return the offset and size of
+ *    the current buffer if the user application reads data_offset and
+ *    data_size more than once here.
+ * d. Read data_size bytes of data from (region + data_offset) from the
+ *    migration region.
+ * e. Process the data.
+ * f. Read pending_bytes, which indicates that the data from the previous
+ *    iteration has been read. If pending_bytes > 0, go to step b.
+ *
+ * If an error occurs during the above sequence, the vendor driver can return
+ * an error code for next read() or write() operation, which will terminate the
+ * loop. The user application should then take the next necessary action, for
+ * example, failing migration or terminating the user application.
+ *
+ * The user application can transition from the _SAVING|_RUNNING
+ * (pre-copy state) to the _SAVING (stop-and-copy) state regardless of the
+ * number of pending bytes. The user application should iterate in _SAVING
+ * (stop-and-copy) until pending_bytes is 0.
+ *
+ * The sequence to be followed while _RESUMING device state is as follows:
+ * While data for this device is available, repeat the following steps:
+ * a. Read data_offset from where the user application should write data.
+ * b. Write migration data starting at the migration region + data_offset for
+ *    the length determined by data_size from the migration source.
+ * c. Write data_size, which indicates to the vendor driver that data is
+ *    written in the migration region. Vendor driver should apply the
+ *    user-provided migration region data to the device resume state.
+ *
+ * For the user application, data is opaque. The user application should write
+ * data in the same order as the data is received and the data should be of
+ * same transaction size at the source.
+ */
+
+struct vfio_device_migration_info {
+	__u32 device_state;         /* VFIO device state */
+#define VFIO_DEVICE_STATE_STOP      (0)
+#define VFIO_DEVICE_STATE_RUNNING   (1 << 0)
+#define VFIO_DEVICE_STATE_SAVING    (1 << 1)
+#define VFIO_DEVICE_STATE_RESUMING  (1 << 2)
+#define VFIO_DEVICE_STATE_MASK      (VFIO_DEVICE_STATE_RUNNING | \
+				     VFIO_DEVICE_STATE_SAVING |  \
+				     VFIO_DEVICE_STATE_RESUMING)
+
+#define VFIO_DEVICE_STATE_VALID(state) \
+	(state & VFIO_DEVICE_STATE_RESUMING ? \
+	(state & VFIO_DEVICE_STATE_MASK) == VFIO_DEVICE_STATE_RESUMING : 1)
+
+#define VFIO_DEVICE_STATE_IS_ERROR(state) \
+	((state & VFIO_DEVICE_STATE_MASK) == (VFIO_DEVICE_STATE_SAVING | \
+					      VFIO_DEVICE_STATE_RESUMING))
+
+#define VFIO_DEVICE_STATE_SET_ERROR(state) \
+	((state & ~VFIO_DEVICE_STATE_MASK) | VFIO_DEVICE_SATE_SAVING | \
+					     VFIO_DEVICE_STATE_RESUMING)
+
+	__u32 reserved;
+	__u64 pending_bytes;
+	__u64 data_offset;
+	__u64 data_size;
+} __attribute__((packed));
+
 /*
  * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
  * which allows direct access to non-MSIX registers which happened to be within
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  2020-03-23 20:30   ` Auger Eric
  2020-03-19 20:16 ` [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
                   ` (4 subsequent siblings)
  6 siblings, 1 reply; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

vfio_pfn.ref_count is always updated by holding iommu->lock, using atomic
variable is overkill.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 9fdfae1cb17a..70aeab921d0f 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -112,7 +112,7 @@ struct vfio_pfn {
 	struct rb_node		node;
 	dma_addr_t		iova;		/* Device address */
 	unsigned long		pfn;		/* Host pfn */
-	atomic_t		ref_count;
+	unsigned int		ref_count;
 };
 
 struct vfio_regions {
@@ -233,7 +233,7 @@ static int vfio_add_to_pfn_list(struct vfio_dma *dma, dma_addr_t iova,
 
 	vpfn->iova = iova;
 	vpfn->pfn = pfn;
-	atomic_set(&vpfn->ref_count, 1);
+	vpfn->ref_count = 1;
 	vfio_link_pfn(dma, vpfn);
 	return 0;
 }
@@ -251,7 +251,7 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
 	struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
 
 	if (vpfn)
-		atomic_inc(&vpfn->ref_count);
+		vpfn->ref_count++;
 	return vpfn;
 }
 
@@ -259,7 +259,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
 {
 	int ret = 0;
 
-	if (atomic_dec_and_test(&vpfn->ref_count)) {
+	vpfn->ref_count--;
+	if (!vpfn->ref_count) {
 		ret = put_pfn(vpfn->pfn, dma->prot);
 		vfio_remove_from_pfn_list(dma, vpfn);
 	}
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking.
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  2020-03-23 21:11   ` Auger Eric
  2020-03-19 20:16 ` [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
                   ` (3 subsequent siblings)
  6 siblings, 1 reply; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

IOMMU container maintains a list of all pages pinned by vfio_pin_pages API.
All pages pinned by vendor driver through this API should be considered as
dirty during migration. When container consists of IOMMU capable device and
all pages are pinned and mapped, then all pages are marked dirty.
Added support to start/stop dirtied pages tracking and to get bitmap of all
dirtied pages for requested IO virtual address range.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 include/uapi/linux/vfio.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index d0021467af53..8138f94cac15 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -995,6 +995,12 @@ struct vfio_iommu_type1_dma_map {
 
 #define VFIO_IOMMU_MAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 13)
 
+struct vfio_bitmap {
+	__u64        pgsize;	/* page size for bitmap */
+	__u64        size;	/* in bytes */
+	__u64 __user *data;	/* one bit per page */
+};
+
 /**
  * VFIO_IOMMU_UNMAP_DMA - _IOWR(VFIO_TYPE, VFIO_BASE + 14,
  *							struct vfio_dma_unmap)
@@ -1021,6 +1027,55 @@ struct vfio_iommu_type1_dma_unmap {
 #define VFIO_IOMMU_ENABLE	_IO(VFIO_TYPE, VFIO_BASE + 15)
 #define VFIO_IOMMU_DISABLE	_IO(VFIO_TYPE, VFIO_BASE + 16)
 
+/**
+ * VFIO_IOMMU_DIRTY_PAGES - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
+ *                                     struct vfio_iommu_type1_dirty_bitmap)
+ * IOCTL is used for dirty pages tracking. Caller sets argsz, which is size of
+ * struct vfio_iommu_type1_dirty_bitmap. Caller set flag depend on which
+ * operation to perform, details as below:
+ *
+ * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_START set, indicates
+ * migration is active and IOMMU module should track pages which are dirtied or
+ * potentially dirtied by device.
+ * Dirty pages are tracked until tracking is stopped by user application by
+ * setting VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP flag.
+ *
+ * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP set, indicates
+ * IOMMU should stop tracking dirtied pages.
+ *
+ * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP flag set,
+ * IOCTL returns dirty pages bitmap for IOMMU container during migration for
+ * given IOVA range. User must provide data[] as the structure
+ * vfio_iommu_type1_dirty_bitmap_get through which user provides IOVA range and
+ * pgsize. This interface supports to get bitmap of smallest supported pgsize
+ * only and can be modified in future to get bitmap of specified pgsize.
+ * User must allocate memory for bitmap, zero the bitmap memory and set size
+ * of allocated memory in bitmap_size field. One bit is used to represent one
+ * page consecutively starting from iova offset. User should provide page size
+ * in 'pgsize'. Bit set in bitmap indicates page at that offset from iova is
+ * dirty. Caller must set argsz including size of structure
+ * vfio_iommu_type1_dirty_bitmap_get.
+ *
+ * Only one of the flags _START, STOP and _GET may be specified at a time.
+ *
+ */
+struct vfio_iommu_type1_dirty_bitmap {
+	__u32        argsz;
+	__u32        flags;
+#define VFIO_IOMMU_DIRTY_PAGES_FLAG_START	(1 << 0)
+#define VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP	(1 << 1)
+#define VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP	(1 << 2)
+	__u8         data[];
+};
+
+struct vfio_iommu_type1_dirty_bitmap_get {
+	__u64              iova;	/* IO virtual address */
+	__u64              size;	/* Size of iova range */
+	struct vfio_bitmap bitmap;
+};
+
+#define VFIO_IOMMU_DIRTY_PAGES             _IO(VFIO_TYPE, VFIO_BASE + 17)
+
 /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
 
 /*
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
                   ` (2 preceding siblings ...)
  2020-03-19 20:16 ` [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  2020-03-19 22:57   ` Alex Williamson
  2020-03-19 20:16 ` [PATCH v15 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Kirti Wankhede
                   ` (2 subsequent siblings)
  6 siblings, 1 reply; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
- Start dirty pages tracking while migration is active
- Stop dirty pages tracking.
- Get dirty pages bitmap. Its user space application's responsibility to
  copy content of dirty pages from source to destination during migration.

To prevent DoS attack, memory for bitmap is allocated per vfio_dma
structure. Bitmap size is calculated considering smallest supported page
size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled

Bitmap is populated for already pinned pages when bitmap is allocated for
a vfio_dma with the smallest supported page size. Update bitmap from
pinning functions when tracking is enabled. When user application queries
bitmap, check if requested page size is same as page size used to
populated bitmap. If it is equal, copy bitmap, but if not equal, return
error.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 242 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 236 insertions(+), 6 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 70aeab921d0f..239f61764d03 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -71,6 +71,7 @@ struct vfio_iommu {
 	unsigned int		dma_avail;
 	bool			v2;
 	bool			nesting;
+	bool			dirty_page_tracking;
 };
 
 struct vfio_domain {
@@ -91,6 +92,7 @@ struct vfio_dma {
 	bool			lock_cap;	/* capable(CAP_IPC_LOCK) */
 	struct task_struct	*task;
 	struct rb_root		pfn_list;	/* Ex-user pinned pfn list */
+	unsigned long		*bitmap;
 };
 
 struct vfio_group {
@@ -125,7 +127,21 @@ struct vfio_regions {
 #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
 					(!list_empty(&iommu->domain_list))
 
+#define DIRTY_BITMAP_BYTES(n)	(ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE)
+
+/*
+ * Input argument of number of bits to bitmap_set() is unsigned integer, which
+ * further casts to signed integer for unaligned multi-bit operation,
+ * __bitmap_set().
+ * Then maximum bitmap size supported is 2^31 bits divided by 2^3 bits/byte,
+ * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page
+ * system.
+ */
+#define DIRTY_BITMAP_PAGES_MAX	((1UL << 31) - 1)
+#define DIRTY_BITMAP_SIZE_MAX	 DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
+
 static int put_pfn(unsigned long pfn, int prot);
+static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
 
 /*
  * This code handles mapping and unmapping of user data buffers
@@ -175,6 +191,67 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
 	rb_erase(&old->node, &iommu->dma_list);
 }
 
+
+static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, uint64_t pgsize)
+{
+	uint64_t npages = dma->size / pgsize;
+
+	dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL);
+	if (!dma->bitmap)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, uint64_t pgsize)
+{
+	struct rb_node *n = rb_first(&iommu->dma_list);
+
+	for (; n; n = rb_next(n)) {
+		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
+		struct rb_node *p;
+		int ret;
+
+		ret = vfio_dma_bitmap_alloc(dma, pgsize);
+		if (ret) {
+			struct rb_node *p = rb_prev(n);
+
+			for (; p; p = rb_prev(p)) {
+				struct vfio_dma *dma = rb_entry(n,
+							struct vfio_dma, node);
+
+				kfree(dma->bitmap);
+				dma->bitmap = NULL;
+			}
+			return ret;
+		}
+
+		if (RB_EMPTY_ROOT(&dma->pfn_list))
+			continue;
+
+		for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) {
+			struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn,
+							 node);
+
+			bitmap_set(dma->bitmap,
+				   (vpfn->iova - dma->iova) / pgsize, 1);
+		}
+	}
+	return 0;
+}
+
+static void vfio_dma_bitmap_free_all(struct vfio_iommu *iommu)
+{
+	struct rb_node *n = rb_first(&iommu->dma_list);
+
+	for (; n; n = rb_next(n)) {
+		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
+
+		kfree(dma->bitmap);
+		dma->bitmap = NULL;
+	}
+}
+
 /*
  * Helper Functions for host iova-pfn list
  */
@@ -567,6 +644,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 			vfio_unpin_page_external(dma, iova, do_accounting);
 			goto pin_unwind;
 		}
+
+		if (iommu->dirty_page_tracking) {
+			unsigned long pgshift =
+					 __ffs(vfio_pgsize_bitmap(iommu));
+
+			bitmap_set(dma->bitmap,
+				   (vpfn->iova - dma->iova) >> pgshift, 1);
+		}
 	}
 
 	ret = i;
@@ -801,6 +886,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
 	vfio_unmap_unpin(iommu, dma, true);
 	vfio_unlink_dma(iommu, dma);
 	put_task_struct(dma->task);
+	kfree(dma->bitmap);
 	kfree(dma);
 	iommu->dma_avail++;
 }
@@ -831,6 +917,50 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
 	return bitmap;
 }
 
+static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
+				  size_t size, uint64_t pgsize,
+				  u64 __user *bitmap)
+{
+	struct vfio_dma *dma;
+	unsigned long pgshift = __ffs(pgsize);
+	unsigned int npages, bitmap_size;
+
+	dma = vfio_find_dma(iommu, iova, 1);
+
+	if (!dma)
+		return -EINVAL;
+
+	if (dma->iova != iova || dma->size != size)
+		return -EINVAL;
+
+	npages = dma->size >> pgshift;
+	bitmap_size = DIRTY_BITMAP_BYTES(npages);
+
+	/* mark all pages dirty if all pages are pinned and mapped. */
+	if (dma->iommu_mapped)
+		bitmap_set(dma->bitmap, 0, npages);
+
+	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
+{
+	uint64_t bsize;
+
+	if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_MAX))
+		return -EINVAL;
+
+	bsize = DIRTY_BITMAP_BYTES(npages);
+
+	if (bitmap_size < bsize)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 			     struct vfio_iommu_type1_dma_unmap *unmap)
 {
@@ -1038,16 +1168,16 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	unsigned long vaddr = map->vaddr;
 	size_t size = map->size;
 	int ret = 0, prot = 0;
-	uint64_t mask;
+	uint64_t pgsize;
 	struct vfio_dma *dma;
 
 	/* Verify that none of our __u64 fields overflow */
 	if (map->size != size || map->vaddr != vaddr || map->iova != iova)
 		return -EINVAL;
 
-	mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
+	pgsize = (uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu));
 
-	WARN_ON(mask & PAGE_MASK);
+	WARN_ON((pgsize - 1) & PAGE_MASK);
 
 	/* READ/WRITE from device perspective */
 	if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
@@ -1055,7 +1185,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	if (map->flags & VFIO_DMA_MAP_FLAG_READ)
 		prot |= IOMMU_READ;
 
-	if (!prot || !size || (size | iova | vaddr) & mask)
+	if (!prot || !size || (size | iova | vaddr) & (pgsize - 1))
 		return -EINVAL;
 
 	/* Don't allow IOVA or virtual address wrap */
@@ -1130,6 +1260,12 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	else
 		ret = vfio_pin_map_dma(iommu, dma, size);
 
+	if (!ret && iommu->dirty_page_tracking) {
+		ret = vfio_dma_bitmap_alloc(dma, pgsize);
+		if (ret)
+			vfio_remove_dma(iommu, dma);
+	}
+
 out_unlock:
 	mutex_unlock(&iommu->lock);
 	return ret;
@@ -2278,6 +2414,93 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 		return copy_to_user((void __user *)arg, &unmap, minsz) ?
 			-EFAULT : 0;
+	} else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
+		struct vfio_iommu_type1_dirty_bitmap dirty;
+		uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
+				VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP |
+				VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
+		int ret = 0;
+
+		if (!iommu->v2)
+			return -EACCES;
+
+		minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap,
+				    flags);
+
+		if (copy_from_user(&dirty, (void __user *)arg, minsz))
+			return -EFAULT;
+
+		if (dirty.argsz < minsz || dirty.flags & ~mask)
+			return -EINVAL;
+
+		/* only one flag should be set at a time */
+		if (__ffs(dirty.flags) != __fls(dirty.flags))
+			return -EINVAL;
+
+		if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
+			uint64_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu));
+
+			mutex_lock(&iommu->lock);
+			if (!iommu->dirty_page_tracking) {
+				ret = vfio_dma_bitmap_alloc_all(iommu, pgsize);
+				if (!ret)
+					iommu->dirty_page_tracking = true;
+			}
+			mutex_unlock(&iommu->lock);
+			return ret;
+		} else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
+			mutex_lock(&iommu->lock);
+			if (iommu->dirty_page_tracking) {
+				iommu->dirty_page_tracking = false;
+				vfio_dma_bitmap_free_all(iommu);
+			}
+			mutex_unlock(&iommu->lock);
+			return 0;
+		} else if (dirty.flags &
+				 VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
+			struct vfio_iommu_type1_dirty_bitmap_get range;
+			unsigned long pgshift;
+			size_t data_size = dirty.argsz - minsz;
+			uint64_t iommu_pgsize =
+					 1 << __ffs(vfio_pgsize_bitmap(iommu));
+
+			if (!data_size || data_size < sizeof(range))
+				return -EINVAL;
+
+			if (copy_from_user(&range, (void __user *)(arg + minsz),
+					   sizeof(range)))
+				return -EFAULT;
+
+			/* allow only min supported pgsize */
+			if (range.bitmap.pgsize != iommu_pgsize)
+				return -EINVAL;
+			if (range.iova & (iommu_pgsize - 1))
+				return -EINVAL;
+			if (!range.size || range.size & (iommu_pgsize - 1))
+				return -EINVAL;
+			if (range.iova + range.size < range.iova)
+				return -EINVAL;
+			if (!access_ok((void __user *)range.bitmap.data,
+				       range.bitmap.size))
+				return -EINVAL;
+
+			pgshift = __ffs(range.bitmap.pgsize);
+			ret = verify_bitmap_size(range.size >> pgshift,
+						 range.bitmap.size);
+			if (ret)
+				return ret;
+
+			mutex_lock(&iommu->lock);
+			if (iommu->dirty_page_tracking)
+				ret = vfio_iova_dirty_bitmap(iommu, range.iova,
+						range.size, range.bitmap.pgsize,
+						range.bitmap.data);
+			else
+				ret = -EINVAL;
+			mutex_unlock(&iommu->lock);
+
+			return ret;
+		}
 	}
 
 	return -ENOTTY;
@@ -2345,10 +2568,17 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
 
 	vaddr = dma->vaddr + offset;
 
-	if (write)
+	if (write) {
 		*copied = __copy_to_user((void __user *)vaddr, data,
 					 count) ? 0 : count;
-	else
+		if (*copied && iommu->dirty_page_tracking) {
+			unsigned long pgshift =
+				__ffs(vfio_pgsize_bitmap(iommu));
+
+			bitmap_set(dma->bitmap, offset >> pgshift,
+				   *copied >> pgshift);
+		}
+	} else
 		*copied = __copy_from_user(data, (void __user *)vaddr,
 					   count) ? 0 : count;
 	if (kthread)
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
                   ` (3 preceding siblings ...)
  2020-03-19 20:16 ` [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages Kirti Wankhede
  6 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

DMA mapped pages, including those pinned by mdev vendor drivers, might
get unpinned and unmapped while migration is active and device is still
running. For example, in pre-copy phase while guest driver could access
those pages, host device or vendor driver can dirty these mapped pages.
Such pages should be marked dirty so as to maintain memory consistency
for a user making use of dirty page tracking.

To get bitmap during unmap, user should allocate memory for bitmap, set
size of allocated memory, set page size to be considered for bitmap and
set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 54 ++++++++++++++++++++++++++++++++++++++---
 include/uapi/linux/vfio.h       | 10 ++++++++
 2 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 239f61764d03..e79c1ff6fb41 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -962,7 +962,8 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
 }
 
 static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
-			     struct vfio_iommu_type1_dma_unmap *unmap)
+			     struct vfio_iommu_type1_dma_unmap *unmap,
+			     struct vfio_bitmap *bitmap)
 {
 	uint64_t mask;
 	struct vfio_dma *dma, *dma_last = NULL;
@@ -1013,6 +1014,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 	 * will be returned if these conditions are not met.  The v2 interface
 	 * will only return success and a size of zero if there were no
 	 * mappings within the range.
+	 *
+	 * When VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP flag is set, unmap request
+	 * must be for single mapping. Multiple mappings with this flag set is
+	 * not supported.
 	 */
 	if (iommu->v2) {
 		dma = vfio_find_dma(iommu, unmap->iova, 1);
@@ -1020,6 +1025,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 			ret = -EINVAL;
 			goto unlock;
 		}
+
+		if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) &&
+		    (dma->iova != unmap->iova || dma->size != unmap->size)) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+
 		dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0);
 		if (dma && dma->iova + dma->size != unmap->iova + unmap->size) {
 			ret = -EINVAL;
@@ -1037,6 +1049,11 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 		if (dma->task->mm != current->mm)
 			break;
 
+		if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) &&
+		     iommu->dirty_page_tracking)
+			vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size,
+						bitmap->pgsize, bitmap->data);
+
 		if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
 			struct vfio_iommu_type1_dma_unmap nb_unmap;
 
@@ -2398,17 +2415,46 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 	} else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
 		struct vfio_iommu_type1_dma_unmap unmap;
-		long ret;
+		struct vfio_bitmap bitmap = { 0 };
+		int ret;
 
 		minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size);
 
 		if (copy_from_user(&unmap, (void __user *)arg, minsz))
 			return -EFAULT;
 
-		if (unmap.argsz < minsz || unmap.flags)
+		if (unmap.argsz < minsz ||
+		    unmap.flags & ~VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP)
 			return -EINVAL;
 
-		ret = vfio_dma_do_unmap(iommu, &unmap);
+		if (unmap.flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) {
+			unsigned long pgshift;
+			uint64_t iommu_pgsize =
+					 1 << __ffs(vfio_pgsize_bitmap(iommu));
+
+			if (unmap.argsz < (minsz + sizeof(bitmap)))
+				return -EINVAL;
+
+			if (copy_from_user(&bitmap,
+					   (void __user *)(arg + minsz),
+					   sizeof(bitmap)))
+				return -EFAULT;
+
+			/* allow only min supported pgsize */
+			if (bitmap.pgsize != iommu_pgsize)
+				return -EINVAL;
+			if (!access_ok((void __user *)bitmap.data, bitmap.size))
+				return -EINVAL;
+
+			pgshift = __ffs(bitmap.pgsize);
+			ret = verify_bitmap_size(unmap.size >> pgshift,
+						 bitmap.size);
+			if (ret)
+				return ret;
+
+		}
+
+		ret = vfio_dma_do_unmap(iommu, &unmap, &bitmap);
 		if (ret)
 			return ret;
 
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 8138f94cac15..2780a5742c04 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -1010,12 +1010,22 @@ struct vfio_bitmap {
  * field.  No guarantee is made to the user that arbitrary unmaps of iova
  * or size different from those used in the original mapping call will
  * succeed.
+ * VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP should be set to get dirty bitmap
+ * before unmapping IO virtual addresses. When this flag is set, user must
+ * provide data[] as structure vfio_bitmap. User must allocate memory to get
+ * bitmap and must set size of allocated memory in vfio_bitmap.size field.
+ * A bit in bitmap represents one page of user provided page size in 'pgsize',
+ * consecutively starting from iova offset. Bit set indicates page at that
+ * offset from iova is dirty. Bitmap of pages in the range of unmapped size is
+ * returned in vfio_bitmap.data
  */
 struct vfio_iommu_type1_dma_unmap {
 	__u32	argsz;
 	__u32	flags;
+#define VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP (1 << 0)
 	__u64	iova;				/* IO virtual address */
 	__u64	size;				/* Size of mapping (bytes) */
+	__u8    data[];
 };
 
 #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
                   ` (4 preceding siblings ...)
  2020-03-19 20:16 ` [PATCH v15 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  2020-03-19 20:16 ` [PATCH v15 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages Kirti Wankhede
  6 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

Flag VFIO_IOMMU_INFO_DIRTY_PGS in VFIO_IOMMU_GET_INFO indicates that driver
support dirty pages tracking.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 3 ++-
 include/uapi/linux/vfio.h       | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index e79c1ff6fb41..dce0a3e1e8b7 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2368,7 +2368,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 			info.cap_offset = 0; /* output, no-recopy necessary */
 		}
 
-		info.flags = VFIO_IOMMU_INFO_PGSIZES;
+		info.flags = VFIO_IOMMU_INFO_PGSIZES |
+			     VFIO_IOMMU_INFO_DIRTY_PGS;
 
 		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
 
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 2780a5742c04..4a886ff84c92 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -947,8 +947,9 @@ struct vfio_device_ioeventfd {
 struct vfio_iommu_type1_info {
 	__u32	argsz;
 	__u32	flags;
-#define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
-#define VFIO_IOMMU_INFO_CAPS	(1 << 1)	/* Info supports caps */
+#define VFIO_IOMMU_INFO_PGSIZES   (1 << 0) /* supported page sizes info */
+#define VFIO_IOMMU_INFO_CAPS      (1 << 1) /* Info supports caps */
+#define VFIO_IOMMU_INFO_DIRTY_PGS (1 << 2) /* supports dirty page tracking */
 	__u64	iova_pgsizes;	/* Bitmap of supported page sizes */
 	__u32   cap_offset;	/* Offset within info struct of first cap */
 };
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* [PATCH v15 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages
  2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
                   ` (5 preceding siblings ...)
  2020-03-19 20:16 ` [PATCH v15 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Kirti Wankhede
@ 2020-03-19 20:16 ` Kirti Wankhede
  6 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-19 20:16 UTC (permalink / raw)
  To: alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

Added a check such that only singleton IOMMU groups can pin pages.
From the point when vendor driver pins any pages, consider IOMMU group
dirty page scope to be limited to pinned pages.

To optimize to avoid walking list often, added flag
pinned_page_dirty_scope to indicate if all of the vfio_groups for each
vfio_domain in the domain_list dirty page scope is limited to pinned
pages. This flag is updated on first pinned pages request for that IOMMU
group and on attaching/detaching group.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio.c             | 13 ++++--
 drivers/vfio/vfio_iommu_type1.c | 94 +++++++++++++++++++++++++++++++++++++++--
 include/linux/vfio.h            |  4 +-
 3 files changed, 104 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 210fcf426643..311b5e4e111e 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -85,6 +85,7 @@ struct vfio_group {
 	atomic_t			opened;
 	wait_queue_head_t		container_q;
 	bool				noiommu;
+	unsigned int			dev_counter;
 	struct kvm			*kvm;
 	struct blocking_notifier_head	notifier;
 };
@@ -555,6 +556,7 @@ struct vfio_device *vfio_group_create_device(struct vfio_group *group,
 
 	mutex_lock(&group->device_lock);
 	list_add(&device->group_next, &group->device_list);
+	group->dev_counter++;
 	mutex_unlock(&group->device_lock);
 
 	return device;
@@ -567,6 +569,7 @@ static void vfio_device_release(struct kref *kref)
 	struct vfio_group *group = device->group;
 
 	list_del(&device->group_next);
+	group->dev_counter--;
 	mutex_unlock(&group->device_lock);
 
 	dev_set_drvdata(device->dev, NULL);
@@ -1933,6 +1936,9 @@ int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage,
 	if (!group)
 		return -ENODEV;
 
+	if (group->dev_counter > 1)
+		return -EINVAL;
+
 	ret = vfio_group_add_container_user(group);
 	if (ret)
 		goto err_pin_pages;
@@ -1940,7 +1946,8 @@ int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage,
 	container = group->container;
 	driver = container->iommu_driver;
 	if (likely(driver && driver->ops->pin_pages))
-		ret = driver->ops->pin_pages(container->iommu_data, user_pfn,
+		ret = driver->ops->pin_pages(container->iommu_data,
+					     group->iommu_group, user_pfn,
 					     npage, prot, phys_pfn);
 	else
 		ret = -ENOTTY;
@@ -2038,8 +2045,8 @@ int vfio_group_pin_pages(struct vfio_group *group,
 	driver = container->iommu_driver;
 	if (likely(driver && driver->ops->pin_pages))
 		ret = driver->ops->pin_pages(container->iommu_data,
-					     user_iova_pfn, npage,
-					     prot, phys_pfn);
+					     group->iommu_group, user_iova_pfn,
+					     npage, prot, phys_pfn);
 	else
 		ret = -ENOTTY;
 
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index dce0a3e1e8b7..881abfc04f0a 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -72,6 +72,7 @@ struct vfio_iommu {
 	bool			v2;
 	bool			nesting;
 	bool			dirty_page_tracking;
+	bool			pinned_page_dirty_scope;
 };
 
 struct vfio_domain {
@@ -99,6 +100,7 @@ struct vfio_group {
 	struct iommu_group	*iommu_group;
 	struct list_head	next;
 	bool			mdev_group;	/* An mdev group */
+	bool			pinned_page_dirty_scope;
 };
 
 struct vfio_iova {
@@ -143,6 +145,10 @@ struct vfio_regions {
 static int put_pfn(unsigned long pfn, int prot);
 static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
 
+static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
+					       struct iommu_group *iommu_group);
+
+static void update_pinned_page_dirty_scope(struct vfio_iommu *iommu);
 /*
  * This code handles mapping and unmapping of user data buffers
  * into DMA'ble space using the IOMMU
@@ -579,11 +585,13 @@ static int vfio_unpin_page_external(struct vfio_dma *dma, dma_addr_t iova,
 }
 
 static int vfio_iommu_type1_pin_pages(void *iommu_data,
+				      struct iommu_group *iommu_group,
 				      unsigned long *user_pfn,
 				      int npage, int prot,
 				      unsigned long *phys_pfn)
 {
 	struct vfio_iommu *iommu = iommu_data;
+	struct vfio_group *group;
 	int i, j, ret;
 	unsigned long remote_vaddr;
 	struct vfio_dma *dma;
@@ -653,8 +661,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 				   (vpfn->iova - dma->iova) >> pgshift, 1);
 		}
 	}
-
 	ret = i;
+
+	group = vfio_iommu_find_iommu_group(iommu, iommu_group);
+	if (!group->pinned_page_dirty_scope) {
+		group->pinned_page_dirty_scope = true;
+		update_pinned_page_dirty_scope(iommu);
+	}
+
 	goto pin_done;
 
 pin_unwind:
@@ -936,8 +950,11 @@ static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
 	npages = dma->size >> pgshift;
 	bitmap_size = DIRTY_BITMAP_BYTES(npages);
 
-	/* mark all pages dirty if all pages are pinned and mapped. */
-	if (dma->iommu_mapped)
+	/*
+	 * mark all pages dirty if any IOMMU capable device is not able
+	 * to report dirty pages and all pages are pinned and mapped.
+	 */
+	if (!iommu->pinned_page_dirty_scope && dma->iommu_mapped)
 		bitmap_set(dma->bitmap, 0, npages);
 
 	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
@@ -1421,6 +1438,51 @@ static struct vfio_group *find_iommu_group(struct vfio_domain *domain,
 	return NULL;
 }
 
+static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
+					       struct iommu_group *iommu_group)
+{
+	struct vfio_domain *domain;
+	struct vfio_group *group = NULL;
+
+	list_for_each_entry(domain, &iommu->domain_list, next) {
+		group = find_iommu_group(domain, iommu_group);
+		if (group)
+			return group;
+	}
+
+	if (iommu->external_domain)
+		group = find_iommu_group(iommu->external_domain, iommu_group);
+
+	return group;
+}
+
+static void update_pinned_page_dirty_scope(struct vfio_iommu *iommu)
+{
+	struct vfio_domain *domain;
+	struct vfio_group *group;
+
+	list_for_each_entry(domain, &iommu->domain_list, next) {
+		list_for_each_entry(group, &domain->group_list, next) {
+			if (!group->pinned_page_dirty_scope) {
+				iommu->pinned_page_dirty_scope = false;
+				return;
+			}
+		}
+	}
+
+	if (iommu->external_domain) {
+		domain = iommu->external_domain;
+		list_for_each_entry(group, &domain->group_list, next) {
+			if (!group->pinned_page_dirty_scope) {
+				iommu->pinned_page_dirty_scope = false;
+				return;
+			}
+		}
+	}
+
+	iommu->pinned_page_dirty_scope = true;
+}
+
 static bool vfio_iommu_has_sw_msi(struct list_head *group_resv_regions,
 				  phys_addr_t *base)
 {
@@ -1827,6 +1889,16 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 
 			list_add(&group->next,
 				 &iommu->external_domain->group_list);
+			/*
+			 * Non-iommu backed group cannot dirty memory directly,
+			 * it can only use interfaces that provide dirty
+			 * tracking.
+			 * The iommu scope can only be promoted with the
+			 * addition of a dirty tracking group.
+			 */
+			group->pinned_page_dirty_scope = true;
+			if (!iommu->pinned_page_dirty_scope)
+				update_pinned_page_dirty_scope(iommu);
 			mutex_unlock(&iommu->lock);
 
 			return 0;
@@ -1949,6 +2021,13 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 done:
 	/* Delete the old one and insert new iova list */
 	vfio_iommu_iova_insert_copy(iommu, &iova_copy);
+
+	/*
+	 * An iommu backed group can dirty memory directly and therefore
+	 * demotes the iommu scope until it declares itself dirty tracking
+	 * capable via the page pinning interface.
+	 */
+	iommu->pinned_page_dirty_scope = false;
 	mutex_unlock(&iommu->lock);
 	vfio_iommu_resv_free(&group_resv_regions);
 
@@ -2101,6 +2180,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 	struct vfio_iommu *iommu = iommu_data;
 	struct vfio_domain *domain;
 	struct vfio_group *group;
+	bool update_dirty_scope = false;
 	LIST_HEAD(iova_copy);
 
 	mutex_lock(&iommu->lock);
@@ -2108,6 +2188,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 	if (iommu->external_domain) {
 		group = find_iommu_group(iommu->external_domain, iommu_group);
 		if (group) {
+			update_dirty_scope = !group->pinned_page_dirty_scope;
 			list_del(&group->next);
 			kfree(group);
 
@@ -2137,6 +2218,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 			continue;
 
 		vfio_iommu_detach_group(domain, group);
+		update_dirty_scope = !group->pinned_page_dirty_scope;
 		list_del(&group->next);
 		kfree(group);
 		/*
@@ -2167,6 +2249,12 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 		vfio_iommu_iova_free(&iova_copy);
 
 detach_group_done:
+	/*
+	 * Removal of a group without dirty tracking may allow the iommu scope
+	 * to be promoted.
+	 */
+	if (update_dirty_scope)
+		update_pinned_page_dirty_scope(iommu);
 	mutex_unlock(&iommu->lock);
 }
 
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index be2bd358b952..702e1d7b6e8b 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -72,7 +72,9 @@ struct vfio_iommu_driver_ops {
 					struct iommu_group *group);
 	void		(*detach_group)(void *iommu_data,
 					struct iommu_group *group);
-	int		(*pin_pages)(void *iommu_data, unsigned long *user_pfn,
+	int		(*pin_pages)(void *iommu_data,
+				     struct iommu_group *group,
+				     unsigned long *user_pfn,
 				     int npage, int prot,
 				     unsigned long *phys_pfn);
 	int		(*unpin_pages)(void *iommu_data,
-- 
2.7.0



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-19 20:16 ` [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
@ 2020-03-19 22:57   ` Alex Williamson
  2020-03-20 17:49     ` Kirti Wankhede
  0 siblings, 1 reply; 29+ messages in thread
From: Alex Williamson @ 2020-03-19 22:57 UTC (permalink / raw)
  To: Kirti Wankhede
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue

On Fri, 20 Mar 2020 01:46:41 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
> - Start dirty pages tracking while migration is active
> - Stop dirty pages tracking.
> - Get dirty pages bitmap. Its user space application's responsibility to
>   copy content of dirty pages from source to destination during migration.
> 
> To prevent DoS attack, memory for bitmap is allocated per vfio_dma
> structure. Bitmap size is calculated considering smallest supported page
> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled
> 
> Bitmap is populated for already pinned pages when bitmap is allocated for
> a vfio_dma with the smallest supported page size. Update bitmap from
> pinning functions when tracking is enabled. When user application queries
> bitmap, check if requested page size is same as page size used to
> populated bitmap. If it is equal, copy bitmap, but if not equal, return
> error.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 242 +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 236 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 70aeab921d0f..239f61764d03 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -71,6 +71,7 @@ struct vfio_iommu {
>  	unsigned int		dma_avail;
>  	bool			v2;
>  	bool			nesting;
> +	bool			dirty_page_tracking;
>  };
>  
>  struct vfio_domain {
> @@ -91,6 +92,7 @@ struct vfio_dma {
>  	bool			lock_cap;	/* capable(CAP_IPC_LOCK) */
>  	struct task_struct	*task;
>  	struct rb_root		pfn_list;	/* Ex-user pinned pfn list */
> +	unsigned long		*bitmap;
>  };
>  
>  struct vfio_group {
> @@ -125,7 +127,21 @@ struct vfio_regions {
>  #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
>  					(!list_empty(&iommu->domain_list))
>  
> +#define DIRTY_BITMAP_BYTES(n)	(ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE)
> +
> +/*
> + * Input argument of number of bits to bitmap_set() is unsigned integer, which
> + * further casts to signed integer for unaligned multi-bit operation,
> + * __bitmap_set().
> + * Then maximum bitmap size supported is 2^31 bits divided by 2^3 bits/byte,
> + * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page
> + * system.
> + */
> +#define DIRTY_BITMAP_PAGES_MAX	((1UL << 31) - 1)
> +#define DIRTY_BITMAP_SIZE_MAX	 DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
> +
>  static int put_pfn(unsigned long pfn, int prot);
> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
>  
>  /*
>   * This code handles mapping and unmapping of user data buffers
> @@ -175,6 +191,67 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
>  	rb_erase(&old->node, &iommu->dma_list);
>  }
>  
> +
> +static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, uint64_t pgsize)
> +{
> +	uint64_t npages = dma->size / pgsize;
> +

Shouldn't we test this against one of the MAX macros defined above?  It
would be bad if we could enabled dirty tracking but not allow the user
to retrieve it.

> +	dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL);
> +	if (!dma->bitmap)
> +		return -ENOMEM;
> +
> +	return 0;
> +}
> +
> +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, uint64_t pgsize)
> +{
> +	struct rb_node *n = rb_first(&iommu->dma_list);
> +
> +	for (; n; n = rb_next(n)) {
> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> +		struct rb_node *p;
> +		int ret;
> +
> +		ret = vfio_dma_bitmap_alloc(dma, pgsize);
> +		if (ret) {
> +			struct rb_node *p = rb_prev(n);
> +
> +			for (; p; p = rb_prev(p)) {
> +				struct vfio_dma *dma = rb_entry(n,
> +							struct vfio_dma, node);
> +
> +				kfree(dma->bitmap);
> +				dma->bitmap = NULL;
> +			}
> +			return ret;
> +		}
> +
> +		if (RB_EMPTY_ROOT(&dma->pfn_list))
> +			continue;
> +
> +		for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) {
> +			struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn,
> +							 node);
> +
> +			bitmap_set(dma->bitmap,
> +				   (vpfn->iova - dma->iova) / pgsize, 1);
> +		}
> +	}
> +	return 0;
> +}
> +
> +static void vfio_dma_bitmap_free_all(struct vfio_iommu *iommu)
> +{
> +	struct rb_node *n = rb_first(&iommu->dma_list);
> +
> +	for (; n; n = rb_next(n)) {
> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> +
> +		kfree(dma->bitmap);
> +		dma->bitmap = NULL;

Might be useful to have a vfio_dma_bitmap_free() for here and above.

> +	}
> +}
> +
>  /*
>   * Helper Functions for host iova-pfn list
>   */
> @@ -567,6 +644,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>  			vfio_unpin_page_external(dma, iova, do_accounting);
>  			goto pin_unwind;
>  		}
> +
> +		if (iommu->dirty_page_tracking) {
> +			unsigned long pgshift =
> +					 __ffs(vfio_pgsize_bitmap(iommu));
> +
> +			bitmap_set(dma->bitmap,
> +				   (vpfn->iova - dma->iova) >> pgshift, 1);
> +		}
>  	}
>  
>  	ret = i;
> @@ -801,6 +886,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
>  	vfio_unmap_unpin(iommu, dma, true);
>  	vfio_unlink_dma(iommu, dma);
>  	put_task_struct(dma->task);
> +	kfree(dma->bitmap);
>  	kfree(dma);
>  	iommu->dma_avail++;
>  }
> @@ -831,6 +917,50 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
>  	return bitmap;
>  }
>  
> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> +				  size_t size, uint64_t pgsize,
> +				  u64 __user *bitmap)
> +{
> +	struct vfio_dma *dma;
> +	unsigned long pgshift = __ffs(pgsize);
> +	unsigned int npages, bitmap_size;
> +
> +	dma = vfio_find_dma(iommu, iova, 1);
> +
> +	if (!dma)
> +		return -EINVAL;
> +
> +	if (dma->iova != iova || dma->size != size)
> +		return -EINVAL;
> +
> +	npages = dma->size >> pgshift;
> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> +
> +	/* mark all pages dirty if all pages are pinned and mapped. */
> +	if (dma->iommu_mapped)
> +		bitmap_set(dma->bitmap, 0, npages);
> +
> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> +		return -EFAULT;

We still need to reset the bitmap here, clearing and re-adding the
pages that are still pinned.

https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/

> +
> +	return 0;
> +}
> +
> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> +{
> +	uint64_t bsize;
> +
> +	if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_MAX))
> +		return -EINVAL;
> +
> +	bsize = DIRTY_BITMAP_BYTES(npages);
> +
> +	if (bitmap_size < bsize)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  			     struct vfio_iommu_type1_dma_unmap *unmap)
>  {
> @@ -1038,16 +1168,16 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>  	unsigned long vaddr = map->vaddr;
>  	size_t size = map->size;
>  	int ret = 0, prot = 0;
> -	uint64_t mask;
> +	uint64_t pgsize;
>  	struct vfio_dma *dma;
>  
>  	/* Verify that none of our __u64 fields overflow */
>  	if (map->size != size || map->vaddr != vaddr || map->iova != iova)
>  		return -EINVAL;
>  
> -	mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> +	pgsize = (uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu));
>  
> -	WARN_ON(mask & PAGE_MASK);
> +	WARN_ON((pgsize - 1) & PAGE_MASK);
>  
>  	/* READ/WRITE from device perspective */
>  	if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
> @@ -1055,7 +1185,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>  	if (map->flags & VFIO_DMA_MAP_FLAG_READ)
>  		prot |= IOMMU_READ;
>  
> -	if (!prot || !size || (size | iova | vaddr) & mask)
> +	if (!prot || !size || (size | iova | vaddr) & (pgsize - 1))
>  		return -EINVAL;
>  
>  	/* Don't allow IOVA or virtual address wrap */
> @@ -1130,6 +1260,12 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>  	else
>  		ret = vfio_pin_map_dma(iommu, dma, size);
>  
> +	if (!ret && iommu->dirty_page_tracking) {
> +		ret = vfio_dma_bitmap_alloc(dma, pgsize);
> +		if (ret)
> +			vfio_remove_dma(iommu, dma);
> +	}
> +
>  out_unlock:
>  	mutex_unlock(&iommu->lock);
>  	return ret;
> @@ -2278,6 +2414,93 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  
>  		return copy_to_user((void __user *)arg, &unmap, minsz) ?
>  			-EFAULT : 0;
> +	} else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
> +		struct vfio_iommu_type1_dirty_bitmap dirty;
> +		uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
> +				VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP |
> +				VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
> +		int ret = 0;
> +
> +		if (!iommu->v2)
> +			return -EACCES;
> +
> +		minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap,
> +				    flags);
> +
> +		if (copy_from_user(&dirty, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (dirty.argsz < minsz || dirty.flags & ~mask)
> +			return -EINVAL;
> +
> +		/* only one flag should be set at a time */
> +		if (__ffs(dirty.flags) != __fls(dirty.flags))
> +			return -EINVAL;
> +
> +		if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> +			uint64_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu));
> +
> +			mutex_lock(&iommu->lock);
> +			if (!iommu->dirty_page_tracking) {
> +				ret = vfio_dma_bitmap_alloc_all(iommu, pgsize);
> +				if (!ret)
> +					iommu->dirty_page_tracking = true;
> +			}
> +			mutex_unlock(&iommu->lock);
> +			return ret;
> +		} else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
> +			mutex_lock(&iommu->lock);
> +			if (iommu->dirty_page_tracking) {
> +				iommu->dirty_page_tracking = false;
> +				vfio_dma_bitmap_free_all(iommu);
> +			}
> +			mutex_unlock(&iommu->lock);
> +			return 0;
> +		} else if (dirty.flags &
> +				 VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
> +			struct vfio_iommu_type1_dirty_bitmap_get range;
> +			unsigned long pgshift;
> +			size_t data_size = dirty.argsz - minsz;
> +			uint64_t iommu_pgsize =
> +					 1 << __ffs(vfio_pgsize_bitmap(iommu));
> +
> +			if (!data_size || data_size < sizeof(range))
> +				return -EINVAL;
> +
> +			if (copy_from_user(&range, (void __user *)(arg + minsz),
> +					   sizeof(range)))
> +				return -EFAULT;
> +
> +			/* allow only min supported pgsize */
> +			if (range.bitmap.pgsize != iommu_pgsize)
> +				return -EINVAL;
> +			if (range.iova & (iommu_pgsize - 1))
> +				return -EINVAL;
> +			if (!range.size || range.size & (iommu_pgsize - 1))
> +				return -EINVAL;
> +			if (range.iova + range.size < range.iova)
> +				return -EINVAL;
> +			if (!access_ok((void __user *)range.bitmap.data,
> +				       range.bitmap.size))
> +				return -EINVAL;
> +
> +			pgshift = __ffs(range.bitmap.pgsize);
> +			ret = verify_bitmap_size(range.size >> pgshift,
> +						 range.bitmap.size);
> +			if (ret)
> +				return ret;
> +
> +			mutex_lock(&iommu->lock);
> +			if (iommu->dirty_page_tracking)
> +				ret = vfio_iova_dirty_bitmap(iommu, range.iova,
> +						range.size, range.bitmap.pgsize,
> +						range.bitmap.data);
> +			else
> +				ret = -EINVAL;
> +			mutex_unlock(&iommu->lock);
> +
> +			return ret;
> +		}
>  	}
>  
>  	return -ENOTTY;
> @@ -2345,10 +2568,17 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
>  
>  	vaddr = dma->vaddr + offset;
>  
> -	if (write)
> +	if (write) {
>  		*copied = __copy_to_user((void __user *)vaddr, data,
>  					 count) ? 0 : count;
> -	else
> +		if (*copied && iommu->dirty_page_tracking) {
> +			unsigned long pgshift =
> +				__ffs(vfio_pgsize_bitmap(iommu));
> +
> +			bitmap_set(dma->bitmap, offset >> pgshift,
> +				   *copied >> pgshift);
> +		}
> +	} else
>  		*copied = __copy_from_user(data, (void __user *)vaddr,
>  					   count) ? 0 : count;
>  	if (kthread)



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-19 22:57   ` Alex Williamson
@ 2020-03-20 17:49     ` Kirti Wankhede
  2020-03-20 18:01       ` Alex Williamson
  0 siblings, 1 reply; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-20 17:49 UTC (permalink / raw)
  To: Alex Williamson
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue



On 3/20/2020 4:27 AM, Alex Williamson wrote:
> On Fri, 20 Mar 2020 01:46:41 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
>> - Start dirty pages tracking while migration is active
>> - Stop dirty pages tracking.
>> - Get dirty pages bitmap. Its user space application's responsibility to
>>    copy content of dirty pages from source to destination during migration.
>>
>> To prevent DoS attack, memory for bitmap is allocated per vfio_dma
>> structure. Bitmap size is calculated considering smallest supported page
>> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled
>>
>> Bitmap is populated for already pinned pages when bitmap is allocated for
>> a vfio_dma with the smallest supported page size. Update bitmap from
>> pinning functions when tracking is enabled. When user application queries
>> bitmap, check if requested page size is same as page size used to
>> populated bitmap. If it is equal, copy bitmap, but if not equal, return
>> error.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>> ---
>>   drivers/vfio/vfio_iommu_type1.c | 242 +++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 236 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 70aeab921d0f..239f61764d03 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -71,6 +71,7 @@ struct vfio_iommu {
>>   	unsigned int		dma_avail;
>>   	bool			v2;
>>   	bool			nesting;
>> +	bool			dirty_page_tracking;
>>   };
>>   
>>   struct vfio_domain {
>> @@ -91,6 +92,7 @@ struct vfio_dma {
>>   	bool			lock_cap;	/* capable(CAP_IPC_LOCK) */
>>   	struct task_struct	*task;
>>   	struct rb_root		pfn_list;	/* Ex-user pinned pfn list */
>> +	unsigned long		*bitmap;
>>   };
>>   
>>   struct vfio_group {
>> @@ -125,7 +127,21 @@ struct vfio_regions {
>>   #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
>>   					(!list_empty(&iommu->domain_list))
>>   
>> +#define DIRTY_BITMAP_BYTES(n)	(ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE)
>> +
>> +/*
>> + * Input argument of number of bits to bitmap_set() is unsigned integer, which
>> + * further casts to signed integer for unaligned multi-bit operation,
>> + * __bitmap_set().
>> + * Then maximum bitmap size supported is 2^31 bits divided by 2^3 bits/byte,
>> + * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page
>> + * system.
>> + */
>> +#define DIRTY_BITMAP_PAGES_MAX	((1UL << 31) - 1)
>> +#define DIRTY_BITMAP_SIZE_MAX	 DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
>> +
>>   static int put_pfn(unsigned long pfn, int prot);
>> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
>>   
>>   /*
>>    * This code handles mapping and unmapping of user data buffers
>> @@ -175,6 +191,67 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
>>   	rb_erase(&old->node, &iommu->dma_list);
>>   }
>>   
>> +
>> +static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, uint64_t pgsize)
>> +{
>> +	uint64_t npages = dma->size / pgsize;
>> +
> 
> Shouldn't we test this against one of the MAX macros defined above?  It
> would be bad if we could enabled dirty tracking but not allow the user
> to retrieve it.
> 

Yes, adding check as below:

         if (npages > DIRTY_BITMAP_PAGES_MAX)
                 -EINVAL;


>> +	dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL);
>> +	if (!dma->bitmap)
>> +		return -ENOMEM;
>> +
>> +	return 0;
>> +}
>> +
>> +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, uint64_t pgsize)
>> +{
>> +	struct rb_node *n = rb_first(&iommu->dma_list);
>> +
>> +	for (; n; n = rb_next(n)) {
>> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
>> +		struct rb_node *p;
>> +		int ret;
>> +
>> +		ret = vfio_dma_bitmap_alloc(dma, pgsize);
>> +		if (ret) {
>> +			struct rb_node *p = rb_prev(n);
>> +
>> +			for (; p; p = rb_prev(p)) {
>> +				struct vfio_dma *dma = rb_entry(n,
>> +							struct vfio_dma, node);
>> +
>> +				kfree(dma->bitmap);
>> +				dma->bitmap = NULL;
>> +			}
>> +			return ret;
>> +		}
>> +
>> +		if (RB_EMPTY_ROOT(&dma->pfn_list))
>> +			continue;
>> +
>> +		for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) {
>> +			struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn,
>> +							 node);
>> +
>> +			bitmap_set(dma->bitmap,
>> +				   (vpfn->iova - dma->iova) / pgsize, 1);
>> +		}
>> +	}
>> +	return 0;
>> +}
>> +
>> +static void vfio_dma_bitmap_free_all(struct vfio_iommu *iommu)
>> +{
>> +	struct rb_node *n = rb_first(&iommu->dma_list);
>> +
>> +	for (; n; n = rb_next(n)) {
>> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
>> +
>> +		kfree(dma->bitmap);
>> +		dma->bitmap = NULL;
> 
> Might be useful to have a vfio_dma_bitmap_free() for here and above.
> 

Ok.

>> +	}
>> +}
>> +
>>   /*
>>    * Helper Functions for host iova-pfn list
>>    */
>> @@ -567,6 +644,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>>   			vfio_unpin_page_external(dma, iova, do_accounting);
>>   			goto pin_unwind;
>>   		}
>> +
>> +		if (iommu->dirty_page_tracking) {
>> +			unsigned long pgshift =
>> +					 __ffs(vfio_pgsize_bitmap(iommu));
>> +
>> +			bitmap_set(dma->bitmap,
>> +				   (vpfn->iova - dma->iova) >> pgshift, 1);
>> +		}
>>   	}
>>   
>>   	ret = i;
>> @@ -801,6 +886,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
>>   	vfio_unmap_unpin(iommu, dma, true);
>>   	vfio_unlink_dma(iommu, dma);
>>   	put_task_struct(dma->task);
>> +	kfree(dma->bitmap);
>>   	kfree(dma);
>>   	iommu->dma_avail++;
>>   }
>> @@ -831,6 +917,50 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
>>   	return bitmap;
>>   }
>>   
>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
>> +				  size_t size, uint64_t pgsize,
>> +				  u64 __user *bitmap)
>> +{
>> +	struct vfio_dma *dma;
>> +	unsigned long pgshift = __ffs(pgsize);
>> +	unsigned int npages, bitmap_size;
>> +
>> +	dma = vfio_find_dma(iommu, iova, 1);
>> +
>> +	if (!dma)
>> +		return -EINVAL;
>> +
>> +	if (dma->iova != iova || dma->size != size)
>> +		return -EINVAL;
>> +
>> +	npages = dma->size >> pgshift;
>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
>> +
>> +	/* mark all pages dirty if all pages are pinned and mapped. */
>> +	if (dma->iommu_mapped)
>> +		bitmap_set(dma->bitmap, 0, npages);
>> +
>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
>> +		return -EFAULT;
> 
> We still need to reset the bitmap here, clearing and re-adding the
> pages that are still pinned.
> 
> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> 

I thought you agreed on my reply to it
https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/

 > Why re-populate when there will be no change since
 > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
 > pin request while vfio_iova_dirty_bitmap() is still working, it will
 > wait till iommu->lock is released. Bitmap will be populated when page is
 > pinned.

Thanks,
Kirti

>> +
>> +	return 0;
>> +}
>> +
>> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
>> +{
>> +	uint64_t bsize;
>> +
>> +	if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_MAX))
>> +		return -EINVAL;
>> +
>> +	bsize = DIRTY_BITMAP_BYTES(npages);
>> +
>> +	if (bitmap_size < bsize)
>> +		return -EINVAL;
>> +
>> +	return 0;
>> +}
>> +
>>   static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>>   			     struct vfio_iommu_type1_dma_unmap *unmap)
>>   {
>> @@ -1038,16 +1168,16 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>>   	unsigned long vaddr = map->vaddr;
>>   	size_t size = map->size;
>>   	int ret = 0, prot = 0;
>> -	uint64_t mask;
>> +	uint64_t pgsize;
>>   	struct vfio_dma *dma;
>>   
>>   	/* Verify that none of our __u64 fields overflow */
>>   	if (map->size != size || map->vaddr != vaddr || map->iova != iova)
>>   		return -EINVAL;
>>   
>> -	mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
>> +	pgsize = (uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu));
>>   
>> -	WARN_ON(mask & PAGE_MASK);
>> +	WARN_ON((pgsize - 1) & PAGE_MASK);
>>   
>>   	/* READ/WRITE from device perspective */
>>   	if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
>> @@ -1055,7 +1185,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>>   	if (map->flags & VFIO_DMA_MAP_FLAG_READ)
>>   		prot |= IOMMU_READ;
>>   
>> -	if (!prot || !size || (size | iova | vaddr) & mask)
>> +	if (!prot || !size || (size | iova | vaddr) & (pgsize - 1))
>>   		return -EINVAL;
>>   
>>   	/* Don't allow IOVA or virtual address wrap */
>> @@ -1130,6 +1260,12 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>>   	else
>>   		ret = vfio_pin_map_dma(iommu, dma, size);
>>   
>> +	if (!ret && iommu->dirty_page_tracking) {
>> +		ret = vfio_dma_bitmap_alloc(dma, pgsize);
>> +		if (ret)
>> +			vfio_remove_dma(iommu, dma);
>> +	}
>> +
>>   out_unlock:
>>   	mutex_unlock(&iommu->lock);
>>   	return ret;
>> @@ -2278,6 +2414,93 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>>   
>>   		return copy_to_user((void __user *)arg, &unmap, minsz) ?
>>   			-EFAULT : 0;
>> +	} else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
>> +		struct vfio_iommu_type1_dirty_bitmap dirty;
>> +		uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
>> +				VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP |
>> +				VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
>> +		int ret = 0;
>> +
>> +		if (!iommu->v2)
>> +			return -EACCES;
>> +
>> +		minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap,
>> +				    flags);
>> +
>> +		if (copy_from_user(&dirty, (void __user *)arg, minsz))
>> +			return -EFAULT;
>> +
>> +		if (dirty.argsz < minsz || dirty.flags & ~mask)
>> +			return -EINVAL;
>> +
>> +		/* only one flag should be set at a time */
>> +		if (__ffs(dirty.flags) != __fls(dirty.flags))
>> +			return -EINVAL;
>> +
>> +		if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
>> +			uint64_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu));
>> +
>> +			mutex_lock(&iommu->lock);
>> +			if (!iommu->dirty_page_tracking) {
>> +				ret = vfio_dma_bitmap_alloc_all(iommu, pgsize);
>> +				if (!ret)
>> +					iommu->dirty_page_tracking = true;
>> +			}
>> +			mutex_unlock(&iommu->lock);
>> +			return ret;
>> +		} else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
>> +			mutex_lock(&iommu->lock);
>> +			if (iommu->dirty_page_tracking) {
>> +				iommu->dirty_page_tracking = false;
>> +				vfio_dma_bitmap_free_all(iommu);
>> +			}
>> +			mutex_unlock(&iommu->lock);
>> +			return 0;
>> +		} else if (dirty.flags &
>> +				 VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
>> +			struct vfio_iommu_type1_dirty_bitmap_get range;
>> +			unsigned long pgshift;
>> +			size_t data_size = dirty.argsz - minsz;
>> +			uint64_t iommu_pgsize =
>> +					 1 << __ffs(vfio_pgsize_bitmap(iommu));
>> +
>> +			if (!data_size || data_size < sizeof(range))
>> +				return -EINVAL;
>> +
>> +			if (copy_from_user(&range, (void __user *)(arg + minsz),
>> +					   sizeof(range)))
>> +				return -EFAULT;
>> +
>> +			/* allow only min supported pgsize */
>> +			if (range.bitmap.pgsize != iommu_pgsize)
>> +				return -EINVAL;
>> +			if (range.iova & (iommu_pgsize - 1))
>> +				return -EINVAL;
>> +			if (!range.size || range.size & (iommu_pgsize - 1))
>> +				return -EINVAL;
>> +			if (range.iova + range.size < range.iova)
>> +				return -EINVAL;
>> +			if (!access_ok((void __user *)range.bitmap.data,
>> +				       range.bitmap.size))
>> +				return -EINVAL;
>> +
>> +			pgshift = __ffs(range.bitmap.pgsize);
>> +			ret = verify_bitmap_size(range.size >> pgshift,
>> +						 range.bitmap.size);
>> +			if (ret)
>> +				return ret;
>> +
>> +			mutex_lock(&iommu->lock);
>> +			if (iommu->dirty_page_tracking)
>> +				ret = vfio_iova_dirty_bitmap(iommu, range.iova,
>> +						range.size, range.bitmap.pgsize,
>> +						range.bitmap.data);
>> +			else
>> +				ret = -EINVAL;
>> +			mutex_unlock(&iommu->lock);
>> +
>> +			return ret;
>> +		}
>>   	}
>>   
>>   	return -ENOTTY;
>> @@ -2345,10 +2568,17 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
>>   
>>   	vaddr = dma->vaddr + offset;
>>   
>> -	if (write)
>> +	if (write) {
>>   		*copied = __copy_to_user((void __user *)vaddr, data,
>>   					 count) ? 0 : count;
>> -	else
>> +		if (*copied && iommu->dirty_page_tracking) {
>> +			unsigned long pgshift =
>> +				__ffs(vfio_pgsize_bitmap(iommu));
>> +
>> +			bitmap_set(dma->bitmap, offset >> pgshift,
>> +				   *copied >> pgshift);
>> +		}
>> +	} else
>>   		*copied = __copy_from_user(data, (void __user *)vaddr,
>>   					   count) ? 0 : count;
>>   	if (kthread)
> 


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-20 17:49     ` Kirti Wankhede
@ 2020-03-20 18:01       ` Alex Williamson
  2020-03-20 18:42         ` Kirti Wankhede
  0 siblings, 1 reply; 29+ messages in thread
From: Alex Williamson @ 2020-03-20 18:01 UTC (permalink / raw)
  To: Kirti Wankhede
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue

On Fri, 20 Mar 2020 23:19:14 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 3/20/2020 4:27 AM, Alex Williamson wrote:
> > On Fri, 20 Mar 2020 01:46:41 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
> >> - Start dirty pages tracking while migration is active
> >> - Stop dirty pages tracking.
> >> - Get dirty pages bitmap. Its user space application's responsibility to
> >>    copy content of dirty pages from source to destination during migration.
> >>
> >> To prevent DoS attack, memory for bitmap is allocated per vfio_dma
> >> structure. Bitmap size is calculated considering smallest supported page
> >> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled
> >>
> >> Bitmap is populated for already pinned pages when bitmap is allocated for
> >> a vfio_dma with the smallest supported page size. Update bitmap from
> >> pinning functions when tracking is enabled. When user application queries
> >> bitmap, check if requested page size is same as page size used to
> >> populated bitmap. If it is equal, copy bitmap, but if not equal, return
> >> error.
> >>
> >> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> >> Reviewed-by: Neo Jia <cjia@nvidia.com>
> >> ---
> >>   drivers/vfio/vfio_iommu_type1.c | 242 +++++++++++++++++++++++++++++++++++++++-
> >>   1 file changed, 236 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> >> index 70aeab921d0f..239f61764d03 100644
> >> --- a/drivers/vfio/vfio_iommu_type1.c
> >> +++ b/drivers/vfio/vfio_iommu_type1.c
> >> @@ -71,6 +71,7 @@ struct vfio_iommu {
> >>   	unsigned int		dma_avail;
> >>   	bool			v2;
> >>   	bool			nesting;
> >> +	bool			dirty_page_tracking;
> >>   };
> >>   
> >>   struct vfio_domain {
> >> @@ -91,6 +92,7 @@ struct vfio_dma {
> >>   	bool			lock_cap;	/* capable(CAP_IPC_LOCK) */
> >>   	struct task_struct	*task;
> >>   	struct rb_root		pfn_list;	/* Ex-user pinned pfn list */
> >> +	unsigned long		*bitmap;
> >>   };
> >>   
> >>   struct vfio_group {
> >> @@ -125,7 +127,21 @@ struct vfio_regions {
> >>   #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
> >>   					(!list_empty(&iommu->domain_list))
> >>   
> >> +#define DIRTY_BITMAP_BYTES(n)	(ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE)
> >> +
> >> +/*
> >> + * Input argument of number of bits to bitmap_set() is unsigned integer, which
> >> + * further casts to signed integer for unaligned multi-bit operation,
> >> + * __bitmap_set().
> >> + * Then maximum bitmap size supported is 2^31 bits divided by 2^3 bits/byte,
> >> + * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page
> >> + * system.
> >> + */
> >> +#define DIRTY_BITMAP_PAGES_MAX	((1UL << 31) - 1)
> >> +#define DIRTY_BITMAP_SIZE_MAX	 DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
> >> +
> >>   static int put_pfn(unsigned long pfn, int prot);
> >> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
> >>   
> >>   /*
> >>    * This code handles mapping and unmapping of user data buffers
> >> @@ -175,6 +191,67 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
> >>   	rb_erase(&old->node, &iommu->dma_list);
> >>   }
> >>   
> >> +
> >> +static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, uint64_t pgsize)
> >> +{
> >> +	uint64_t npages = dma->size / pgsize;
> >> +  
> > 
> > Shouldn't we test this against one of the MAX macros defined above?  It
> > would be bad if we could enabled dirty tracking but not allow the user
> > to retrieve it.
> >   
> 
> Yes, adding check as below:
> 
>          if (npages > DIRTY_BITMAP_PAGES_MAX)
>                  -EINVAL;
> 
> 
> >> +	dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL);
> >> +	if (!dma->bitmap)
> >> +		return -ENOMEM;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, uint64_t pgsize)
> >> +{
> >> +	struct rb_node *n = rb_first(&iommu->dma_list);
> >> +
> >> +	for (; n; n = rb_next(n)) {
> >> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> >> +		struct rb_node *p;
> >> +		int ret;
> >> +
> >> +		ret = vfio_dma_bitmap_alloc(dma, pgsize);
> >> +		if (ret) {
> >> +			struct rb_node *p = rb_prev(n);
> >> +
> >> +			for (; p; p = rb_prev(p)) {
> >> +				struct vfio_dma *dma = rb_entry(n,
> >> +							struct vfio_dma, node);
> >> +
> >> +				kfree(dma->bitmap);
> >> +				dma->bitmap = NULL;
> >> +			}
> >> +			return ret;
> >> +		}
> >> +
> >> +		if (RB_EMPTY_ROOT(&dma->pfn_list))
> >> +			continue;
> >> +
> >> +		for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) {
> >> +			struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn,
> >> +							 node);
> >> +
> >> +			bitmap_set(dma->bitmap,
> >> +				   (vpfn->iova - dma->iova) / pgsize, 1);
> >> +		}
> >> +	}
> >> +	return 0;
> >> +}
> >> +
> >> +static void vfio_dma_bitmap_free_all(struct vfio_iommu *iommu)
> >> +{
> >> +	struct rb_node *n = rb_first(&iommu->dma_list);
> >> +
> >> +	for (; n; n = rb_next(n)) {
> >> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> >> +
> >> +		kfree(dma->bitmap);
> >> +		dma->bitmap = NULL;  
> > 
> > Might be useful to have a vfio_dma_bitmap_free() for here and above.
> >   
> 
> Ok.
> 
> >> +	}
> >> +}
> >> +
> >>   /*
> >>    * Helper Functions for host iova-pfn list
> >>    */
> >> @@ -567,6 +644,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
> >>   			vfio_unpin_page_external(dma, iova, do_accounting);
> >>   			goto pin_unwind;
> >>   		}
> >> +
> >> +		if (iommu->dirty_page_tracking) {
> >> +			unsigned long pgshift =
> >> +					 __ffs(vfio_pgsize_bitmap(iommu));
> >> +
> >> +			bitmap_set(dma->bitmap,
> >> +				   (vpfn->iova - dma->iova) >> pgshift, 1);
> >> +		}
> >>   	}
> >>   
> >>   	ret = i;
> >> @@ -801,6 +886,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
> >>   	vfio_unmap_unpin(iommu, dma, true);
> >>   	vfio_unlink_dma(iommu, dma);
> >>   	put_task_struct(dma->task);
> >> +	kfree(dma->bitmap);
> >>   	kfree(dma);
> >>   	iommu->dma_avail++;
> >>   }
> >> @@ -831,6 +917,50 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
> >>   	return bitmap;
> >>   }
> >>   
> >> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> >> +				  size_t size, uint64_t pgsize,
> >> +				  u64 __user *bitmap)
> >> +{
> >> +	struct vfio_dma *dma;
> >> +	unsigned long pgshift = __ffs(pgsize);
> >> +	unsigned int npages, bitmap_size;
> >> +
> >> +	dma = vfio_find_dma(iommu, iova, 1);
> >> +
> >> +	if (!dma)
> >> +		return -EINVAL;
> >> +
> >> +	if (dma->iova != iova || dma->size != size)
> >> +		return -EINVAL;
> >> +
> >> +	npages = dma->size >> pgshift;
> >> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> >> +
> >> +	/* mark all pages dirty if all pages are pinned and mapped. */
> >> +	if (dma->iommu_mapped)
> >> +		bitmap_set(dma->bitmap, 0, npages);
> >> +
> >> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> >> +		return -EFAULT;  
> > 
> > We still need to reset the bitmap here, clearing and re-adding the
> > pages that are still pinned.
> > 
> > https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> >   
> 
> I thought you agreed on my reply to it
> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> 
>  > Why re-populate when there will be no change since
>  > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
>  > pin request while vfio_iova_dirty_bitmap() is still working, it will
>  > wait till iommu->lock is released. Bitmap will be populated when page is
>  > pinned.  

As coded, dirty bits are only ever set in the bitmap, never cleared.
If a page is unpinned between iterations of the user recording the
dirty bitmap, it should be marked dirty in the iteration immediately
after the unpinning and not marked dirty in the following iteration.
That doesn't happen here.  We're reporting cumulative dirty pages since
logging was enabled, we need to be reporting dirty pages since the user
last retrieved the dirty bitmap.  The bitmap should be cleared and
currently pinned pages re-added after copying to the user.  Thanks,

Alex

> >> +	return 0;
> >> +}
> >> +
> >> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> >> +{
> >> +	uint64_t bsize;
> >> +
> >> +	if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_MAX))
> >> +		return -EINVAL;
> >> +
> >> +	bsize = DIRTY_BITMAP_BYTES(npages);
> >> +
> >> +	if (bitmap_size < bsize)
> >> +		return -EINVAL;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >>   static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> >>   			     struct vfio_iommu_type1_dma_unmap *unmap)
> >>   {
> >> @@ -1038,16 +1168,16 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> >>   	unsigned long vaddr = map->vaddr;
> >>   	size_t size = map->size;
> >>   	int ret = 0, prot = 0;
> >> -	uint64_t mask;
> >> +	uint64_t pgsize;
> >>   	struct vfio_dma *dma;
> >>   
> >>   	/* Verify that none of our __u64 fields overflow */
> >>   	if (map->size != size || map->vaddr != vaddr || map->iova != iova)
> >>   		return -EINVAL;
> >>   
> >> -	mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> >> +	pgsize = (uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu));
> >>   
> >> -	WARN_ON(mask & PAGE_MASK);
> >> +	WARN_ON((pgsize - 1) & PAGE_MASK);
> >>   
> >>   	/* READ/WRITE from device perspective */
> >>   	if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
> >> @@ -1055,7 +1185,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> >>   	if (map->flags & VFIO_DMA_MAP_FLAG_READ)
> >>   		prot |= IOMMU_READ;
> >>   
> >> -	if (!prot || !size || (size | iova | vaddr) & mask)
> >> +	if (!prot || !size || (size | iova | vaddr) & (pgsize - 1))
> >>   		return -EINVAL;
> >>   
> >>   	/* Don't allow IOVA or virtual address wrap */
> >> @@ -1130,6 +1260,12 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> >>   	else
> >>   		ret = vfio_pin_map_dma(iommu, dma, size);
> >>   
> >> +	if (!ret && iommu->dirty_page_tracking) {
> >> +		ret = vfio_dma_bitmap_alloc(dma, pgsize);
> >> +		if (ret)
> >> +			vfio_remove_dma(iommu, dma);
> >> +	}
> >> +
> >>   out_unlock:
> >>   	mutex_unlock(&iommu->lock);
> >>   	return ret;
> >> @@ -2278,6 +2414,93 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
> >>   
> >>   		return copy_to_user((void __user *)arg, &unmap, minsz) ?
> >>   			-EFAULT : 0;
> >> +	} else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
> >> +		struct vfio_iommu_type1_dirty_bitmap dirty;
> >> +		uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
> >> +				VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP |
> >> +				VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
> >> +		int ret = 0;
> >> +
> >> +		if (!iommu->v2)
> >> +			return -EACCES;
> >> +
> >> +		minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap,
> >> +				    flags);
> >> +
> >> +		if (copy_from_user(&dirty, (void __user *)arg, minsz))
> >> +			return -EFAULT;
> >> +
> >> +		if (dirty.argsz < minsz || dirty.flags & ~mask)
> >> +			return -EINVAL;
> >> +
> >> +		/* only one flag should be set at a time */
> >> +		if (__ffs(dirty.flags) != __fls(dirty.flags))
> >> +			return -EINVAL;
> >> +
> >> +		if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> >> +			uint64_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu));
> >> +
> >> +			mutex_lock(&iommu->lock);
> >> +			if (!iommu->dirty_page_tracking) {
> >> +				ret = vfio_dma_bitmap_alloc_all(iommu, pgsize);
> >> +				if (!ret)
> >> +					iommu->dirty_page_tracking = true;
> >> +			}
> >> +			mutex_unlock(&iommu->lock);
> >> +			return ret;
> >> +		} else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
> >> +			mutex_lock(&iommu->lock);
> >> +			if (iommu->dirty_page_tracking) {
> >> +				iommu->dirty_page_tracking = false;
> >> +				vfio_dma_bitmap_free_all(iommu);
> >> +			}
> >> +			mutex_unlock(&iommu->lock);
> >> +			return 0;
> >> +		} else if (dirty.flags &
> >> +				 VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
> >> +			struct vfio_iommu_type1_dirty_bitmap_get range;
> >> +			unsigned long pgshift;
> >> +			size_t data_size = dirty.argsz - minsz;
> >> +			uint64_t iommu_pgsize =
> >> +					 1 << __ffs(vfio_pgsize_bitmap(iommu));
> >> +
> >> +			if (!data_size || data_size < sizeof(range))
> >> +				return -EINVAL;
> >> +
> >> +			if (copy_from_user(&range, (void __user *)(arg + minsz),
> >> +					   sizeof(range)))
> >> +				return -EFAULT;
> >> +
> >> +			/* allow only min supported pgsize */
> >> +			if (range.bitmap.pgsize != iommu_pgsize)
> >> +				return -EINVAL;
> >> +			if (range.iova & (iommu_pgsize - 1))
> >> +				return -EINVAL;
> >> +			if (!range.size || range.size & (iommu_pgsize - 1))
> >> +				return -EINVAL;
> >> +			if (range.iova + range.size < range.iova)
> >> +				return -EINVAL;
> >> +			if (!access_ok((void __user *)range.bitmap.data,
> >> +				       range.bitmap.size))
> >> +				return -EINVAL;
> >> +
> >> +			pgshift = __ffs(range.bitmap.pgsize);
> >> +			ret = verify_bitmap_size(range.size >> pgshift,
> >> +						 range.bitmap.size);
> >> +			if (ret)
> >> +				return ret;
> >> +
> >> +			mutex_lock(&iommu->lock);
> >> +			if (iommu->dirty_page_tracking)
> >> +				ret = vfio_iova_dirty_bitmap(iommu, range.iova,
> >> +						range.size, range.bitmap.pgsize,
> >> +						range.bitmap.data);
> >> +			else
> >> +				ret = -EINVAL;
> >> +			mutex_unlock(&iommu->lock);
> >> +
> >> +			return ret;
> >> +		}
> >>   	}
> >>   
> >>   	return -ENOTTY;
> >> @@ -2345,10 +2568,17 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
> >>   
> >>   	vaddr = dma->vaddr + offset;
> >>   
> >> -	if (write)
> >> +	if (write) {
> >>   		*copied = __copy_to_user((void __user *)vaddr, data,
> >>   					 count) ? 0 : count;
> >> -	else
> >> +		if (*copied && iommu->dirty_page_tracking) {
> >> +			unsigned long pgshift =
> >> +				__ffs(vfio_pgsize_bitmap(iommu));
> >> +
> >> +			bitmap_set(dma->bitmap, offset >> pgshift,
> >> +				   *copied >> pgshift);
> >> +		}
> >> +	} else
> >>   		*copied = __copy_from_user(data, (void __user *)vaddr,
> >>   					   count) ? 0 : count;
> >>   	if (kthread)  
> >   
> 



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-20 18:01       ` Alex Williamson
@ 2020-03-20 18:42         ` Kirti Wankhede
  2020-03-20 18:59           ` Alex Williamson
  0 siblings, 1 reply; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-20 18:42 UTC (permalink / raw)
  To: Alex Williamson
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue



On 3/20/2020 11:31 PM, Alex Williamson wrote:
> On Fri, 20 Mar 2020 23:19:14 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> On 3/20/2020 4:27 AM, Alex Williamson wrote:
>>> On Fri, 20 Mar 2020 01:46:41 +0530
>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>    

<snip>

>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
>>>> +				  size_t size, uint64_t pgsize,
>>>> +				  u64 __user *bitmap)
>>>> +{
>>>> +	struct vfio_dma *dma;
>>>> +	unsigned long pgshift = __ffs(pgsize);
>>>> +	unsigned int npages, bitmap_size;
>>>> +
>>>> +	dma = vfio_find_dma(iommu, iova, 1);
>>>> +
>>>> +	if (!dma)
>>>> +		return -EINVAL;
>>>> +
>>>> +	if (dma->iova != iova || dma->size != size)
>>>> +		return -EINVAL;
>>>> +
>>>> +	npages = dma->size >> pgshift;
>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
>>>> +
>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
>>>> +	if (dma->iommu_mapped)
>>>> +		bitmap_set(dma->bitmap, 0, npages);
>>>> +
>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
>>>> +		return -EFAULT;
>>>
>>> We still need to reset the bitmap here, clearing and re-adding the
>>> pages that are still pinned.
>>>
>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
>>>    
>>
>> I thought you agreed on my reply to it
>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
>>
>>   > Why re-populate when there will be no change since
>>   > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
>>   > pin request while vfio_iova_dirty_bitmap() is still working, it will
>>   > wait till iommu->lock is released. Bitmap will be populated when page is
>>   > pinned.
> 
> As coded, dirty bits are only ever set in the bitmap, never cleared.
> If a page is unpinned between iterations of the user recording the
> dirty bitmap, it should be marked dirty in the iteration immediately
> after the unpinning and not marked dirty in the following iteration.
> That doesn't happen here.  We're reporting cumulative dirty pages since
> logging was enabled, we need to be reporting dirty pages since the user
> last retrieved the dirty bitmap.  The bitmap should be cleared and
> currently pinned pages re-added after copying to the user.  Thanks,
> 

Does that mean, we have to track every iteration? do we really need that 
tracking?

Generally the flow is:
- vendor driver pin x pages
- Enter pre-copy-phase where vCPUs are running - user starts dirty pages 
tracking, then user asks dirty bitmap, x pages reported dirty by 
VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
- In pre-copy phase, vendor driver pins y more pages, now bitmap 
consists of x+y bits set
- In pre-copy phase, vendor driver unpins z pages, but bitmap is not 
updated, so again bitmap consists of x+y bits set.
- Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
- user asks dirty bitmap - Since here vCPU and mdev devices are stopped, 
pages should not get dirty by guest driver or the physical device. 
Hence, x+y dirty pages would be reported.

I don't think we need to track every iteration of bitmap reporting.

Thanks,
Kirti





^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-20 18:42         ` Kirti Wankhede
@ 2020-03-20 18:59           ` Alex Williamson
  2020-03-23 17:54             ` Kirti Wankhede
  0 siblings, 1 reply; 29+ messages in thread
From: Alex Williamson @ 2020-03-20 18:59 UTC (permalink / raw)
  To: Kirti Wankhede
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue

On Sat, 21 Mar 2020 00:12:04 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 3/20/2020 11:31 PM, Alex Williamson wrote:
> > On Fri, 20 Mar 2020 23:19:14 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> On 3/20/2020 4:27 AM, Alex Williamson wrote:  
> >>> On Fri, 20 Mar 2020 01:46:41 +0530
> >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >>>      
> 
> <snip>
> 
> >>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> >>>> +				  size_t size, uint64_t pgsize,
> >>>> +				  u64 __user *bitmap)
> >>>> +{
> >>>> +	struct vfio_dma *dma;
> >>>> +	unsigned long pgshift = __ffs(pgsize);
> >>>> +	unsigned int npages, bitmap_size;
> >>>> +
> >>>> +	dma = vfio_find_dma(iommu, iova, 1);
> >>>> +
> >>>> +	if (!dma)
> >>>> +		return -EINVAL;
> >>>> +
> >>>> +	if (dma->iova != iova || dma->size != size)
> >>>> +		return -EINVAL;
> >>>> +
> >>>> +	npages = dma->size >> pgshift;
> >>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> >>>> +
> >>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
> >>>> +	if (dma->iommu_mapped)
> >>>> +		bitmap_set(dma->bitmap, 0, npages);
> >>>> +
> >>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> >>>> +		return -EFAULT;  
> >>>
> >>> We still need to reset the bitmap here, clearing and re-adding the
> >>> pages that are still pinned.
> >>>
> >>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> >>>      
> >>
> >> I thought you agreed on my reply to it
> >> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> >>  
> >>   > Why re-populate when there will be no change since
> >>   > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
> >>   > pin request while vfio_iova_dirty_bitmap() is still working, it will
> >>   > wait till iommu->lock is released. Bitmap will be populated when page is
> >>   > pinned.  
> > 
> > As coded, dirty bits are only ever set in the bitmap, never cleared.
> > If a page is unpinned between iterations of the user recording the
> > dirty bitmap, it should be marked dirty in the iteration immediately
> > after the unpinning and not marked dirty in the following iteration.
> > That doesn't happen here.  We're reporting cumulative dirty pages since
> > logging was enabled, we need to be reporting dirty pages since the user
> > last retrieved the dirty bitmap.  The bitmap should be cleared and
> > currently pinned pages re-added after copying to the user.  Thanks,
> >   
> 
> Does that mean, we have to track every iteration? do we really need that 
> tracking?
> 
> Generally the flow is:
> - vendor driver pin x pages
> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages 
> tracking, then user asks dirty bitmap, x pages reported dirty by 
> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> - In pre-copy phase, vendor driver pins y more pages, now bitmap 
> consists of x+y bits set
> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not 
> updated, so again bitmap consists of x+y bits set.
> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped, 
> pages should not get dirty by guest driver or the physical device. 
> Hence, x+y dirty pages would be reported.
> 
> I don't think we need to track every iteration of bitmap reporting.

Yes, once a bitmap is read, it's reset.  In your example, after
unpinning z pages the user should still see a bitmap with x+y pages,
but once they've read that bitmap, the next bitmap should be x+y-z.
Userspace can make decisions about when to switch from pre-copy to
stop-and-copy based on convergence, ie. the slope of the line recording
dirty pages per iteration.  The implementation here never allows an
inflection point, dirty pages reported through vfio would always either
be flat or climbing.  There might also be a case that an iommu backed
device could start pinning pages during the course of a migration, how
would the bitmap ever revert from fully populated to only tracking the
pinned pages?  Thanks,

Alex



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-20 18:59           ` Alex Williamson
@ 2020-03-23 17:54             ` Kirti Wankhede
  2020-03-23 18:44               ` Alex Williamson
  0 siblings, 1 reply; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-23 17:54 UTC (permalink / raw)
  To: Alex Williamson
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue



On 3/21/2020 12:29 AM, Alex Williamson wrote:
> On Sat, 21 Mar 2020 00:12:04 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> On 3/20/2020 11:31 PM, Alex Williamson wrote:
>>> On Fri, 20 Mar 2020 23:19:14 +0530
>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>    
>>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:
>>>>> On Fri, 20 Mar 2020 01:46:41 +0530
>>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>>>       
>>
>> <snip>
>>
>>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
>>>>>> +				  size_t size, uint64_t pgsize,
>>>>>> +				  u64 __user *bitmap)
>>>>>> +{
>>>>>> +	struct vfio_dma *dma;
>>>>>> +	unsigned long pgshift = __ffs(pgsize);
>>>>>> +	unsigned int npages, bitmap_size;
>>>>>> +
>>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
>>>>>> +
>>>>>> +	if (!dma)
>>>>>> +		return -EINVAL;
>>>>>> +
>>>>>> +	if (dma->iova != iova || dma->size != size)
>>>>>> +		return -EINVAL;
>>>>>> +
>>>>>> +	npages = dma->size >> pgshift;
>>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
>>>>>> +
>>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
>>>>>> +	if (dma->iommu_mapped)
>>>>>> +		bitmap_set(dma->bitmap, 0, npages);
>>>>>> +
>>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
>>>>>> +		return -EFAULT;
>>>>>
>>>>> We still need to reset the bitmap here, clearing and re-adding the
>>>>> pages that are still pinned.
>>>>>
>>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
>>>>>       
>>>>
>>>> I thought you agreed on my reply to it
>>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
>>>>   
>>>>    > Why re-populate when there will be no change since
>>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
>>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it will
>>>>    > wait till iommu->lock is released. Bitmap will be populated when page is
>>>>    > pinned.
>>>
>>> As coded, dirty bits are only ever set in the bitmap, never cleared.
>>> If a page is unpinned between iterations of the user recording the
>>> dirty bitmap, it should be marked dirty in the iteration immediately
>>> after the unpinning and not marked dirty in the following iteration.
>>> That doesn't happen here.  We're reporting cumulative dirty pages since
>>> logging was enabled, we need to be reporting dirty pages since the user
>>> last retrieved the dirty bitmap.  The bitmap should be cleared and
>>> currently pinned pages re-added after copying to the user.  Thanks,
>>>    
>>
>> Does that mean, we have to track every iteration? do we really need that
>> tracking?
>>
>> Generally the flow is:
>> - vendor driver pin x pages
>> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
>> tracking, then user asks dirty bitmap, x pages reported dirty by
>> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
>> - In pre-copy phase, vendor driver pins y more pages, now bitmap
>> consists of x+y bits set
>> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
>> updated, so again bitmap consists of x+y bits set.
>> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
>> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
>> pages should not get dirty by guest driver or the physical device.
>> Hence, x+y dirty pages would be reported.
>>
>> I don't think we need to track every iteration of bitmap reporting.
> 
> Yes, once a bitmap is read, it's reset.  In your example, after
> unpinning z pages the user should still see a bitmap with x+y pages,
> but once they've read that bitmap, the next bitmap should be x+y-z.
> Userspace can make decisions about when to switch from pre-copy to
> stop-and-copy based on convergence, ie. the slope of the line recording
> dirty pages per iteration.  The implementation here never allows an
> inflection point, dirty pages reported through vfio would always either
> be flat or climbing.  There might also be a case that an iommu backed
> device could start pinning pages during the course of a migration, how
> would the bitmap ever revert from fully populated to only tracking the
> pinned pages?  Thanks,
> 

At KVM forum we discussed this - if guest driver pins say 1024 pages 
before migration starts, during pre-copy phase device can dirty 0 pages 
in best case and 1024 pages in worst case. In that case, user will 
transfer content of 1024 pages during pre-copy phase and in 
stop-and-copy phase also, that will be pages will be copied twice. So we 
decided to only get dirty pages bitmap at stop-and-copy phase. If user 
is going to get dirty pages in stop-and-copy phase only, then that will 
be single iteration.
There aren't any devices yet that can track sys memory dirty pages. So 
we can go ahead with this patch and support for dirty pages tracking 
during pre-copy phase can be added later when there will be consumers of 
that functionality.

Thanks,
Kirti


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-23 17:54             ` Kirti Wankhede
@ 2020-03-23 18:44               ` Alex Williamson
  2020-03-23 18:51                 ` Dr. David Alan Gilbert
  0 siblings, 1 reply; 29+ messages in thread
From: Alex Williamson @ 2020-03-23 18:44 UTC (permalink / raw)
  To: Kirti Wankhede
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue

On Mon, 23 Mar 2020 23:24:37 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 3/21/2020 12:29 AM, Alex Williamson wrote:
> > On Sat, 21 Mar 2020 00:12:04 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> On 3/20/2020 11:31 PM, Alex Williamson wrote:  
> >>> On Fri, 20 Mar 2020 23:19:14 +0530
> >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >>>      
> >>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:  
> >>>>> On Fri, 20 Mar 2020 01:46:41 +0530
> >>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >>>>>         
> >>
> >> <snip>
> >>  
> >>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> >>>>>> +				  size_t size, uint64_t pgsize,
> >>>>>> +				  u64 __user *bitmap)
> >>>>>> +{
> >>>>>> +	struct vfio_dma *dma;
> >>>>>> +	unsigned long pgshift = __ffs(pgsize);
> >>>>>> +	unsigned int npages, bitmap_size;
> >>>>>> +
> >>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
> >>>>>> +
> >>>>>> +	if (!dma)
> >>>>>> +		return -EINVAL;
> >>>>>> +
> >>>>>> +	if (dma->iova != iova || dma->size != size)
> >>>>>> +		return -EINVAL;
> >>>>>> +
> >>>>>> +	npages = dma->size >> pgshift;
> >>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> >>>>>> +
> >>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
> >>>>>> +	if (dma->iommu_mapped)
> >>>>>> +		bitmap_set(dma->bitmap, 0, npages);
> >>>>>> +
> >>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> >>>>>> +		return -EFAULT;  
> >>>>>
> >>>>> We still need to reset the bitmap here, clearing and re-adding the
> >>>>> pages that are still pinned.
> >>>>>
> >>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> >>>>>         
> >>>>
> >>>> I thought you agreed on my reply to it
> >>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> >>>>     
> >>>>    > Why re-populate when there will be no change since
> >>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
> >>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it will
> >>>>    > wait till iommu->lock is released. Bitmap will be populated when page is
> >>>>    > pinned.  
> >>>
> >>> As coded, dirty bits are only ever set in the bitmap, never cleared.
> >>> If a page is unpinned between iterations of the user recording the
> >>> dirty bitmap, it should be marked dirty in the iteration immediately
> >>> after the unpinning and not marked dirty in the following iteration.
> >>> That doesn't happen here.  We're reporting cumulative dirty pages since
> >>> logging was enabled, we need to be reporting dirty pages since the user
> >>> last retrieved the dirty bitmap.  The bitmap should be cleared and
> >>> currently pinned pages re-added after copying to the user.  Thanks,
> >>>      
> >>
> >> Does that mean, we have to track every iteration? do we really need that
> >> tracking?
> >>
> >> Generally the flow is:
> >> - vendor driver pin x pages
> >> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
> >> tracking, then user asks dirty bitmap, x pages reported dirty by
> >> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> >> - In pre-copy phase, vendor driver pins y more pages, now bitmap
> >> consists of x+y bits set
> >> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
> >> updated, so again bitmap consists of x+y bits set.
> >> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
> >> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
> >> pages should not get dirty by guest driver or the physical device.
> >> Hence, x+y dirty pages would be reported.
> >>
> >> I don't think we need to track every iteration of bitmap reporting.  
> > 
> > Yes, once a bitmap is read, it's reset.  In your example, after
> > unpinning z pages the user should still see a bitmap with x+y pages,
> > but once they've read that bitmap, the next bitmap should be x+y-z.
> > Userspace can make decisions about when to switch from pre-copy to
> > stop-and-copy based on convergence, ie. the slope of the line recording
> > dirty pages per iteration.  The implementation here never allows an
> > inflection point, dirty pages reported through vfio would always either
> > be flat or climbing.  There might also be a case that an iommu backed
> > device could start pinning pages during the course of a migration, how
> > would the bitmap ever revert from fully populated to only tracking the
> > pinned pages?  Thanks,
> >   
> 
> At KVM forum we discussed this - if guest driver pins say 1024 pages 
> before migration starts, during pre-copy phase device can dirty 0 pages 
> in best case and 1024 pages in worst case. In that case, user will 
> transfer content of 1024 pages during pre-copy phase and in 
> stop-and-copy phase also, that will be pages will be copied twice. So we 
> decided to only get dirty pages bitmap at stop-and-copy phase. If user 
> is going to get dirty pages in stop-and-copy phase only, then that will 
> be single iteration.
> There aren't any devices yet that can track sys memory dirty pages. So 
> we can go ahead with this patch and support for dirty pages tracking 
> during pre-copy phase can be added later when there will be consumers of 
> that functionality.

So if I understand this right, you're expecting the dirty bitmap to
accumulate dirty bits, in perpetuity, so that the user can only
retrieve them once at the end of migration?  But if that's the case,
the user could simply choose to not retrieve the bitmap until the end
of migration, the result would be the same.  What we have here is that
dirty bits are never cleared, regardless of whether the user has seen
them, which is wrong.  Sorry, we had a lot of discussions at KVM forum,
I don't recall this specific one 5 months later and maybe we weren't
considering all aspects.  I see the behavior we have here as incorrect,
but it also seems relatively trivial to make correct.  I hope the QEMU
code isn't making us go through all this trouble to report a dirty
bitmap that gets thrown away because it expects the final one to be
cumulative since the beginning of dirty logging.  Thanks,

Alex



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-23 18:44               ` Alex Williamson
@ 2020-03-23 18:51                 ` Dr. David Alan Gilbert
  2020-03-24  3:01                   ` Yan Zhao
  0 siblings, 1 reply; 29+ messages in thread
From: Dr. David Alan Gilbert @ 2020-03-23 18:51 UTC (permalink / raw)
  To: Alex Williamson
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, cjia, kvm, eskultet,
	ziye.yang, cohuck, shuangtai.tst, qemu-devel, zhi.a.wang,
	mlevitsk, pasic, aik, Kirti Wankhede, eauger, felipe,
	jonathan.davies, yan.y.zhao, changpeng.liu, Ken.Xue

* Alex Williamson (alex.williamson@redhat.com) wrote:
> On Mon, 23 Mar 2020 23:24:37 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
> > On 3/21/2020 12:29 AM, Alex Williamson wrote:
> > > On Sat, 21 Mar 2020 00:12:04 +0530
> > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > >   
> > >> On 3/20/2020 11:31 PM, Alex Williamson wrote:  
> > >>> On Fri, 20 Mar 2020 23:19:14 +0530
> > >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > >>>      
> > >>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:  
> > >>>>> On Fri, 20 Mar 2020 01:46:41 +0530
> > >>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > >>>>>         
> > >>
> > >> <snip>
> > >>  
> > >>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> > >>>>>> +				  size_t size, uint64_t pgsize,
> > >>>>>> +				  u64 __user *bitmap)
> > >>>>>> +{
> > >>>>>> +	struct vfio_dma *dma;
> > >>>>>> +	unsigned long pgshift = __ffs(pgsize);
> > >>>>>> +	unsigned int npages, bitmap_size;
> > >>>>>> +
> > >>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
> > >>>>>> +
> > >>>>>> +	if (!dma)
> > >>>>>> +		return -EINVAL;
> > >>>>>> +
> > >>>>>> +	if (dma->iova != iova || dma->size != size)
> > >>>>>> +		return -EINVAL;
> > >>>>>> +
> > >>>>>> +	npages = dma->size >> pgshift;
> > >>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> > >>>>>> +
> > >>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
> > >>>>>> +	if (dma->iommu_mapped)
> > >>>>>> +		bitmap_set(dma->bitmap, 0, npages);
> > >>>>>> +
> > >>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> > >>>>>> +		return -EFAULT;  
> > >>>>>
> > >>>>> We still need to reset the bitmap here, clearing and re-adding the
> > >>>>> pages that are still pinned.
> > >>>>>
> > >>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> > >>>>>         
> > >>>>
> > >>>> I thought you agreed on my reply to it
> > >>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> > >>>>     
> > >>>>    > Why re-populate when there will be no change since
> > >>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
> > >>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it will
> > >>>>    > wait till iommu->lock is released. Bitmap will be populated when page is
> > >>>>    > pinned.  
> > >>>
> > >>> As coded, dirty bits are only ever set in the bitmap, never cleared.
> > >>> If a page is unpinned between iterations of the user recording the
> > >>> dirty bitmap, it should be marked dirty in the iteration immediately
> > >>> after the unpinning and not marked dirty in the following iteration.
> > >>> That doesn't happen here.  We're reporting cumulative dirty pages since
> > >>> logging was enabled, we need to be reporting dirty pages since the user
> > >>> last retrieved the dirty bitmap.  The bitmap should be cleared and
> > >>> currently pinned pages re-added after copying to the user.  Thanks,
> > >>>      
> > >>
> > >> Does that mean, we have to track every iteration? do we really need that
> > >> tracking?
> > >>
> > >> Generally the flow is:
> > >> - vendor driver pin x pages
> > >> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
> > >> tracking, then user asks dirty bitmap, x pages reported dirty by
> > >> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> > >> - In pre-copy phase, vendor driver pins y more pages, now bitmap
> > >> consists of x+y bits set
> > >> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
> > >> updated, so again bitmap consists of x+y bits set.
> > >> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
> > >> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
> > >> pages should not get dirty by guest driver or the physical device.
> > >> Hence, x+y dirty pages would be reported.
> > >>
> > >> I don't think we need to track every iteration of bitmap reporting.  
> > > 
> > > Yes, once a bitmap is read, it's reset.  In your example, after
> > > unpinning z pages the user should still see a bitmap with x+y pages,
> > > but once they've read that bitmap, the next bitmap should be x+y-z.
> > > Userspace can make decisions about when to switch from pre-copy to
> > > stop-and-copy based on convergence, ie. the slope of the line recording
> > > dirty pages per iteration.  The implementation here never allows an
> > > inflection point, dirty pages reported through vfio would always either
> > > be flat or climbing.  There might also be a case that an iommu backed
> > > device could start pinning pages during the course of a migration, how
> > > would the bitmap ever revert from fully populated to only tracking the
> > > pinned pages?  Thanks,
> > >   
> > 
> > At KVM forum we discussed this - if guest driver pins say 1024 pages 
> > before migration starts, during pre-copy phase device can dirty 0 pages 
> > in best case and 1024 pages in worst case. In that case, user will 
> > transfer content of 1024 pages during pre-copy phase and in 
> > stop-and-copy phase also, that will be pages will be copied twice. So we 
> > decided to only get dirty pages bitmap at stop-and-copy phase. If user 
> > is going to get dirty pages in stop-and-copy phase only, then that will 
> > be single iteration.
> > There aren't any devices yet that can track sys memory dirty pages. So 
> > we can go ahead with this patch and support for dirty pages tracking 
> > during pre-copy phase can be added later when there will be consumers of 
> > that functionality.
> 
> So if I understand this right, you're expecting the dirty bitmap to
> accumulate dirty bits, in perpetuity, so that the user can only
> retrieve them once at the end of migration?  But if that's the case,
> the user could simply choose to not retrieve the bitmap until the end
> of migration, the result would be the same.  What we have here is that
> dirty bits are never cleared, regardless of whether the user has seen
> them, which is wrong.  Sorry, we had a lot of discussions at KVM forum,
> I don't recall this specific one 5 months later and maybe we weren't
> considering all aspects.  I see the behavior we have here as incorrect,
> but it also seems relatively trivial to make correct.  I hope the QEMU
> code isn't making us go through all this trouble to report a dirty
> bitmap that gets thrown away because it expects the final one to be
> cumulative since the beginning of dirty logging.  Thanks,

I remember the discussion that we couldn't track the system memory
dirtying with current hardware; so the question then is just to track
what has been pinned and then ideally put that memory off until the end.
(Which is interesting because I don't think we currently have  a way
to delay RAM pages till the end in qemu).

[I still worry whether migration will be usable with any
significant amount of system ram that's pinned in this way; the
downside will very easily get above the threshold that people like]

Dave

> Alex
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state
  2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
@ 2020-03-23 20:30   ` Auger Eric
  2020-03-24 19:31     ` Kirti Wankhede
  2020-03-26  9:33   ` Christoph Hellwig
  1 sibling, 1 reply; 29+ messages in thread
From: Auger Eric @ 2020-03-23 20:30 UTC (permalink / raw)
  To: Kirti Wankhede, alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

Hi Kirti,

On 3/19/20 9:16 PM, Kirti Wankhede wrote:
> - Defined MIGRATION region type and sub-type.
> 
> - Defined vfio_device_migration_info structure which will be placed at the
>   0th offset of migration region to get/set VFIO device related
>   information. Defined members of structure and usage on read/write access.
> 
> - Defined device states and state transition details.
> 
> - Defined sequence to be followed while saving and resuming VFIO device.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>

Please forgive me, I have just discovered v15 was available.

hereafter, you will find the 2 main points I feel difficult to
understand when reading the documentation.

> ---
>  include/uapi/linux/vfio.h | 227 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 227 insertions(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 9e843a147ead..d0021467af53 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -305,6 +305,7 @@ struct vfio_region_info_cap_type {
>  #define VFIO_REGION_TYPE_PCI_VENDOR_MASK	(0xffff)
>  #define VFIO_REGION_TYPE_GFX                    (1)
>  #define VFIO_REGION_TYPE_CCW			(2)
> +#define VFIO_REGION_TYPE_MIGRATION              (3)
>  
>  /* sub-types for VFIO_REGION_TYPE_PCI_* */
>  
> @@ -379,6 +380,232 @@ struct vfio_region_gfx_edid {
>  /* sub-types for VFIO_REGION_TYPE_CCW */
>  #define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD	(1)
>  
> +/* sub-types for VFIO_REGION_TYPE_MIGRATION */
> +#define VFIO_REGION_SUBTYPE_MIGRATION           (1)
> +
> +/*
> + * The structure vfio_device_migration_info is placed at the 0th offset of
> + * the VFIO_REGION_SUBTYPE_MIGRATION region to get and set VFIO device related
> + * migration information. Field accesses from this structure are only supported
> + * at their native width and alignment. Otherwise, the result is undefined and
> + * vendor drivers should return an error.
> + *
> + * device_state: (read/write)
> + *      - The user application writes to this field to inform the vendor driver
> + *        about the device state to be transitioned to.
> + *      - The vendor driver should take the necessary actions to change the
> + *        device state. After successful transition to a given state, the
> + *        vendor driver should return success on write(device_state, state)
> + *        system call. If the device state transition fails, the vendor driver
> + *        should return an appropriate -errno for the fault condition.
> + *      - On the user application side, if the device state transition fails,
> + *	  that is, if write(device_state, state) returns an error, read
> + *	  device_state again to determine the current state of the device from
> + *	  the vendor driver.
> + *      - The vendor driver should return previous state of the device unless
> + *        the vendor driver has encountered an internal error, in which case
> + *        the vendor driver may report the device_state VFIO_DEVICE_STATE_ERROR.
> + *      - The user application must use the device reset ioctl to recover the
> + *        device from VFIO_DEVICE_STATE_ERROR state. If the device is
> + *        indicated to be in a valid device state by reading device_state, the
> + *        user application may attempt to transition the device to any valid
> + *        state reachable from the current state or terminate itself.
> + *
> + *      device_state consists of 3 bits:
> + *      - If bit 0 is set, it indicates the _RUNNING state. If bit 0 is clear,
> + *        it indicates the _STOP state. When the device state is changed to
> + *        _STOP, driver should stop the device before write() returns.
> + *      - If bit 1 is set, it indicates the _SAVING state, which means that the
> + *        driver should start gathering device state information that will be
> + *        provided to the VFIO user application to save the device's state.
> + *      - If bit 2 is set, it indicates the _RESUMING state, which means that
> + *        the driver should prepare to resume the device. Data provided through
> + *        the migration region should be used to resume the device.
> + *      Bits 3 - 31 are reserved for future use. To preserve them, the user
> + *      application should perform a read-modify-write operation on this
> + *      field when modifying the specified bits.
> + *
> + *  +------- _RESUMING
> + *  |+------ _SAVING
> + *  ||+----- _RUNNING
> + *  |||
> + *  000b => Device Stopped, not saving or resuming
> + *  001b => Device running, which is the default state
> + *  010b => Stop the device & save the device state, stop-and-copy state
> + *  011b => Device running and save the device state, pre-copy state
> + *  100b => Device stopped and the device state is resuming
> + *  101b => Invalid state
> + *  110b => Error state
> + *  111b => Invalid state
> + *
> + * State transitions:
> + *
> + *              _RESUMING  _RUNNING    Pre-copy    Stop-and-copy   _STOP
> + *                (100b)     (001b)     (011b)        (010b)       (000b)
> + * 0. Running or default state
> + *                             |
> + *
> + * 1. Normal Shutdown (optional)
> + *                             |------------------------------------->|
> + *
> + * 2. Save the state or suspend
> + *                             |------------------------->|---------->|
> + *
> + * 3. Save the state during live migration
> + *                             |----------->|------------>|---------->|
> + *
> + * 4. Resuming
> + *                  |<---------|
> + *
> + * 5. Resumed
> + *                  |--------->|
> + *
> + * 0. Default state of VFIO device is _RUNNNG when the user application starts.
> + * 1. During normal shutdown of the user application, the user application may
> + *    optionally change the VFIO device state from _RUNNING to _STOP. This
> + *    transition is optional. The vendor driver must support this transition but
> + *    must not require it.
> + * 2. When the user application saves state or suspends the application, the
> + *    device state transitions from _RUNNING to stop-and-copy and then to _STOP.
> + *    On state transition from _RUNNING to stop-and-copy, driver must stop the
> + *    device, save the device state and send it to the application through the
> + *    migration region. The sequence to be followed for such transition is given
> + *    below.
> + * 3. In live migration of user application, the state transitions from _RUNNING
> + *    to pre-copy, to stop-and-copy, and to _STOP.
> + *    On state transition from _RUNNING to pre-copy, the driver should start
> + *    gathering the device state while the application is still running and send
> + *    the device state data to application through the migration region.
> + *    On state transition from pre-copy to stop-and-copy, the driver must stop
> + *    the device, save the device state and send it to the user application
> + *    through the migration region.
> + *    Vendor drivers must support the pre-copy state even for implementations
> + *    where no data is provided to the user before the stop-and-copy state. The
> + *    user must not be required to consume all migration data before the device
> + *    transitions to a new state, including the stop-and-copy state.
> + *    The sequence to be followed for above two transitions is given below.
> + * 4. To start the resuming phase, the device state should be transitioned from
> + *    the _RUNNING to the _RESUMING state.
> + *    In the _RESUMING state, the driver should use the device state data
> + *    received through the migration region to resume the device.
> + * 5. After providing saved device data to the driver, the application should
> + *    change the state from _RESUMING to _RUNNING.
> + *
> + * reserved:
> + *      Reads on this field return zero and writes are ignored.
> + *
> + * pending_bytes: (read only)
> + *      The number of pending bytes still to be migrated from the vendor driver.
> + *
> + * data_offset: (read only)
> + *      The user application should read data_offset in the migration region
> + *      from where the user application should read the device data during the
> + *      _SAVING state or write the device data during the _RESUMING state. See
> + *      below for details of sequence to be followed.
> + *
> + * data_size: (read/write)
> + *      The user application should read data_size to get the size in bytes of
> + *      the data copied in the migration region during the _SAVING state and
> + *      write the size in bytes of the data copied in the migration region
> + *      during the _RESUMING state.
> + *
> + * The format of the migration region is as follows:
> + *  ------------------------------------------------------------------
> + * |vfio_device_migration_info|    data section                      |
> + * |                          |     ///////////////////////////////  |
> + * ------------------------------------------------------------------
> + *   ^                              ^
> + *  offset 0-trapped part        data_offset
> + *
> + * The structure vfio_device_migration_info is always followed by the data
> + * section in the region, so data_offset will always be nonzero. The offset
> + * from where the data is copied is decided by the kernel driver. The data
> + * section can be trapped, mapped, or partitioned, depending on how the kernel
> + * driver defines the data section. The data section partition can be defined
> + * as mapped by the sparse mmap capability. If mmapped, data_offset should be
> + * page aligned, whereas initial section which contains the
> + * vfio_device_migration_info structure, might not end at the offset, which is
> + * page aligned. The user is not required to access through mmap regardless
> + * of the capabilities of the region mmap.
> + * The vendor driver should determine whether and how to partition the data
> + * section. The vendor driver should return data_offset accordingly.
> + *
> + * The sequence to be followed for the _SAVING|_RUNNING device state or
> + * pre-copy phase and for the _SAVING device state or stop-and-copy phase is as
> + * follows:
> + * a. Read pending_bytes, indicating the start of a new iteration to get device
> + *    data. Repeated read on pending_bytes at this stage should have no side
> + *    effects.
> + *    If pending_bytes == 0, the user application should not iterate to get data
> + *    for that device.
I do not feel comfortable with the above sentence. In pre-save state,
the device is running and I understand nothing prevents from getting new
state data even after the pending_bytes reached 0.
> + *    If pending_bytes > 0, perform the following steps.
> + * b. Read data_offset, indicating that the vendor driver should make data
> + *    available through the data section. The vendor driver should return this
> + *    read operation only after data is available from (region + data_offset)
> + *    to (region + data_offset + data_size).
> + * c. Read data_size, which is the amount of data in bytes available through
> + *    the migration region.
> + *    Read on data_offset and data_size should return the offset and size of
> + *    the current buffer if the user application reads data_offset and
> + *    data_size more than once here.
> + * d. Read data_size bytes of data from (region + data_offset) from the
> + *    migration region.
> + * e. Process the data.
> + * f. Read pending_bytes, which indicates that the data from the previous
> + *    iteration has been read. If pending_bytes > 0, go to step b.
> + *
> + * If an error occurs during the above sequence, the vendor driver can return
> + * an error code for next read() or write() operation, which will terminate the
> + * loop. The user application should then take the next necessary action, for
> + * example, failing migration or terminating the user application.> + *
> + * The user application can transition from the _SAVING|_RUNNING
> + * (pre-copy state) to the _SAVING (stop-and-copy) state regardless of the
> + * number of pending bytes. The user application should iterate in _SAVING
> + * (stop-and-copy) until pending_bytes is 0.
> + *
> + * The sequence to be followed while _RESUMING device state is as follows:
> + * While data for this device is available, repeat the following steps:
> + * a. Read data_offset from where the user application should write data.
> + * b. Write migration data starting at the migration region + data_offset for
> + *    the length determined by data_size from the migration source.
> + * c. Write data_size, which indicates to the vendor driver that data is
> + *    written in the migration region. Vendor driver should apply the
> + *    user-provided migration region data to the device resume state.
This is not clear to me when the data gets consumed by the device. Is
the write data_size blocking? Is the data offset moving to make sure the
user data will not be overriden? Can the the userapp refill immediately?
At least some hints about possible implementation would ease the
understanding.

Thanks

Eric
> + *
> + * For the user application, data is opaque. The user application should write
> + * data in the same order as the data is received and the data should be of
> + * same transaction size at the source.
> + */
> +
> +struct vfio_device_migration_info {
> +	__u32 device_state;         /* VFIO device state */
> +#define VFIO_DEVICE_STATE_STOP      (0)
> +#define VFIO_DEVICE_STATE_RUNNING   (1 << 0)
> +#define VFIO_DEVICE_STATE_SAVING    (1 << 1)
> +#define VFIO_DEVICE_STATE_RESUMING  (1 << 2)
> +#define VFIO_DEVICE_STATE_MASK      (VFIO_DEVICE_STATE_RUNNING | \
> +				     VFIO_DEVICE_STATE_SAVING |  \
> +				     VFIO_DEVICE_STATE_RESUMING)
> +
> +#define VFIO_DEVICE_STATE_VALID(state) \
> +	(state & VFIO_DEVICE_STATE_RESUMING ? \
> +	(state & VFIO_DEVICE_STATE_MASK) == VFIO_DEVICE_STATE_RESUMING : 1)
> +
> +#define VFIO_DEVICE_STATE_IS_ERROR(state) \
> +	((state & VFIO_DEVICE_STATE_MASK) == (VFIO_DEVICE_STATE_SAVING | \
> +					      VFIO_DEVICE_STATE_RESUMING))
> +
> +#define VFIO_DEVICE_STATE_SET_ERROR(state) \
> +	((state & ~VFIO_DEVICE_STATE_MASK) | VFIO_DEVICE_SATE_SAVING | \
> +					     VFIO_DEVICE_STATE_RESUMING)
> +
> +	__u32 reserved;
> +	__u64 pending_bytes;
> +	__u64 data_offset;
> +	__u64 data_size;
> +} __attribute__((packed));
> +
>  /*
>   * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
>   * which allows direct access to non-MSIX registers which happened to be within
> 



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages
  2020-03-19 20:16 ` [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Kirti Wankhede
@ 2020-03-23 20:30   ` Auger Eric
  2020-03-24 19:34     ` Kirti Wankhede
  0 siblings, 1 reply; 29+ messages in thread
From: Auger Eric @ 2020-03-23 20:30 UTC (permalink / raw)
  To: Kirti Wankhede, alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

Hi Kirti,

On 3/19/20 9:16 PM, Kirti Wankhede wrote:
> vfio_pfn.ref_count is always updated by holding iommu->lock, using atomic
> variable is overkill.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  drivers/vfio/vfio_iommu_type1.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 9fdfae1cb17a..70aeab921d0f 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -112,7 +112,7 @@ struct vfio_pfn {
>  	struct rb_node		node;
>  	dma_addr_t		iova;		/* Device address */
>  	unsigned long		pfn;		/* Host pfn */
> -	atomic_t		ref_count;
> +	unsigned int		ref_count;
>  };
>  
>  struct vfio_regions {
> @@ -233,7 +233,7 @@ static int vfio_add_to_pfn_list(struct vfio_dma *dma, dma_addr_t iova,
>  
>  	vpfn->iova = iova;
>  	vpfn->pfn = pfn;
> -	atomic_set(&vpfn->ref_count, 1);
> +	vpfn->ref_count = 1;
>  	vfio_link_pfn(dma, vpfn);
>  	return 0;
>  }
> @@ -251,7 +251,7 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
>  	struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
>  
>  	if (vpfn)
> -		atomic_inc(&vpfn->ref_count);
> +		vpfn->ref_count++;
>  	return vpfn;
>  }
>  
> @@ -259,7 +259,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
>  {
>  	int ret = 0;
>  
> -	if (atomic_dec_and_test(&vpfn->ref_count)) {
> +	vpfn->ref_count--;
> +	if (!vpfn->ref_count) {
>  		ret = put_pfn(vpfn->pfn, dma->prot);
>  		vfio_remove_from_pfn_list(dma, vpfn);
>  	}
> 



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking.
  2020-03-19 20:16 ` [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
@ 2020-03-23 21:11   ` Auger Eric
  2020-03-24 19:49     ` Kirti Wankhede
  0 siblings, 1 reply; 29+ messages in thread
From: Auger Eric @ 2020-03-23 21:11 UTC (permalink / raw)
  To: Kirti Wankhede, alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue

Hi Kirti,

On 3/19/20 9:16 PM, Kirti Wankhede wrote:
> IOMMU container maintains a list of all pages pinned by vfio_pin_pages API.
> All pages pinned by vendor driver through this API should be considered as
> dirty during migration. When container consists of IOMMU capable device and
> all pages are pinned and mapped, then all pages are marked dirty.
> Added support to start/stop dirtied pages tracking and to get bitmap of all
> dirtied pages for requested IO virtual address range.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  include/uapi/linux/vfio.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index d0021467af53..8138f94cac15 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -995,6 +995,12 @@ struct vfio_iommu_type1_dma_map {
>  
>  #define VFIO_IOMMU_MAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 13)
>  
> +struct vfio_bitmap {
> +	__u64        pgsize;	/* page size for bitmap */
in bytes as well
> +	__u64        size;	/* in bytes */
> +	__u64 __user *data;	/* one bit per page */
> +};
> +
>  /**
>   * VFIO_IOMMU_UNMAP_DMA - _IOWR(VFIO_TYPE, VFIO_BASE + 14,
>   *							struct vfio_dma_unmap)
> @@ -1021,6 +1027,55 @@ struct vfio_iommu_type1_dma_unmap {
>  #define VFIO_IOMMU_ENABLE	_IO(VFIO_TYPE, VFIO_BASE + 15)
>  #define VFIO_IOMMU_DISABLE	_IO(VFIO_TYPE, VFIO_BASE + 16)
>  
> +/**
> + * VFIO_IOMMU_DIRTY_PAGES - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
> + *                                     struct vfio_iommu_type1_dirty_bitmap)
> + * IOCTL is used for dirty pages tracking. Caller sets argsz, which is size of> + * struct vfio_iommu_type1_dirty_bitmap.
nit: This may become outdated when adding new fields. argz use mode is
documented at the beginning of the file.

 Caller set flag depend on which
> + * operation to perform, details as below:
> + *
> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_START set, indicates
> + * migration is active and IOMMU module should track pages which are dirtied or
> + * potentially dirtied by device.
> + * Dirty pages are tracked until tracking is stopped by user application by
> + * setting VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP flag.
> + *
> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP set, indicates
> + * IOMMU should stop tracking dirtied pages.
> + *
> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP flag set,
> + * IOCTL returns dirty pages bitmap for IOMMU container during migration for
> + * given IOVA range. User must provide data[] as the structure
> + * vfio_iommu_type1_dirty_bitmap_get through which user provides IOVA range
I think the fact the IOVA range must match the vfio dma_size must be
documented.
 and
> + * pgsize. This interface supports to get bitmap of smallest supported pgsize
> + * only and can be modified in future to get bitmap of specified pgsize.
> + * User must allocate memory for bitmap, zero the bitmap memory and set size
> + * of allocated memory in bitmap_size field. One bit is used to represent one
> + * page consecutively starting from iova offset. User should provide page size
> + * in 'pgsize'. Bit set in bitmap indicates page at that offset from iova is
> + * dirty. Caller must set argsz including size of structure
> + * vfio_iommu_type1_dirty_bitmap_get.
nit: ditto
> + *
> + * Only one of the flags _START, STOP and _GET may be specified at a time.
> + *
> + */
> +struct vfio_iommu_type1_dirty_bitmap {
> +	__u32        argsz;
> +	__u32        flags;
> +#define VFIO_IOMMU_DIRTY_PAGES_FLAG_START	(1 << 0)
> +#define VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP	(1 << 1)
> +#define VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP	(1 << 2)
> +	__u8         data[];
> +};
> +
> +struct vfio_iommu_type1_dirty_bitmap_get {
> +	__u64              iova;	/* IO virtual address */
> +	__u64              size;	/* Size of iova range */
> +	struct vfio_bitmap bitmap;
> +};
> +
> +#define VFIO_IOMMU_DIRTY_PAGES             _IO(VFIO_TYPE, VFIO_BASE + 17)
> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>  
>  /*
> 
Thanks

Eric



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-23 18:51                 ` Dr. David Alan Gilbert
@ 2020-03-24  3:01                   ` Yan Zhao
  2020-03-24  9:45                     ` Kirti Wankhede
  2020-03-24 14:36                     ` Alex Williamson
  0 siblings, 2 replies; 29+ messages in thread
From: Yan Zhao @ 2020-03-24  3:01 UTC (permalink / raw)
  To: Dr. David Alan Gilbert
  Cc: Zhengxiao.zx, Tian, Kevin, Liu, Yi L, cjia, kvm, eskultet, Yang,
	Ziye, qemu-devel, cohuck, shuangtai.tst, Kirti Wankhede, Wang,
	Zhi A, mlevitsk, pasic, aik, Alex Williamson, eauger, felipe,
	jonathan.davies, Liu, Changpeng, Ken.Xue

On Tue, Mar 24, 2020 at 02:51:14AM +0800, Dr. David Alan Gilbert wrote:
> * Alex Williamson (alex.williamson@redhat.com) wrote:
> > On Mon, 23 Mar 2020 23:24:37 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > 
> > > On 3/21/2020 12:29 AM, Alex Williamson wrote:
> > > > On Sat, 21 Mar 2020 00:12:04 +0530
> > > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > >   
> > > >> On 3/20/2020 11:31 PM, Alex Williamson wrote:  
> > > >>> On Fri, 20 Mar 2020 23:19:14 +0530
> > > >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > >>>      
> > > >>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:  
> > > >>>>> On Fri, 20 Mar 2020 01:46:41 +0530
> > > >>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > >>>>>         
> > > >>
> > > >> <snip>
> > > >>  
> > > >>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> > > >>>>>> +				  size_t size, uint64_t pgsize,
> > > >>>>>> +				  u64 __user *bitmap)
> > > >>>>>> +{
> > > >>>>>> +	struct vfio_dma *dma;
> > > >>>>>> +	unsigned long pgshift = __ffs(pgsize);
> > > >>>>>> +	unsigned int npages, bitmap_size;
> > > >>>>>> +
> > > >>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
> > > >>>>>> +
> > > >>>>>> +	if (!dma)
> > > >>>>>> +		return -EINVAL;
> > > >>>>>> +
> > > >>>>>> +	if (dma->iova != iova || dma->size != size)
> > > >>>>>> +		return -EINVAL;
> > > >>>>>> +
> > > >>>>>> +	npages = dma->size >> pgshift;
> > > >>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> > > >>>>>> +
> > > >>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
> > > >>>>>> +	if (dma->iommu_mapped)
> > > >>>>>> +		bitmap_set(dma->bitmap, 0, npages);
> > > >>>>>> +
> > > >>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> > > >>>>>> +		return -EFAULT;  
> > > >>>>>
> > > >>>>> We still need to reset the bitmap here, clearing and re-adding the
> > > >>>>> pages that are still pinned.
> > > >>>>>
> > > >>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> > > >>>>>         
> > > >>>>
> > > >>>> I thought you agreed on my reply to it
> > > >>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> > > >>>>     
> > > >>>>    > Why re-populate when there will be no change since
> > > >>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
> > > >>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it will
> > > >>>>    > wait till iommu->lock is released. Bitmap will be populated when page is
> > > >>>>    > pinned.  
> > > >>>
> > > >>> As coded, dirty bits are only ever set in the bitmap, never cleared.
> > > >>> If a page is unpinned between iterations of the user recording the
> > > >>> dirty bitmap, it should be marked dirty in the iteration immediately
> > > >>> after the unpinning and not marked dirty in the following iteration.
> > > >>> That doesn't happen here.  We're reporting cumulative dirty pages since
> > > >>> logging was enabled, we need to be reporting dirty pages since the user
> > > >>> last retrieved the dirty bitmap.  The bitmap should be cleared and
> > > >>> currently pinned pages re-added after copying to the user.  Thanks,
> > > >>>      
> > > >>
> > > >> Does that mean, we have to track every iteration? do we really need that
> > > >> tracking?
> > > >>
> > > >> Generally the flow is:
> > > >> - vendor driver pin x pages
> > > >> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
> > > >> tracking, then user asks dirty bitmap, x pages reported dirty by
> > > >> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> > > >> - In pre-copy phase, vendor driver pins y more pages, now bitmap
> > > >> consists of x+y bits set
> > > >> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
> > > >> updated, so again bitmap consists of x+y bits set.
> > > >> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
> > > >> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
> > > >> pages should not get dirty by guest driver or the physical device.
> > > >> Hence, x+y dirty pages would be reported.
> > > >>
> > > >> I don't think we need to track every iteration of bitmap reporting.  
> > > > 
> > > > Yes, once a bitmap is read, it's reset.  In your example, after
> > > > unpinning z pages the user should still see a bitmap with x+y pages,
> > > > but once they've read that bitmap, the next bitmap should be x+y-z.
> > > > Userspace can make decisions about when to switch from pre-copy to
> > > > stop-and-copy based on convergence, ie. the slope of the line recording
> > > > dirty pages per iteration.  The implementation here never allows an
> > > > inflection point, dirty pages reported through vfio would always either
> > > > be flat or climbing.  There might also be a case that an iommu backed
> > > > device could start pinning pages during the course of a migration, how
> > > > would the bitmap ever revert from fully populated to only tracking the
> > > > pinned pages?  Thanks,
> > > >   
> > > 
> > > At KVM forum we discussed this - if guest driver pins say 1024 pages 
> > > before migration starts, during pre-copy phase device can dirty 0 pages 
> > > in best case and 1024 pages in worst case. In that case, user will 
> > > transfer content of 1024 pages during pre-copy phase and in 
> > > stop-and-copy phase also, that will be pages will be copied twice. So we 
> > > decided to only get dirty pages bitmap at stop-and-copy phase. If user 
> > > is going to get dirty pages in stop-and-copy phase only, then that will 
> > > be single iteration.
> > > There aren't any devices yet that can track sys memory dirty pages. So 
> > > we can go ahead with this patch and support for dirty pages tracking 
> > > during pre-copy phase can be added later when there will be consumers of 
> > > that functionality.
> > 
> > So if I understand this right, you're expecting the dirty bitmap to
> > accumulate dirty bits, in perpetuity, so that the user can only
> > retrieve them once at the end of migration?  But if that's the case,
> > the user could simply choose to not retrieve the bitmap until the end
> > of migration, the result would be the same.  What we have here is that
> > dirty bits are never cleared, regardless of whether the user has seen
> > them, which is wrong.  Sorry, we had a lot of discussions at KVM forum,
> > I don't recall this specific one 5 months later and maybe we weren't
> > considering all aspects.  I see the behavior we have here as incorrect,
> > but it also seems relatively trivial to make correct.  I hope the QEMU
> > code isn't making us go through all this trouble to report a dirty
> > bitmap that gets thrown away because it expects the final one to be
> > cumulative since the beginning of dirty logging.  Thanks,
> 
> I remember the discussion that we couldn't track the system memory
> dirtying with current hardware; so the question then is just to track
hi Dave
there are already devices that are able to track the system memory,
through two ways:
(1) software method. like VFs for "Intel(R) Ethernet Controller XL710 Family
support".
(2) hardware method. through hardware internal buffer (as one Intel
internal hardware not yet to public, but very soon) or through VTD-3.0
IOMMU.

we have already had code verified using the two ways to track system memory
in fine-grained level.


> what has been pinned and then ideally put that memory off until the end.
> (Which is interesting because I don't think we currently have  a way
> to delay RAM pages till the end in qemu).

I think the problem here is that we mixed pinned pages with dirty pages.
yes, pinned pages for mdev devices are continuously likely to be dirty
until device stopped.
But for devices that are able to report dirty pages, dirtied pages
will be marked again if hardware writes them later.

So, is it good to introduce a capability to let vfio/qemu know how to
treat the dirty pages?
(1) for devices have no fine-grained dirty page tracking capability
  a. pinned pages are regarded as dirty pages. they are not cleared by
  dirty page query
  b. unpinned pages are regarded as dirty pages. they are cleared by
  dirty page query or UNMAP ioctl.
(2) for devices that have fine-grained dirty page tracking capability
   a. pinned/unpinned pages are not regarded as dirty pages
   b. only pages they reported are regarded as dirty pages and are to be
   cleared by dirty page query and UNMAP ioctl.
(3) for dirty pages marking APIs, like vfio_dma_rw()...
   pages marked by them are regared as dirty and are to be cleared by
   dirty page query and UNMAP ioctl

For (1), qemu VFIO only reports dirty page amount and would not transfer
those pages until last round.
for (2) and (3), qemu VFIO should report and transfer them in each
round.


> [I still worry whether migration will be usable with any
> significant amount of system ram that's pinned in this way; the
> downside will very easily get above the threshold that people like]
> 
yes. that's why we have to do multi-round dirty page query and
transfer and clear the dirty bitmaps in each round for devices that are
able to track in fine grain.
and that's why we have to report the amount of dirty pages before
stop-and-copy phase for mdev devices, so that people are able to know
the real downtime as much as possible.

Thanks
Yan


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-24  3:01                   ` Yan Zhao
@ 2020-03-24  9:45                     ` Kirti Wankhede
  2020-03-24 14:36                     ` Alex Williamson
  1 sibling, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-24  9:45 UTC (permalink / raw)
  To: Yan Zhao, Dr. David Alan Gilbert
  Cc: Zhengxiao.zx, Tian, Kevin, Liu, Yi L, cjia, kvm, eskultet, Yang,
	Ziye, cohuck, shuangtai.tst, qemu-devel, Wang,  Zhi A, mlevitsk,
	pasic, aik, Alex Williamson, eauger, felipe, jonathan.davies,
	Liu, Changpeng, Ken.Xue



On 3/24/2020 8:31 AM, Yan Zhao wrote:
> On Tue, Mar 24, 2020 at 02:51:14AM +0800, Dr. David Alan Gilbert wrote:
>> * Alex Williamson (alex.williamson@redhat.com) wrote:
>>> On Mon, 23 Mar 2020 23:24:37 +0530
>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>
>>>> On 3/21/2020 12:29 AM, Alex Williamson wrote:
>>>>> On Sat, 21 Mar 2020 00:12:04 +0530
>>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>>>    
>>>>>> On 3/20/2020 11:31 PM, Alex Williamson wrote:
>>>>>>> On Fri, 20 Mar 2020 23:19:14 +0530
>>>>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>>>>>       
>>>>>>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:
>>>>>>>>> On Fri, 20 Mar 2020 01:46:41 +0530
>>>>>>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>>>>>>>          
>>>>>>
>>>>>> <snip>
>>>>>>   
>>>>>>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
>>>>>>>>>> +				  size_t size, uint64_t pgsize,
>>>>>>>>>> +				  u64 __user *bitmap)
>>>>>>>>>> +{
>>>>>>>>>> +	struct vfio_dma *dma;
>>>>>>>>>> +	unsigned long pgshift = __ffs(pgsize);
>>>>>>>>>> +	unsigned int npages, bitmap_size;
>>>>>>>>>> +
>>>>>>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
>>>>>>>>>> +
>>>>>>>>>> +	if (!dma)
>>>>>>>>>> +		return -EINVAL;
>>>>>>>>>> +
>>>>>>>>>> +	if (dma->iova != iova || dma->size != size)
>>>>>>>>>> +		return -EINVAL;
>>>>>>>>>> +
>>>>>>>>>> +	npages = dma->size >> pgshift;
>>>>>>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
>>>>>>>>>> +
>>>>>>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
>>>>>>>>>> +	if (dma->iommu_mapped)
>>>>>>>>>> +		bitmap_set(dma->bitmap, 0, npages);
>>>>>>>>>> +
>>>>>>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
>>>>>>>>>> +		return -EFAULT;
>>>>>>>>>
>>>>>>>>> We still need to reset the bitmap here, clearing and re-adding the
>>>>>>>>> pages that are still pinned.
>>>>>>>>>
>>>>>>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
>>>>>>>>>          
>>>>>>>>
>>>>>>>> I thought you agreed on my reply to it
>>>>>>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
>>>>>>>>      
>>>>>>>>     > Why re-populate when there will be no change since
>>>>>>>>     > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
>>>>>>>>     > pin request while vfio_iova_dirty_bitmap() is still working, it will
>>>>>>>>     > wait till iommu->lock is released. Bitmap will be populated when page is
>>>>>>>>     > pinned.
>>>>>>>
>>>>>>> As coded, dirty bits are only ever set in the bitmap, never cleared.
>>>>>>> If a page is unpinned between iterations of the user recording the
>>>>>>> dirty bitmap, it should be marked dirty in the iteration immediately
>>>>>>> after the unpinning and not marked dirty in the following iteration.
>>>>>>> That doesn't happen here.  We're reporting cumulative dirty pages since
>>>>>>> logging was enabled, we need to be reporting dirty pages since the user
>>>>>>> last retrieved the dirty bitmap.  The bitmap should be cleared and
>>>>>>> currently pinned pages re-added after copying to the user.  Thanks,
>>>>>>>       
>>>>>>
>>>>>> Does that mean, we have to track every iteration? do we really need that
>>>>>> tracking?
>>>>>>
>>>>>> Generally the flow is:
>>>>>> - vendor driver pin x pages
>>>>>> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
>>>>>> tracking, then user asks dirty bitmap, x pages reported dirty by
>>>>>> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
>>>>>> - In pre-copy phase, vendor driver pins y more pages, now bitmap
>>>>>> consists of x+y bits set
>>>>>> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
>>>>>> updated, so again bitmap consists of x+y bits set.
>>>>>> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
>>>>>> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
>>>>>> pages should not get dirty by guest driver or the physical device.
>>>>>> Hence, x+y dirty pages would be reported.
>>>>>>
>>>>>> I don't think we need to track every iteration of bitmap reporting.
>>>>>
>>>>> Yes, once a bitmap is read, it's reset.  In your example, after
>>>>> unpinning z pages the user should still see a bitmap with x+y pages,
>>>>> but once they've read that bitmap, the next bitmap should be x+y-z.
>>>>> Userspace can make decisions about when to switch from pre-copy to
>>>>> stop-and-copy based on convergence, ie. the slope of the line recording
>>>>> dirty pages per iteration.  The implementation here never allows an
>>>>> inflection point, dirty pages reported through vfio would always either
>>>>> be flat or climbing.  There might also be a case that an iommu backed
>>>>> device could start pinning pages during the course of a migration, how
>>>>> would the bitmap ever revert from fully populated to only tracking the
>>>>> pinned pages?  Thanks,
>>>>>    
>>>>
>>>> At KVM forum we discussed this - if guest driver pins say 1024 pages
>>>> before migration starts, during pre-copy phase device can dirty 0 pages
>>>> in best case and 1024 pages in worst case. In that case, user will
>>>> transfer content of 1024 pages during pre-copy phase and in
>>>> stop-and-copy phase also, that will be pages will be copied twice. So we
>>>> decided to only get dirty pages bitmap at stop-and-copy phase. If user
>>>> is going to get dirty pages in stop-and-copy phase only, then that will
>>>> be single iteration.
>>>> There aren't any devices yet that can track sys memory dirty pages. So
>>>> we can go ahead with this patch and support for dirty pages tracking
>>>> during pre-copy phase can be added later when there will be consumers of
>>>> that functionality.
>>>
>>> So if I understand this right, you're expecting the dirty bitmap to
>>> accumulate dirty bits, in perpetuity, so that the user can only
>>> retrieve them once at the end of migration?  But if that's the case,
>>> the user could simply choose to not retrieve the bitmap until the end
>>> of migration, the result would be the same.  What we have here is that
>>> dirty bits are never cleared, regardless of whether the user has seen
>>> them, which is wrong.  Sorry, we had a lot of discussions at KVM forum,
>>> I don't recall this specific one 5 months later and maybe we weren't
>>> considering all aspects.  I see the behavior we have here as incorrect,
>>> but it also seems relatively trivial to make correct.  I hope the QEMU
>>> code isn't making us go through all this trouble to report a dirty
>>> bitmap that gets thrown away because it expects the final one to be
>>> cumulative since the beginning of dirty logging.  Thanks,
>>
>> I remember the discussion that we couldn't track the system memory
>> dirtying with current hardware; so the question then is just to track

> hi Dave
> there are already devices that are able to track the system memory,
> through two ways:
> (1) software method. like VFs for "Intel(R) Ethernet Controller XL710 Family
> support".
> (2) hardware method. through hardware internal buffer (as one Intel
> internal hardware not yet to public, but very soon) or through VTD-3.0
> IOMMU.
> 
> we have already had code verified using the two ways to track system memory
> in fine-grained level.
> 
> 
>> what has been pinned and then ideally put that memory off until the end.
>> (Which is interesting because I don't think we currently have  a way
>> to delay RAM pages till the end in qemu).
> 
> I think the problem here is that we mixed pinned pages with dirty pages.
> yes, pinned pages for mdev devices are continuously likely to be dirty
> until device stopped.
> But for devices that are able to report dirty pages, dirtied pages
> will be marked again if hardware writes them later.
> 
> So, is it good to introduce a capability to let vfio/qemu know how to
> treat the dirty pages?
> (1) for devices have no fine-grained dirty page tracking capability
>    a. pinned pages are regarded as dirty pages. they are not cleared by
>    dirty page query
>    b. unpinned pages are regarded as dirty pages. they are cleared by
>    dirty page query or UNMAP ioctl.
> (2) for devices that have fine-grained dirty page tracking capability
>     a. pinned/unpinned pages are not regarded as dirty pages
>     b. only pages they reported are regarded as dirty pages and are to be
>     cleared by dirty page query and UNMAP ioctl.
> (3) for dirty pages marking APIs, like vfio_dma_rw()...
>     pages marked by them are regared as dirty and are to be cleared by
>     dirty page query and UNMAP ioctl
> 
> For (1), qemu VFIO only reports dirty page amount and would not transfer
> those pages until last round.

(1) and (3) can be implemented now. I don't think QEMU have support to 
delay certain marked pages dirty as of now. If QEMU queries dirty pages 
bitmap in pre-copy phase, all pinned pages reported as dirty will be 
transferred in pre-copy and again in stop-and-copy phase.

> for (2) and (3), qemu VFIO should report and transfer them in each
> round.
>

(2) can be added later

Thanks,
Kirti

> 
>> [I still worry whether migration will be usable with any
>> significant amount of system ram that's pinned in this way; the
>> downside will very easily get above the threshold that people like]
>>
> yes. that's why we have to do multi-round dirty page query and
> transfer and clear the dirty bitmaps in each round for devices that are
> able to track in fine grain.
> and that's why we have to report the amount of dirty pages before
> stop-and-copy phase for mdev devices, so that people are able to know
> the real downtime as much as possible.
> 
> Thanks
> Yan
> 


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-24  3:01                   ` Yan Zhao
  2020-03-24  9:45                     ` Kirti Wankhede
@ 2020-03-24 14:36                     ` Alex Williamson
  2020-03-24 20:23                       ` Dr. David Alan Gilbert
  1 sibling, 1 reply; 29+ messages in thread
From: Alex Williamson @ 2020-03-24 14:36 UTC (permalink / raw)
  To: Yan Zhao
  Cc: Zhengxiao.zx, Tian, Kevin, Liu, Yi L, cjia, kvm, eskultet, Yang,
	Ziye, qemu-devel, cohuck, shuangtai.tst, Dr. David Alan Gilbert,
	Wang, Zhi A, mlevitsk, pasic, aik, Kirti Wankhede, eauger,
	felipe, jonathan.davies, Liu,  Changpeng, Ken.Xue

On Mon, 23 Mar 2020 23:01:18 -0400
Yan Zhao <yan.y.zhao@intel.com> wrote:

> On Tue, Mar 24, 2020 at 02:51:14AM +0800, Dr. David Alan Gilbert wrote:
> > * Alex Williamson (alex.williamson@redhat.com) wrote:  
> > > On Mon, 23 Mar 2020 23:24:37 +0530
> > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > >   
> > > > On 3/21/2020 12:29 AM, Alex Williamson wrote:  
> > > > > On Sat, 21 Mar 2020 00:12:04 +0530
> > > > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > >     
> > > > >> On 3/20/2020 11:31 PM, Alex Williamson wrote:    
> > > > >>> On Fri, 20 Mar 2020 23:19:14 +0530
> > > > >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > >>>        
> > > > >>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:    
> > > > >>>>> On Fri, 20 Mar 2020 01:46:41 +0530
> > > > >>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > >>>>>           
> > > > >>
> > > > >> <snip>
> > > > >>    
> > > > >>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> > > > >>>>>> +				  size_t size, uint64_t pgsize,
> > > > >>>>>> +				  u64 __user *bitmap)
> > > > >>>>>> +{
> > > > >>>>>> +	struct vfio_dma *dma;
> > > > >>>>>> +	unsigned long pgshift = __ffs(pgsize);
> > > > >>>>>> +	unsigned int npages, bitmap_size;
> > > > >>>>>> +
> > > > >>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
> > > > >>>>>> +
> > > > >>>>>> +	if (!dma)
> > > > >>>>>> +		return -EINVAL;
> > > > >>>>>> +
> > > > >>>>>> +	if (dma->iova != iova || dma->size != size)
> > > > >>>>>> +		return -EINVAL;
> > > > >>>>>> +
> > > > >>>>>> +	npages = dma->size >> pgshift;
> > > > >>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> > > > >>>>>> +
> > > > >>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
> > > > >>>>>> +	if (dma->iommu_mapped)
> > > > >>>>>> +		bitmap_set(dma->bitmap, 0, npages);
> > > > >>>>>> +
> > > > >>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> > > > >>>>>> +		return -EFAULT;    
> > > > >>>>>
> > > > >>>>> We still need to reset the bitmap here, clearing and re-adding the
> > > > >>>>> pages that are still pinned.
> > > > >>>>>
> > > > >>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> > > > >>>>>           
> > > > >>>>
> > > > >>>> I thought you agreed on my reply to it
> > > > >>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> > > > >>>>       
> > > > >>>>    > Why re-populate when there will be no change since
> > > > >>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
> > > > >>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it will
> > > > >>>>    > wait till iommu->lock is released. Bitmap will be populated when page is
> > > > >>>>    > pinned.    
> > > > >>>
> > > > >>> As coded, dirty bits are only ever set in the bitmap, never cleared.
> > > > >>> If a page is unpinned between iterations of the user recording the
> > > > >>> dirty bitmap, it should be marked dirty in the iteration immediately
> > > > >>> after the unpinning and not marked dirty in the following iteration.
> > > > >>> That doesn't happen here.  We're reporting cumulative dirty pages since
> > > > >>> logging was enabled, we need to be reporting dirty pages since the user
> > > > >>> last retrieved the dirty bitmap.  The bitmap should be cleared and
> > > > >>> currently pinned pages re-added after copying to the user.  Thanks,
> > > > >>>        
> > > > >>
> > > > >> Does that mean, we have to track every iteration? do we really need that
> > > > >> tracking?
> > > > >>
> > > > >> Generally the flow is:
> > > > >> - vendor driver pin x pages
> > > > >> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
> > > > >> tracking, then user asks dirty bitmap, x pages reported dirty by
> > > > >> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> > > > >> - In pre-copy phase, vendor driver pins y more pages, now bitmap
> > > > >> consists of x+y bits set
> > > > >> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
> > > > >> updated, so again bitmap consists of x+y bits set.
> > > > >> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
> > > > >> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
> > > > >> pages should not get dirty by guest driver or the physical device.
> > > > >> Hence, x+y dirty pages would be reported.
> > > > >>
> > > > >> I don't think we need to track every iteration of bitmap reporting.    
> > > > > 
> > > > > Yes, once a bitmap is read, it's reset.  In your example, after
> > > > > unpinning z pages the user should still see a bitmap with x+y pages,
> > > > > but once they've read that bitmap, the next bitmap should be x+y-z.
> > > > > Userspace can make decisions about when to switch from pre-copy to
> > > > > stop-and-copy based on convergence, ie. the slope of the line recording
> > > > > dirty pages per iteration.  The implementation here never allows an
> > > > > inflection point, dirty pages reported through vfio would always either
> > > > > be flat or climbing.  There might also be a case that an iommu backed
> > > > > device could start pinning pages during the course of a migration, how
> > > > > would the bitmap ever revert from fully populated to only tracking the
> > > > > pinned pages?  Thanks,
> > > > >     
> > > > 
> > > > At KVM forum we discussed this - if guest driver pins say 1024 pages 
> > > > before migration starts, during pre-copy phase device can dirty 0 pages 
> > > > in best case and 1024 pages in worst case. In that case, user will 
> > > > transfer content of 1024 pages during pre-copy phase and in 
> > > > stop-and-copy phase also, that will be pages will be copied twice. So we 
> > > > decided to only get dirty pages bitmap at stop-and-copy phase. If user 
> > > > is going to get dirty pages in stop-and-copy phase only, then that will 
> > > > be single iteration.
> > > > There aren't any devices yet that can track sys memory dirty pages. So 
> > > > we can go ahead with this patch and support for dirty pages tracking 
> > > > during pre-copy phase can be added later when there will be consumers of 
> > > > that functionality.  
> > > 
> > > So if I understand this right, you're expecting the dirty bitmap to
> > > accumulate dirty bits, in perpetuity, so that the user can only
> > > retrieve them once at the end of migration?  But if that's the case,
> > > the user could simply choose to not retrieve the bitmap until the end
> > > of migration, the result would be the same.  What we have here is that
> > > dirty bits are never cleared, regardless of whether the user has seen
> > > them, which is wrong.  Sorry, we had a lot of discussions at KVM forum,
> > > I don't recall this specific one 5 months later and maybe we weren't
> > > considering all aspects.  I see the behavior we have here as incorrect,
> > > but it also seems relatively trivial to make correct.  I hope the QEMU
> > > code isn't making us go through all this trouble to report a dirty
> > > bitmap that gets thrown away because it expects the final one to be
> > > cumulative since the beginning of dirty logging.  Thanks,  
> > 
> > I remember the discussion that we couldn't track the system memory
> > dirtying with current hardware; so the question then is just to track  
> hi Dave
> there are already devices that are able to track the system memory,
> through two ways:
> (1) software method. like VFs for "Intel(R) Ethernet Controller XL710 Family
> support".
> (2) hardware method. through hardware internal buffer (as one Intel
> internal hardware not yet to public, but very soon) or through VTD-3.0
> IOMMU.
> 
> we have already had code verified using the two ways to track system memory
> in fine-grained level.
> 
> 
> > what has been pinned and then ideally put that memory off until the end.
> > (Which is interesting because I don't think we currently have  a way
> > to delay RAM pages till the end in qemu).  
> 
> I think the problem here is that we mixed pinned pages with dirty pages.

We are reporting dirty pages, pinned pages are just assumed to be dirty.

> yes, pinned pages for mdev devices are continuously likely to be dirty
> until device stopped.
> But for devices that are able to report dirty pages, dirtied pages
> will be marked again if hardware writes them later.
> 
> So, is it good to introduce a capability to let vfio/qemu know how to
> treat the dirty pages?

Dirty pages are dirty, QEMU doesn't need any special flag, instead we
need to evolve different mechanisms for the vendor driver so that we
can differentiate pages pinned for read vs pages pinned for write.
Perhaps interfaces to pin pages without dirtying them, and a separate
mechanism to dirty a previously pinned-page, ie. promote it permanently
or transiently to a writable page.

> (1) for devices have no fine-grained dirty page tracking capability
>   a. pinned pages are regarded as dirty pages. they are not cleared by
>   dirty page query
>   b. unpinned pages are regarded as dirty pages. they are cleared by
>   dirty page query or UNMAP ioctl.
> (2) for devices that have fine-grained dirty page tracking capability
>    a. pinned/unpinned pages are not regarded as dirty pages

We need a pin-read-only interface for this.

>    b. only pages they reported are regarded as dirty pages and are to be
>    cleared by dirty page query and UNMAP ioctl.

We need a set-dirty or promote-writable interface for this.

> (3) for dirty pages marking APIs, like vfio_dma_rw()...
>    pages marked by them are regared as dirty and are to be cleared by
>    dirty page query and UNMAP ioctl
> 
> For (1), qemu VFIO only reports dirty page amount and would not transfer
> those pages until last round.
> for (2) and (3), qemu VFIO should report and transfer them in each
> round.

IMO, QEMU should not be aware of any of this.  Userspace has an
interface to retrieve dirtied pages (period).  We should adjust the
pages that we report as dirtied to be accurate based on the
capabilities of the vendor driver.  We can evolve those internal APIs
between the vendor driver and vfio iommu over time without modifying
this user interface.

> > [I still worry whether migration will be usable with any
> > significant amount of system ram that's pinned in this way; the
> > downside will very easily get above the threshold that people like]
> >   
> yes. that's why we have to do multi-round dirty page query and
> transfer and clear the dirty bitmaps in each round for devices that are
> able to track in fine grain.
> and that's why we have to report the amount of dirty pages before
> stop-and-copy phase for mdev devices, so that people are able to know
> the real downtime as much as possible.

Yes, the dirty bitmap should be accurate to report the pages dirtied
since it was last retrieved and over time we can add internal
interfaces to give vendor drivers more granularity in marking pinned
pages dirty and perhaps even exposing the bitmap to the vendor drivers
to set pages themselves.  I don't necessarily think it's worthwhile to
create a new class of dirtied pages to transfer at the end, we're
fighting a losing battle at that point.  We should be focusing on
improving the granularity of page dirtying in order to reduce the pages
transferred at the end of migration.  Thanks,

Alex



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state
  2020-03-23 20:30   ` Auger Eric
@ 2020-03-24 19:31     ` Kirti Wankhede
  0 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-24 19:31 UTC (permalink / raw)
  To: Auger Eric, alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue



On 3/24/2020 2:00 AM, Auger Eric wrote:
> Hi Kirti,
> 
> On 3/19/20 9:16 PM, Kirti Wankhede wrote:
>> - Defined MIGRATION region type and sub-type.
>>
>> - Defined vfio_device_migration_info structure which will be placed at the
>>    0th offset of migration region to get/set VFIO device related
>>    information. Defined members of structure and usage on read/write access.
>>
>> - Defined device states and state transition details.
>>
>> - Defined sequence to be followed while saving and resuming VFIO device.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> Reviewed-by: Neo Jia <cjia@nvidia.com>
> 
> Please forgive me, I have just discovered v15 was available.
> 
> hereafter, you will find the 2 main points I feel difficult to
> understand when reading the documentation.
> 
>> ---
>>   include/uapi/linux/vfio.h | 227 ++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 227 insertions(+)
>>
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index 9e843a147ead..d0021467af53 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -305,6 +305,7 @@ struct vfio_region_info_cap_type {
>>   #define VFIO_REGION_TYPE_PCI_VENDOR_MASK	(0xffff)
>>   #define VFIO_REGION_TYPE_GFX                    (1)
>>   #define VFIO_REGION_TYPE_CCW			(2)
>> +#define VFIO_REGION_TYPE_MIGRATION              (3)
>>   
>>   /* sub-types for VFIO_REGION_TYPE_PCI_* */
>>   
>> @@ -379,6 +380,232 @@ struct vfio_region_gfx_edid {
>>   /* sub-types for VFIO_REGION_TYPE_CCW */
>>   #define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD	(1)
>>   
>> +/* sub-types for VFIO_REGION_TYPE_MIGRATION */
>> +#define VFIO_REGION_SUBTYPE_MIGRATION           (1)
>> +
>> +/*
>> + * The structure vfio_device_migration_info is placed at the 0th offset of
>> + * the VFIO_REGION_SUBTYPE_MIGRATION region to get and set VFIO device related
>> + * migration information. Field accesses from this structure are only supported
>> + * at their native width and alignment. Otherwise, the result is undefined and
>> + * vendor drivers should return an error.
>> + *
>> + * device_state: (read/write)
>> + *      - The user application writes to this field to inform the vendor driver
>> + *        about the device state to be transitioned to.
>> + *      - The vendor driver should take the necessary actions to change the
>> + *        device state. After successful transition to a given state, the
>> + *        vendor driver should return success on write(device_state, state)
>> + *        system call. If the device state transition fails, the vendor driver
>> + *        should return an appropriate -errno for the fault condition.
>> + *      - On the user application side, if the device state transition fails,
>> + *	  that is, if write(device_state, state) returns an error, read
>> + *	  device_state again to determine the current state of the device from
>> + *	  the vendor driver.
>> + *      - The vendor driver should return previous state of the device unless
>> + *        the vendor driver has encountered an internal error, in which case
>> + *        the vendor driver may report the device_state VFIO_DEVICE_STATE_ERROR.
>> + *      - The user application must use the device reset ioctl to recover the
>> + *        device from VFIO_DEVICE_STATE_ERROR state. If the device is
>> + *        indicated to be in a valid device state by reading device_state, the
>> + *        user application may attempt to transition the device to any valid
>> + *        state reachable from the current state or terminate itself.
>> + *
>> + *      device_state consists of 3 bits:
>> + *      - If bit 0 is set, it indicates the _RUNNING state. If bit 0 is clear,
>> + *        it indicates the _STOP state. When the device state is changed to
>> + *        _STOP, driver should stop the device before write() returns.
>> + *      - If bit 1 is set, it indicates the _SAVING state, which means that the
>> + *        driver should start gathering device state information that will be
>> + *        provided to the VFIO user application to save the device's state.
>> + *      - If bit 2 is set, it indicates the _RESUMING state, which means that
>> + *        the driver should prepare to resume the device. Data provided through
>> + *        the migration region should be used to resume the device.
>> + *      Bits 3 - 31 are reserved for future use. To preserve them, the user
>> + *      application should perform a read-modify-write operation on this
>> + *      field when modifying the specified bits.
>> + *
>> + *  +------- _RESUMING
>> + *  |+------ _SAVING
>> + *  ||+----- _RUNNING
>> + *  |||
>> + *  000b => Device Stopped, not saving or resuming
>> + *  001b => Device running, which is the default state
>> + *  010b => Stop the device & save the device state, stop-and-copy state
>> + *  011b => Device running and save the device state, pre-copy state
>> + *  100b => Device stopped and the device state is resuming
>> + *  101b => Invalid state
>> + *  110b => Error state
>> + *  111b => Invalid state
>> + *
>> + * State transitions:
>> + *
>> + *              _RESUMING  _RUNNING    Pre-copy    Stop-and-copy   _STOP
>> + *                (100b)     (001b)     (011b)        (010b)       (000b)
>> + * 0. Running or default state
>> + *                             |
>> + *
>> + * 1. Normal Shutdown (optional)
>> + *                             |------------------------------------->|
>> + *
>> + * 2. Save the state or suspend
>> + *                             |------------------------->|---------->|
>> + *
>> + * 3. Save the state during live migration
>> + *                             |----------->|------------>|---------->|
>> + *
>> + * 4. Resuming
>> + *                  |<---------|
>> + *
>> + * 5. Resumed
>> + *                  |--------->|
>> + *
>> + * 0. Default state of VFIO device is _RUNNNG when the user application starts.
>> + * 1. During normal shutdown of the user application, the user application may
>> + *    optionally change the VFIO device state from _RUNNING to _STOP. This
>> + *    transition is optional. The vendor driver must support this transition but
>> + *    must not require it.
>> + * 2. When the user application saves state or suspends the application, the
>> + *    device state transitions from _RUNNING to stop-and-copy and then to _STOP.
>> + *    On state transition from _RUNNING to stop-and-copy, driver must stop the
>> + *    device, save the device state and send it to the application through the
>> + *    migration region. The sequence to be followed for such transition is given
>> + *    below.
>> + * 3. In live migration of user application, the state transitions from _RUNNING
>> + *    to pre-copy, to stop-and-copy, and to _STOP.
>> + *    On state transition from _RUNNING to pre-copy, the driver should start
>> + *    gathering the device state while the application is still running and send
>> + *    the device state data to application through the migration region.
>> + *    On state transition from pre-copy to stop-and-copy, the driver must stop
>> + *    the device, save the device state and send it to the user application
>> + *    through the migration region.
>> + *    Vendor drivers must support the pre-copy state even for implementations
>> + *    where no data is provided to the user before the stop-and-copy state. The
>> + *    user must not be required to consume all migration data before the device
>> + *    transitions to a new state, including the stop-and-copy state.
>> + *    The sequence to be followed for above two transitions is given below.
>> + * 4. To start the resuming phase, the device state should be transitioned from
>> + *    the _RUNNING to the _RESUMING state.
>> + *    In the _RESUMING state, the driver should use the device state data
>> + *    received through the migration region to resume the device.
>> + * 5. After providing saved device data to the driver, the application should
>> + *    change the state from _RESUMING to _RUNNING.
>> + *
>> + * reserved:
>> + *      Reads on this field return zero and writes are ignored.
>> + *
>> + * pending_bytes: (read only)
>> + *      The number of pending bytes still to be migrated from the vendor driver.
>> + *
>> + * data_offset: (read only)
>> + *      The user application should read data_offset in the migration region
>> + *      from where the user application should read the device data during the
>> + *      _SAVING state or write the device data during the _RESUMING state. See
>> + *      below for details of sequence to be followed.
>> + *
>> + * data_size: (read/write)
>> + *      The user application should read data_size to get the size in bytes of
>> + *      the data copied in the migration region during the _SAVING state and
>> + *      write the size in bytes of the data copied in the migration region
>> + *      during the _RESUMING state.
>> + *
>> + * The format of the migration region is as follows:
>> + *  ------------------------------------------------------------------
>> + * |vfio_device_migration_info|    data section                      |
>> + * |                          |     ///////////////////////////////  |
>> + * ------------------------------------------------------------------
>> + *   ^                              ^
>> + *  offset 0-trapped part        data_offset
>> + *
>> + * The structure vfio_device_migration_info is always followed by the data
>> + * section in the region, so data_offset will always be nonzero. The offset
>> + * from where the data is copied is decided by the kernel driver. The data
>> + * section can be trapped, mapped, or partitioned, depending on how the kernel
>> + * driver defines the data section. The data section partition can be defined
>> + * as mapped by the sparse mmap capability. If mmapped, data_offset should be
>> + * page aligned, whereas initial section which contains the
>> + * vfio_device_migration_info structure, might not end at the offset, which is
>> + * page aligned. The user is not required to access through mmap regardless
>> + * of the capabilities of the region mmap.
>> + * The vendor driver should determine whether and how to partition the data
>> + * section. The vendor driver should return data_offset accordingly.
>> + *
>> + * The sequence to be followed for the _SAVING|_RUNNING device state or
>> + * pre-copy phase and for the _SAVING device state or stop-and-copy phase is as
>> + * follows:
>> + * a. Read pending_bytes, indicating the start of a new iteration to get device
>> + *    data. Repeated read on pending_bytes at this stage should have no side
>> + *    effects.
>> + *    If pending_bytes == 0, the user application should not iterate to get data
>> + *    for that device.
> I do not feel comfortable with the above sentence. In pre-save state,
> the device is running and I understand nothing prevents from getting new
> state data even after the pending_bytes reached 0.

If pending_bytes == 0 that means that vendor driver don't have device 
data anymore. This sequence is for both, pre-copy and stop-and-copy state.
During pre-copy state, there might be 2 cases:
pending_bytes !=0 => vendor driver still has data, but user application 
decides to transition to next state, stop-and-copy state.
pending_bytes == 0 => vendor driver has collected data till some check 
point and given to user application, so vendor driver doesn't have any 
more data to transfer. Vendor driver can track data after that check 
point for stop-and-copy state. Or vendor driver doesn't support pre-copy 
state or doesn't want to send any data in pre-copy state.

>> + *    If pending_bytes > 0, perform the following steps.
>> + * b. Read data_offset, indicating that the vendor driver should make data
>> + *    available through the data section. The vendor driver should return this
>> + *    read operation only after data is available from (region + data_offset)
>> + *    to (region + data_offset + data_size).
>> + * c. Read data_size, which is the amount of data in bytes available through
>> + *    the migration region.
>> + *    Read on data_offset and data_size should return the offset and size of
>> + *    the current buffer if the user application reads data_offset and
>> + *    data_size more than once here.
>> + * d. Read data_size bytes of data from (region + data_offset) from the
>> + *    migration region.
>> + * e. Process the data.
>> + * f. Read pending_bytes, which indicates that the data from the previous
>> + *    iteration has been read. If pending_bytes > 0, go to step b.
>> + *
>> + * If an error occurs during the above sequence, the vendor driver can return
>> + * an error code for next read() or write() operation, which will terminate the
>> + * loop. The user application should then take the next necessary action, for
>> + * example, failing migration or terminating the user application.> + *
>> + * The user application can transition from the _SAVING|_RUNNING
>> + * (pre-copy state) to the _SAVING (stop-and-copy) state regardless of the
>> + * number of pending bytes. The user application should iterate in _SAVING
>> + * (stop-and-copy) until pending_bytes is 0.
>> + *
>> + * The sequence to be followed while _RESUMING device state is as follows:
>> + * While data for this device is available, repeat the following steps:
>> + * a. Read data_offset from where the user application should write data.
>> + * b. Write migration data starting at the migration region + data_offset for
>> + *    the length determined by data_size from the migration source.
>> + * c. Write data_size, which indicates to the vendor driver that data is
>> + *    written in the migration region. Vendor driver should apply the
>> + *    user-provided migration region data to the device resume state.
> This is not clear to me when the data gets consumed by the device. Is
> the write data_size blocking?

Yes.
As mentioned in my reply to v14 patch, on write(data_size), vendor 
driver should return only after consuming data, Updating it as below:

  * c. Write data_size, which indicates to the vendor driver that data is
  *    written in the migration region. Vendor driver must return this write
  *    operations on consuming data. Vendor driver should apply the
  *    user-provided migration region data to the device resume state.

Thanks,
Kirti

> Is the data offset moving to make sure the
> user data will not be overriden? Can the the userapp refill immediately?
> At least some hints about possible implementation would ease the
> understanding.
> 
> Thanks
> 
> Eric
>> + *
>> + * For the user application, data is opaque. The user application should write
>> + * data in the same order as the data is received and the data should be of
>> + * same transaction size at the source.
>> + */
>> +
>> +struct vfio_device_migration_info {
>> +	__u32 device_state;         /* VFIO device state */
>> +#define VFIO_DEVICE_STATE_STOP      (0)
>> +#define VFIO_DEVICE_STATE_RUNNING   (1 << 0)
>> +#define VFIO_DEVICE_STATE_SAVING    (1 << 1)
>> +#define VFIO_DEVICE_STATE_RESUMING  (1 << 2)
>> +#define VFIO_DEVICE_STATE_MASK      (VFIO_DEVICE_STATE_RUNNING | \
>> +				     VFIO_DEVICE_STATE_SAVING |  \
>> +				     VFIO_DEVICE_STATE_RESUMING)
>> +
>> +#define VFIO_DEVICE_STATE_VALID(state) \
>> +	(state & VFIO_DEVICE_STATE_RESUMING ? \
>> +	(state & VFIO_DEVICE_STATE_MASK) == VFIO_DEVICE_STATE_RESUMING : 1)
>> +
>> +#define VFIO_DEVICE_STATE_IS_ERROR(state) \
>> +	((state & VFIO_DEVICE_STATE_MASK) == (VFIO_DEVICE_STATE_SAVING | \
>> +					      VFIO_DEVICE_STATE_RESUMING))
>> +
>> +#define VFIO_DEVICE_STATE_SET_ERROR(state) \
>> +	((state & ~VFIO_DEVICE_STATE_MASK) | VFIO_DEVICE_SATE_SAVING | \
>> +					     VFIO_DEVICE_STATE_RESUMING)
>> +
>> +	__u32 reserved;
>> +	__u64 pending_bytes;
>> +	__u64 data_offset;
>> +	__u64 data_size;
>> +} __attribute__((packed));
>> +
>>   /*
>>    * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
>>    * which allows direct access to non-MSIX registers which happened to be within
>>
> 


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages
  2020-03-23 20:30   ` Auger Eric
@ 2020-03-24 19:34     ` Kirti Wankhede
  0 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-24 19:34 UTC (permalink / raw)
  To: Auger Eric, alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue



On 3/24/2020 2:00 AM, Auger Eric wrote:
> Hi Kirti,
> 
> On 3/19/20 9:16 PM, Kirti Wankhede wrote:
>> vfio_pfn.ref_count is always updated by holding iommu->lock, using atomic
>> variable is overkill.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> Reviewed-by: Neo Jia <cjia@nvidia.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> 

Thanks.

Kirti.

> Thanks
> 
> Eric
>> ---
>>   drivers/vfio/vfio_iommu_type1.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 9fdfae1cb17a..70aeab921d0f 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -112,7 +112,7 @@ struct vfio_pfn {
>>   	struct rb_node		node;
>>   	dma_addr_t		iova;		/* Device address */
>>   	unsigned long		pfn;		/* Host pfn */
>> -	atomic_t		ref_count;
>> +	unsigned int		ref_count;
>>   };
>>   
>>   struct vfio_regions {
>> @@ -233,7 +233,7 @@ static int vfio_add_to_pfn_list(struct vfio_dma *dma, dma_addr_t iova,
>>   
>>   	vpfn->iova = iova;
>>   	vpfn->pfn = pfn;
>> -	atomic_set(&vpfn->ref_count, 1);
>> +	vpfn->ref_count = 1;
>>   	vfio_link_pfn(dma, vpfn);
>>   	return 0;
>>   }
>> @@ -251,7 +251,7 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
>>   	struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
>>   
>>   	if (vpfn)
>> -		atomic_inc(&vpfn->ref_count);
>> +		vpfn->ref_count++;
>>   	return vpfn;
>>   }
>>   
>> @@ -259,7 +259,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
>>   {
>>   	int ret = 0;
>>   
>> -	if (atomic_dec_and_test(&vpfn->ref_count)) {
>> +	vpfn->ref_count--;
>> +	if (!vpfn->ref_count) {
>>   		ret = put_pfn(vpfn->pfn, dma->prot);
>>   		vfio_remove_from_pfn_list(dma, vpfn);
>>   	}
>>
> 


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking.
  2020-03-23 21:11   ` Auger Eric
@ 2020-03-24 19:49     ` Kirti Wankhede
  0 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-24 19:49 UTC (permalink / raw)
  To: Auger Eric, alex.williamson, cjia
  Cc: Zhengxiao.zx, kevin.tian, yi.l.liu, yan.y.zhao, kvm, eskultet,
	ziye.yang, qemu-devel, cohuck, shuangtai.tst, dgilbert,
	zhi.a.wang, mlevitsk, pasic, aik, eauger, felipe,
	jonathan.davies, changpeng.liu, Ken.Xue



On 3/24/2020 2:41 AM, Auger Eric wrote:
> Hi Kirti,
> 
> On 3/19/20 9:16 PM, Kirti Wankhede wrote:
>> IOMMU container maintains a list of all pages pinned by vfio_pin_pages API.
>> All pages pinned by vendor driver through this API should be considered as
>> dirty during migration. When container consists of IOMMU capable device and
>> all pages are pinned and mapped, then all pages are marked dirty.
>> Added support to start/stop dirtied pages tracking and to get bitmap of all
>> dirtied pages for requested IO virtual address range.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>> ---
>>   include/uapi/linux/vfio.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 55 insertions(+)
>>
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index d0021467af53..8138f94cac15 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -995,6 +995,12 @@ struct vfio_iommu_type1_dma_map {
>>   
>>   #define VFIO_IOMMU_MAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 13)
>>   
>> +struct vfio_bitmap {
>> +	__u64        pgsize;	/* page size for bitmap */
> in bytes as well

Added.

>> +	__u64        size;	/* in bytes */
>> +	__u64 __user *data;	/* one bit per page */
>> +};
>> +
>>   /**
>>    * VFIO_IOMMU_UNMAP_DMA - _IOWR(VFIO_TYPE, VFIO_BASE + 14,
>>    *							struct vfio_dma_unmap)
>> @@ -1021,6 +1027,55 @@ struct vfio_iommu_type1_dma_unmap {
>>   #define VFIO_IOMMU_ENABLE	_IO(VFIO_TYPE, VFIO_BASE + 15)
>>   #define VFIO_IOMMU_DISABLE	_IO(VFIO_TYPE, VFIO_BASE + 16)
>>   
>> +/**
>> + * VFIO_IOMMU_DIRTY_PAGES - _IOWR(VFIO_TYPE, VFIO_BASE + 17,
>> + *                                     struct vfio_iommu_type1_dirty_bitmap)
>> + * IOCTL is used for dirty pages tracking. Caller sets argsz, which is size of> + * struct vfio_iommu_type1_dirty_bitmap.
> nit: This may become outdated when adding new fields. argz use mode is
> documented at the beginning of the file.
>

Ok.

>   Caller set flag depend on which
>> + * operation to perform, details as below:
>> + *
>> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_START set, indicates
>> + * migration is active and IOMMU module should track pages which are dirtied or
>> + * potentially dirtied by device.
>> + * Dirty pages are tracked until tracking is stopped by user application by
>> + * setting VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP flag.
>> + *
>> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP set, indicates
>> + * IOMMU should stop tracking dirtied pages.
>> + *
>> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP flag set,
>> + * IOCTL returns dirty pages bitmap for IOMMU container during migration for
>> + * given IOVA range. User must provide data[] as the structure
>> + * vfio_iommu_type1_dirty_bitmap_get through which user provides IOVA range
> I think the fact the IOVA range must match the vfio dma_size must be
> documented.

Added.

>   and
>> + * pgsize. This interface supports to get bitmap of smallest supported pgsize
>> + * only and can be modified in future to get bitmap of specified pgsize.
>> + * User must allocate memory for bitmap, zero the bitmap memory and set size
>> + * of allocated memory in bitmap_size field. One bit is used to represent one
>> + * page consecutively starting from iova offset. User should provide page size
>> + * in 'pgsize'. Bit set in bitmap indicates page at that offset from iova is
>> + * dirty. Caller must set argsz including size of structure
>> + * vfio_iommu_type1_dirty_bitmap_get.
> nit: ditto

I think this is still needed here because vfio_bitmap is only used in 
case of this particular flag.

Thanks,
Kirti

>> + *
>> + * Only one of the flags _START, STOP and _GET may be specified at a time.
>> + *
>> + */
>> +struct vfio_iommu_type1_dirty_bitmap {
>> +	__u32        argsz;
>> +	__u32        flags;
>> +#define VFIO_IOMMU_DIRTY_PAGES_FLAG_START	(1 << 0)
>> +#define VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP	(1 << 1)
>> +#define VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP	(1 << 2)
>> +	__u8         data[];
>> +};
>> +
>> +struct vfio_iommu_type1_dirty_bitmap_get {
>> +	__u64              iova;	/* IO virtual address */
>> +	__u64              size;	/* Size of iova range */
>> +	struct vfio_bitmap bitmap;
>> +};
>> +
>> +#define VFIO_IOMMU_DIRTY_PAGES             _IO(VFIO_TYPE, VFIO_BASE + 17)
>> +
>>   /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>>   
>>   /*
>>
> Thanks
> 
> Eric
> 


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-24 14:36                     ` Alex Williamson
@ 2020-03-24 20:23                       ` Dr. David Alan Gilbert
  2020-03-25  5:31                         ` Tian, Kevin
  0 siblings, 1 reply; 29+ messages in thread
From: Dr. David Alan Gilbert @ 2020-03-24 20:23 UTC (permalink / raw)
  To: Alex Williamson
  Cc: Zhengxiao.zx, Tian, Kevin, Liu, Yi L, cjia, kvm, eskultet, Yang,
	Ziye, cohuck, shuangtai.tst, qemu-devel, Wang, Zhi A, mlevitsk,
	pasic, aik, Kirti Wankhede, eauger, felipe, jonathan.davies,
	Yan Zhao, Liu, Changpeng, Ken.Xue

* Alex Williamson (alex.williamson@redhat.com) wrote:
> On Mon, 23 Mar 2020 23:01:18 -0400
> Yan Zhao <yan.y.zhao@intel.com> wrote:
> 
> > On Tue, Mar 24, 2020 at 02:51:14AM +0800, Dr. David Alan Gilbert wrote:
> > > * Alex Williamson (alex.williamson@redhat.com) wrote:  
> > > > On Mon, 23 Mar 2020 23:24:37 +0530
> > > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > >   
> > > > > On 3/21/2020 12:29 AM, Alex Williamson wrote:  
> > > > > > On Sat, 21 Mar 2020 00:12:04 +0530
> > > > > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > > >     
> > > > > >> On 3/20/2020 11:31 PM, Alex Williamson wrote:    
> > > > > >>> On Fri, 20 Mar 2020 23:19:14 +0530
> > > > > >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > > >>>        
> > > > > >>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:    
> > > > > >>>>> On Fri, 20 Mar 2020 01:46:41 +0530
> > > > > >>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > > >>>>>           
> > > > > >>
> > > > > >> <snip>
> > > > > >>    
> > > > > >>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> > > > > >>>>>> +				  size_t size, uint64_t pgsize,
> > > > > >>>>>> +				  u64 __user *bitmap)
> > > > > >>>>>> +{
> > > > > >>>>>> +	struct vfio_dma *dma;
> > > > > >>>>>> +	unsigned long pgshift = __ffs(pgsize);
> > > > > >>>>>> +	unsigned int npages, bitmap_size;
> > > > > >>>>>> +
> > > > > >>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
> > > > > >>>>>> +
> > > > > >>>>>> +	if (!dma)
> > > > > >>>>>> +		return -EINVAL;
> > > > > >>>>>> +
> > > > > >>>>>> +	if (dma->iova != iova || dma->size != size)
> > > > > >>>>>> +		return -EINVAL;
> > > > > >>>>>> +
> > > > > >>>>>> +	npages = dma->size >> pgshift;
> > > > > >>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> > > > > >>>>>> +
> > > > > >>>>>> +	/* mark all pages dirty if all pages are pinned and mapped. */
> > > > > >>>>>> +	if (dma->iommu_mapped)
> > > > > >>>>>> +		bitmap_set(dma->bitmap, 0, npages);
> > > > > >>>>>> +
> > > > > >>>>>> +	if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> > > > > >>>>>> +		return -EFAULT;    
> > > > > >>>>>
> > > > > >>>>> We still need to reset the bitmap here, clearing and re-adding the
> > > > > >>>>> pages that are still pinned.
> > > > > >>>>>
> > > > > >>>>> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> > > > > >>>>>           
> > > > > >>>>
> > > > > >>>> I thought you agreed on my reply to it
> > > > > >>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-f72b671fe703@nvidia.com/
> > > > > >>>>       
> > > > > >>>>    > Why re-populate when there will be no change since
> > > > > >>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If there is any
> > > > > >>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it will
> > > > > >>>>    > wait till iommu->lock is released. Bitmap will be populated when page is
> > > > > >>>>    > pinned.    
> > > > > >>>
> > > > > >>> As coded, dirty bits are only ever set in the bitmap, never cleared.
> > > > > >>> If a page is unpinned between iterations of the user recording the
> > > > > >>> dirty bitmap, it should be marked dirty in the iteration immediately
> > > > > >>> after the unpinning and not marked dirty in the following iteration.
> > > > > >>> That doesn't happen here.  We're reporting cumulative dirty pages since
> > > > > >>> logging was enabled, we need to be reporting dirty pages since the user
> > > > > >>> last retrieved the dirty bitmap.  The bitmap should be cleared and
> > > > > >>> currently pinned pages re-added after copying to the user.  Thanks,
> > > > > >>>        
> > > > > >>
> > > > > >> Does that mean, we have to track every iteration? do we really need that
> > > > > >> tracking?
> > > > > >>
> > > > > >> Generally the flow is:
> > > > > >> - vendor driver pin x pages
> > > > > >> - Enter pre-copy-phase where vCPUs are running - user starts dirty pages
> > > > > >> tracking, then user asks dirty bitmap, x pages reported dirty by
> > > > > >> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> > > > > >> - In pre-copy phase, vendor driver pins y more pages, now bitmap
> > > > > >> consists of x+y bits set
> > > > > >> - In pre-copy phase, vendor driver unpins z pages, but bitmap is not
> > > > > >> updated, so again bitmap consists of x+y bits set.
> > > > > >> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices are stopped
> > > > > >> - user asks dirty bitmap - Since here vCPU and mdev devices are stopped,
> > > > > >> pages should not get dirty by guest driver or the physical device.
> > > > > >> Hence, x+y dirty pages would be reported.
> > > > > >>
> > > > > >> I don't think we need to track every iteration of bitmap reporting.    
> > > > > > 
> > > > > > Yes, once a bitmap is read, it's reset.  In your example, after
> > > > > > unpinning z pages the user should still see a bitmap with x+y pages,
> > > > > > but once they've read that bitmap, the next bitmap should be x+y-z.
> > > > > > Userspace can make decisions about when to switch from pre-copy to
> > > > > > stop-and-copy based on convergence, ie. the slope of the line recording
> > > > > > dirty pages per iteration.  The implementation here never allows an
> > > > > > inflection point, dirty pages reported through vfio would always either
> > > > > > be flat or climbing.  There might also be a case that an iommu backed
> > > > > > device could start pinning pages during the course of a migration, how
> > > > > > would the bitmap ever revert from fully populated to only tracking the
> > > > > > pinned pages?  Thanks,
> > > > > >     
> > > > > 
> > > > > At KVM forum we discussed this - if guest driver pins say 1024 pages 
> > > > > before migration starts, during pre-copy phase device can dirty 0 pages 
> > > > > in best case and 1024 pages in worst case. In that case, user will 
> > > > > transfer content of 1024 pages during pre-copy phase and in 
> > > > > stop-and-copy phase also, that will be pages will be copied twice. So we 
> > > > > decided to only get dirty pages bitmap at stop-and-copy phase. If user 
> > > > > is going to get dirty pages in stop-and-copy phase only, then that will 
> > > > > be single iteration.
> > > > > There aren't any devices yet that can track sys memory dirty pages. So 
> > > > > we can go ahead with this patch and support for dirty pages tracking 
> > > > > during pre-copy phase can be added later when there will be consumers of 
> > > > > that functionality.  
> > > > 
> > > > So if I understand this right, you're expecting the dirty bitmap to
> > > > accumulate dirty bits, in perpetuity, so that the user can only
> > > > retrieve them once at the end of migration?  But if that's the case,
> > > > the user could simply choose to not retrieve the bitmap until the end
> > > > of migration, the result would be the same.  What we have here is that
> > > > dirty bits are never cleared, regardless of whether the user has seen
> > > > them, which is wrong.  Sorry, we had a lot of discussions at KVM forum,
> > > > I don't recall this specific one 5 months later and maybe we weren't
> > > > considering all aspects.  I see the behavior we have here as incorrect,
> > > > but it also seems relatively trivial to make correct.  I hope the QEMU
> > > > code isn't making us go through all this trouble to report a dirty
> > > > bitmap that gets thrown away because it expects the final one to be
> > > > cumulative since the beginning of dirty logging.  Thanks,  
> > > 
> > > I remember the discussion that we couldn't track the system memory
> > > dirtying with current hardware; so the question then is just to track  
> > hi Dave
> > there are already devices that are able to track the system memory,
> > through two ways:
> > (1) software method. like VFs for "Intel(R) Ethernet Controller XL710 Family
> > support".
> > (2) hardware method. through hardware internal buffer (as one Intel
> > internal hardware not yet to public, but very soon) or through VTD-3.0
> > IOMMU.
> > 
> > we have already had code verified using the two ways to track system memory
> > in fine-grained level.
> > 
> > 
> > > what has been pinned and then ideally put that memory off until the end.
> > > (Which is interesting because I don't think we currently have  a way
> > > to delay RAM pages till the end in qemu).  
> > 
> > I think the problem here is that we mixed pinned pages with dirty pages.
> 
> We are reporting dirty pages, pinned pages are just assumed to be dirty.
> 
> > yes, pinned pages for mdev devices are continuously likely to be dirty
> > until device stopped.
> > But for devices that are able to report dirty pages, dirtied pages
> > will be marked again if hardware writes them later.
> > 
> > So, is it good to introduce a capability to let vfio/qemu know how to
> > treat the dirty pages?
> 
> Dirty pages are dirty, QEMU doesn't need any special flag, instead we
> need to evolve different mechanisms for the vendor driver so that we
> can differentiate pages pinned for read vs pages pinned for write.
> Perhaps interfaces to pin pages without dirtying them, and a separate
> mechanism to dirty a previously pinned-page, ie. promote it permanently
> or transiently to a writable page.
> 
> > (1) for devices have no fine-grained dirty page tracking capability
> >   a. pinned pages are regarded as dirty pages. they are not cleared by
> >   dirty page query
> >   b. unpinned pages are regarded as dirty pages. they are cleared by
> >   dirty page query or UNMAP ioctl.
> > (2) for devices that have fine-grained dirty page tracking capability
> >    a. pinned/unpinned pages are not regarded as dirty pages
> 
> We need a pin-read-only interface for this.
> 
> >    b. only pages they reported are regarded as dirty pages and are to be
> >    cleared by dirty page query and UNMAP ioctl.
> 
> We need a set-dirty or promote-writable interface for this.
> 
> > (3) for dirty pages marking APIs, like vfio_dma_rw()...
> >    pages marked by them are regared as dirty and are to be cleared by
> >    dirty page query and UNMAP ioctl
> > 
> > For (1), qemu VFIO only reports dirty page amount and would not transfer
> > those pages until last round.
> > for (2) and (3), qemu VFIO should report and transfer them in each
> > round.
> 
> IMO, QEMU should not be aware of any of this.  Userspace has an
> interface to retrieve dirtied pages (period).  We should adjust the
> pages that we report as dirtied to be accurate based on the
> capabilities of the vendor driver.  We can evolve those internal APIs
> between the vendor driver and vfio iommu over time without modifying
> this user interface.

I'm not sure;  if you have a block of memory that's constantly marked
dirty in (1) - we need to avoid constantly retransmitting that memory to
the destination; there's no point in sending it until the end of the
iterations - so it shouldn't even get sent once in the iteration.
But at the same time, we can't ignore the fact that those pages are
going to be dirty - because that influences the downtime; so we need
to know we're going to be getting them later, even if we don't
initially mark them as dirty.

> > > [I still worry whether migration will be usable with any
> > > significant amount of system ram that's pinned in this way; the
> > > downside will very easily get above the threshold that people like]
> > >   
> > yes. that's why we have to do multi-round dirty page query and
> > transfer and clear the dirty bitmaps in each round for devices that are
> > able to track in fine grain.
> > and that's why we have to report the amount of dirty pages before
> > stop-and-copy phase for mdev devices, so that people are able to know
> > the real downtime as much as possible.
> 
> Yes, the dirty bitmap should be accurate to report the pages dirtied
> since it was last retrieved and over time we can add internal
> interfaces to give vendor drivers more granularity in marking pinned
> pages dirty and perhaps even exposing the bitmap to the vendor drivers
> to set pages themselves.  I don't necessarily think it's worthwhile to
> create a new class of dirtied pages to transfer at the end, we're
> fighting a losing battle at that point.  We should be focusing on
> improving the granularity of page dirtying in order to reduce the pages
> transferred at the end of migration.  Thanks,

Dave

> Alex
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK



^ permalink raw reply	[flat|nested] 29+ messages in thread

* RE: [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
  2020-03-24 20:23                       ` Dr. David Alan Gilbert
@ 2020-03-25  5:31                         ` Tian, Kevin
  0 siblings, 0 replies; 29+ messages in thread
From: Tian, Kevin @ 2020-03-25  5:31 UTC (permalink / raw)
  To: Dr. David Alan Gilbert, Alex Williamson
  Cc: Zhengxiao.zx, Liu, Yi L, cjia, kvm, eskultet, Yang, Ziye, cohuck,
	shuangtai.tst, qemu-devel, Wang,  Zhi A, mlevitsk, pasic, aik,
	Kirti Wankhede, eauger, felipe, jonathan.davies, Zhao, Yan Y,
	Liu, Changpeng, Ken.Xue

> From: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Sent: Wednesday, March 25, 2020 4:23 AM
> 
> * Alex Williamson (alex.williamson@redhat.com) wrote:
> > On Mon, 23 Mar 2020 23:01:18 -0400
> > Yan Zhao <yan.y.zhao@intel.com> wrote:
> >
> > > On Tue, Mar 24, 2020 at 02:51:14AM +0800, Dr. David Alan Gilbert wrote:
> > > > * Alex Williamson (alex.williamson@redhat.com) wrote:
> > > > > On Mon, 23 Mar 2020 23:24:37 +0530
> > > > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > >
> > > > > > On 3/21/2020 12:29 AM, Alex Williamson wrote:
> > > > > > > On Sat, 21 Mar 2020 00:12:04 +0530
> > > > > > > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > > > >
> > > > > > >> On 3/20/2020 11:31 PM, Alex Williamson wrote:
> > > > > > >>> On Fri, 20 Mar 2020 23:19:14 +0530
> > > > > > >>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > > > >>>
> > > > > > >>>> On 3/20/2020 4:27 AM, Alex Williamson wrote:
> > > > > > >>>>> On Fri, 20 Mar 2020 01:46:41 +0530
> > > > > > >>>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> > > > > > >>>>>
> > > > > > >>
> > > > > > >> <snip>
> > > > > > >>
> > > > > > >>>>>> +static int vfio_iova_dirty_bitmap(struct vfio_iommu
> *iommu, dma_addr_t iova,
> > > > > > >>>>>> +				  size_t size, uint64_t pgsize,
> > > > > > >>>>>> +				  u64 __user *bitmap)
> > > > > > >>>>>> +{
> > > > > > >>>>>> +	struct vfio_dma *dma;
> > > > > > >>>>>> +	unsigned long pgshift = __ffs(pgsize);
> > > > > > >>>>>> +	unsigned int npages, bitmap_size;
> > > > > > >>>>>> +
> > > > > > >>>>>> +	dma = vfio_find_dma(iommu, iova, 1);
> > > > > > >>>>>> +
> > > > > > >>>>>> +	if (!dma)
> > > > > > >>>>>> +		return -EINVAL;
> > > > > > >>>>>> +
> > > > > > >>>>>> +	if (dma->iova != iova || dma->size != size)
> > > > > > >>>>>> +		return -EINVAL;
> > > > > > >>>>>> +
> > > > > > >>>>>> +	npages = dma->size >> pgshift;
> > > > > > >>>>>> +	bitmap_size = DIRTY_BITMAP_BYTES(npages);
> > > > > > >>>>>> +
> > > > > > >>>>>> +	/* mark all pages dirty if all pages are pinned and
> mapped. */
> > > > > > >>>>>> +	if (dma->iommu_mapped)
> > > > > > >>>>>> +		bitmap_set(dma->bitmap, 0, npages);
> > > > > > >>>>>> +
> > > > > > >>>>>> +	if (copy_to_user((void __user *)bitmap, dma-
> >bitmap, bitmap_size))
> > > > > > >>>>>> +		return -EFAULT;
> > > > > > >>>>>
> > > > > > >>>>> We still need to reset the bitmap here, clearing and re-adding
> the
> > > > > > >>>>> pages that are still pinned.
> > > > > > >>>>>
> > > > > > >>>>>
> https://lore.kernel.org/kvm/20200319070635.2ff5db56@x1.home/
> > > > > > >>>>>
> > > > > > >>>>
> > > > > > >>>> I thought you agreed on my reply to it
> > > > > > >>>> https://lore.kernel.org/kvm/31621b70-02a9-2ea5-045f-
> f72b671fe703@nvidia.com/
> > > > > > >>>>
> > > > > > >>>>    > Why re-populate when there will be no change since
> > > > > > >>>>    > vfio_iova_dirty_bitmap() is called holding iommu->lock? If
> there is any
> > > > > > >>>>    > pin request while vfio_iova_dirty_bitmap() is still working, it
> will
> > > > > > >>>>    > wait till iommu->lock is released. Bitmap will be populated
> when page is
> > > > > > >>>>    > pinned.
> > > > > > >>>
> > > > > > >>> As coded, dirty bits are only ever set in the bitmap, never
> cleared.
> > > > > > >>> If a page is unpinned between iterations of the user recording
> the
> > > > > > >>> dirty bitmap, it should be marked dirty in the iteration
> immediately
> > > > > > >>> after the unpinning and not marked dirty in the following
> iteration.
> > > > > > >>> That doesn't happen here.  We're reporting cumulative dirty
> pages since
> > > > > > >>> logging was enabled, we need to be reporting dirty pages since
> the user
> > > > > > >>> last retrieved the dirty bitmap.  The bitmap should be cleared
> and
> > > > > > >>> currently pinned pages re-added after copying to the user.
> Thanks,
> > > > > > >>>
> > > > > > >>
> > > > > > >> Does that mean, we have to track every iteration? do we really
> need that
> > > > > > >> tracking?
> > > > > > >>
> > > > > > >> Generally the flow is:
> > > > > > >> - vendor driver pin x pages
> > > > > > >> - Enter pre-copy-phase where vCPUs are running - user starts
> dirty pages
> > > > > > >> tracking, then user asks dirty bitmap, x pages reported dirty by
> > > > > > >> VFIO_IOMMU_DIRTY_PAGES ioctl with _GET flag
> > > > > > >> - In pre-copy phase, vendor driver pins y more pages, now
> bitmap
> > > > > > >> consists of x+y bits set
> > > > > > >> - In pre-copy phase, vendor driver unpins z pages, but bitmap is
> not
> > > > > > >> updated, so again bitmap consists of x+y bits set.
> > > > > > >> - Enter in stop-and-copy phase, vCPUs are stopped, mdev devices
> are stopped
> > > > > > >> - user asks dirty bitmap - Since here vCPU and mdev devices are
> stopped,
> > > > > > >> pages should not get dirty by guest driver or the physical device.
> > > > > > >> Hence, x+y dirty pages would be reported.
> > > > > > >>
> > > > > > >> I don't think we need to track every iteration of bitmap reporting.
> > > > > > >
> > > > > > > Yes, once a bitmap is read, it's reset.  In your example, after
> > > > > > > unpinning z pages the user should still see a bitmap with x+y pages,
> > > > > > > but once they've read that bitmap, the next bitmap should be x+y-
> z.
> > > > > > > Userspace can make decisions about when to switch from pre-
> copy to
> > > > > > > stop-and-copy based on convergence, ie. the slope of the line
> recording
> > > > > > > dirty pages per iteration.  The implementation here never allows
> an
> > > > > > > inflection point, dirty pages reported through vfio would always
> either
> > > > > > > be flat or climbing.  There might also be a case that an iommu
> backed
> > > > > > > device could start pinning pages during the course of a migration,
> how
> > > > > > > would the bitmap ever revert from fully populated to only tracking
> the
> > > > > > > pinned pages?  Thanks,
> > > > > > >
> > > > > >
> > > > > > At KVM forum we discussed this - if guest driver pins say 1024 pages
> > > > > > before migration starts, during pre-copy phase device can dirty 0
> pages
> > > > > > in best case and 1024 pages in worst case. In that case, user will
> > > > > > transfer content of 1024 pages during pre-copy phase and in
> > > > > > stop-and-copy phase also, that will be pages will be copied twice. So
> we
> > > > > > decided to only get dirty pages bitmap at stop-and-copy phase. If
> user
> > > > > > is going to get dirty pages in stop-and-copy phase only, then that will
> > > > > > be single iteration.
> > > > > > There aren't any devices yet that can track sys memory dirty pages.
> So
> > > > > > we can go ahead with this patch and support for dirty pages tracking
> > > > > > during pre-copy phase can be added later when there will be
> consumers of
> > > > > > that functionality.
> > > > >
> > > > > So if I understand this right, you're expecting the dirty bitmap to
> > > > > accumulate dirty bits, in perpetuity, so that the user can only
> > > > > retrieve them once at the end of migration?  But if that's the case,
> > > > > the user could simply choose to not retrieve the bitmap until the end
> > > > > of migration, the result would be the same.  What we have here is
> that
> > > > > dirty bits are never cleared, regardless of whether the user has seen
> > > > > them, which is wrong.  Sorry, we had a lot of discussions at KVM
> forum,
> > > > > I don't recall this specific one 5 months later and maybe we weren't
> > > > > considering all aspects.  I see the behavior we have here as incorrect,
> > > > > but it also seems relatively trivial to make correct.  I hope the QEMU
> > > > > code isn't making us go through all this trouble to report a dirty
> > > > > bitmap that gets thrown away because it expects the final one to be
> > > > > cumulative since the beginning of dirty logging.  Thanks,
> > > >
> > > > I remember the discussion that we couldn't track the system memory
> > > > dirtying with current hardware; so the question then is just to track
> > > hi Dave
> > > there are already devices that are able to track the system memory,
> > > through two ways:
> > > (1) software method. like VFs for "Intel(R) Ethernet Controller XL710
> Family
> > > support".
> > > (2) hardware method. through hardware internal buffer (as one Intel
> > > internal hardware not yet to public, but very soon) or through VTD-3.0
> > > IOMMU.
> > >
> > > we have already had code verified using the two ways to track system
> memory
> > > in fine-grained level.
> > >
> > >
> > > > what has been pinned and then ideally put that memory off until the
> end.
> > > > (Which is interesting because I don't think we currently have  a way
> > > > to delay RAM pages till the end in qemu).
> > >
> > > I think the problem here is that we mixed pinned pages with dirty pages.
> >
> > We are reporting dirty pages, pinned pages are just assumed to be dirty.
> >
> > > yes, pinned pages for mdev devices are continuously likely to be dirty
> > > until device stopped.
> > > But for devices that are able to report dirty pages, dirtied pages
> > > will be marked again if hardware writes them later.
> > >
> > > So, is it good to introduce a capability to let vfio/qemu know how to
> > > treat the dirty pages?
> >
> > Dirty pages are dirty, QEMU doesn't need any special flag, instead we
> > need to evolve different mechanisms for the vendor driver so that we
> > can differentiate pages pinned for read vs pages pinned for write.
> > Perhaps interfaces to pin pages without dirtying them, and a separate
> > mechanism to dirty a previously pinned-page, ie. promote it permanently
> > or transiently to a writable page.
> >
> > > (1) for devices have no fine-grained dirty page tracking capability
> > >   a. pinned pages are regarded as dirty pages. they are not cleared by
> > >   dirty page query
> > >   b. unpinned pages are regarded as dirty pages. they are cleared by
> > >   dirty page query or UNMAP ioctl.
> > > (2) for devices that have fine-grained dirty page tracking capability
> > >    a. pinned/unpinned pages are not regarded as dirty pages
> >
> > We need a pin-read-only interface for this.
> >
> > >    b. only pages they reported are regarded as dirty pages and are to be
> > >    cleared by dirty page query and UNMAP ioctl.
> >
> > We need a set-dirty or promote-writable interface for this.
> >
> > > (3) for dirty pages marking APIs, like vfio_dma_rw()...
> > >    pages marked by them are regared as dirty and are to be cleared by
> > >    dirty page query and UNMAP ioctl
> > >
> > > For (1), qemu VFIO only reports dirty page amount and would not
> transfer
> > > those pages until last round.
> > > for (2) and (3), qemu VFIO should report and transfer them in each
> > > round.
> >
> > IMO, QEMU should not be aware of any of this.  Userspace has an
> > interface to retrieve dirtied pages (period).  We should adjust the
> > pages that we report as dirtied to be accurate based on the
> > capabilities of the vendor driver.  We can evolve those internal APIs
> > between the vendor driver and vfio iommu over time without modifying
> > this user interface.
> 
> I'm not sure;  if you have a block of memory that's constantly marked
> dirty in (1) - we need to avoid constantly retransmitting that memory to
> the destination; there's no point in sending it until the end of the
> iterations - so it shouldn't even get sent once in the iteration.
> But at the same time, we can't ignore the fact that those pages are
> going to be dirty - because that influences the downtime; so we need
> to know we're going to be getting them later, even if we don't
> initially mark them as dirty.

For that we possibly need a way to allow VFIO or vendor driver telling
the userspace that I can report dirty pages to you but it is better to do
it in the end since the set is sort of static and big thus not optimal to
transfer them multiple rounds, and I can also report to you the number 
of currently-tracked dirty pages so you may use it to make accurate
prediction to decide when to exit the precopy. But such feature might
be introduced orthogonal to the standard bitmap interface, i.e. not
necessarily to block this series for the baseline live migration support...

Thanks
Kevin

> 
> > > > [I still worry whether migration will be usable with any
> > > > significant amount of system ram that's pinned in this way; the
> > > > downside will very easily get above the threshold that people like]
> > > >
> > > yes. that's why we have to do multi-round dirty page query and
> > > transfer and clear the dirty bitmaps in each round for devices that are
> > > able to track in fine grain.
> > > and that's why we have to report the amount of dirty pages before
> > > stop-and-copy phase for mdev devices, so that people are able to know
> > > the real downtime as much as possible.
> >
> > Yes, the dirty bitmap should be accurate to report the pages dirtied
> > since it was last retrieved and over time we can add internal
> > interfaces to give vendor drivers more granularity in marking pinned
> > pages dirty and perhaps even exposing the bitmap to the vendor drivers
> > to set pages themselves.  I don't necessarily think it's worthwhile to
> > create a new class of dirtied pages to transfer at the end, we're
> > fighting a losing battle at that point.  We should be focusing on
> > improving the granularity of page dirtying in order to reduce the pages
> > transferred at the end of migration.  Thanks,
> 
> Dave
> 
> > Alex
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK



^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state
  2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
  2020-03-23 20:30   ` Auger Eric
@ 2020-03-26  9:33   ` Christoph Hellwig
  2020-03-26 21:39     ` Kirti Wankhede
  1 sibling, 1 reply; 29+ messages in thread
From: Christoph Hellwig @ 2020-03-26  9:33 UTC (permalink / raw)
  To: Kirti Wankhede
  Cc: cjia, kvm, aik, Zhengxiao.zx, shuangtai.tst, qemu-devel, eauger,
	yi.l.liu, eskultet, ziye.yang, mlevitsk, pasic, felipe,
	zhi.a.wang, kevin.tian, yan.y.zhao, dgilbert, alex.williamson,
	changpeng.liu, cohuck, Ken.Xue, jonathan.davies

s/KABI/UAPI/ in the subject and anywhere else in the series.

Please avoid __packed__ structures and just properly pad them, they
have a major performance impact on some platforms and will cause
compiler warnings when taking addresses of members.


^ permalink raw reply	[flat|nested] 29+ messages in thread

* Re: [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state
  2020-03-26  9:33   ` Christoph Hellwig
@ 2020-03-26 21:39     ` Kirti Wankhede
  0 siblings, 0 replies; 29+ messages in thread
From: Kirti Wankhede @ 2020-03-26 21:39 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: cjia, kvm, aik, Zhengxiao.zx, shuangtai.tst, qemu-devel, eauger,
	yi.l.liu, eskultet, ziye.yang, mlevitsk, pasic, felipe,
	zhi.a.wang, kevin.tian, yan.y.zhao, dgilbert, alex.williamson,
	changpeng.liu, cohuck, Ken.Xue, jonathan.davies



On 3/26/2020 3:03 PM, Christoph Hellwig wrote:
> s/KABI/UAPI/ in the subject and anywhere else in the series.
> 

Ok.

> Please avoid __packed__ structures and just properly pad them, they
> have a major performance impact on some platforms and will cause
> compiler warnings when taking addresses of members.
> 

Yes, removing it.

Thanks,
Kirti


^ permalink raw reply	[flat|nested] 29+ messages in thread

end of thread, back to index

Thread overview: 29+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
2020-03-23 20:30   ` Auger Eric
2020-03-24 19:31     ` Kirti Wankhede
2020-03-26  9:33   ` Christoph Hellwig
2020-03-26 21:39     ` Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Kirti Wankhede
2020-03-23 20:30   ` Auger Eric
2020-03-24 19:34     ` Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
2020-03-23 21:11   ` Auger Eric
2020-03-24 19:49     ` Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
2020-03-19 22:57   ` Alex Williamson
2020-03-20 17:49     ` Kirti Wankhede
2020-03-20 18:01       ` Alex Williamson
2020-03-20 18:42         ` Kirti Wankhede
2020-03-20 18:59           ` Alex Williamson
2020-03-23 17:54             ` Kirti Wankhede
2020-03-23 18:44               ` Alex Williamson
2020-03-23 18:51                 ` Dr. David Alan Gilbert
2020-03-24  3:01                   ` Yan Zhao
2020-03-24  9:45                     ` Kirti Wankhede
2020-03-24 14:36                     ` Alex Williamson
2020-03-24 20:23                       ` Dr. David Alan Gilbert
2020-03-25  5:31                         ` Tian, Kevin
2020-03-19 20:16 ` [PATCH v15 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages Kirti Wankhede

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