* [PATCH v1 0/9] virtio-mem: vfio support
@ 2020-11-19 15:39 David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions David Hildenbrand
` (9 more replies)
0 siblings, 10 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr. David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Paolo Bonzini, Igor Mammedov,
Marek Kedzierski
This is the follow-up of:
https://lkml.kernel.org/r/20200924160423.106747-1-david@redhat.com
to make vfio and virtio-mem play together. The basic idea was the result of
Alex brainstorming with me on how to tackle this.
A virtio-mem device manages a memory region in guest physical address
space, represented as a single (currently large) memory region in QEMU,
mapped into system memory address space. Before the guest is allowed to use
memory blocks, it must coordinate with the hypervisor (plug blocks). After
a reboot, all memory is usually unplugged - when the guest comes up, it
detects the virtio-mem device and selects memory blocks to plug (based on
resize requests from the hypervisor).
Memory hot(un)plug consists of (un)plugging memory blocks via a virtio-mem
device (triggered by the guest). When unplugging blocks, we discard the
memory - similar to memory balloon inflation. In contrast to memory
ballooning, we always know which memory blocks a guest may actually use -
especially during a reboot, after a crash, or after kexec (and during
hibernation as well). Guests agreed to no access unplugged memory again,
especially not via DMA.
The issue with vfio is, that it cannot deal with random discards - for this
reason, virtio-mem and vfio can currently only run mutually exclusive.
Especially, vfio would currently map the whole memory region (with possible
only little/no plugged blocks), resulting in all pages getting pinned and
therefore resulting in a higher memory consumption than expected (turning
virtio-mem basically useless in these environments).
To make vfio work nicely with virtio-mem, we have to map only the plugged
blocks, and map/unmap properly when plugging/unplugging blocks (including
discarding of RAM when unplugging). We achieve that by using a new notifier
mechanism that communicates changes.
It's important to map memory in the granularity in which we could see
unmaps again (-> virtio-mem block size) - so when e.g., plugging
consecutive 100 MB with a block size of 2MB, we need 50 mappings. When
unmapping, we can use a single vfio_unmap call for the applicable range.
We expect that the block size of virtio-mem devices will be fairly large
in the future (to not run out of mappings and to improve hot(un)plug
performance), configured by the user, when used with vfio (e.g., 128MB,
1G, ...).
More info regarding virtio-mem can be found at:
https://virtio-mem.gitlab.io/
I'll add a guide for virtio-mem+vfio soonish.
v1 is located at:
git@github.com:davidhildenbrand/qemu.git virtio-mem-vfio-v1
RFC - v1:
- VFIO migration code. Due to missing kernel support, I cannot really test
if that part works.
- Understand/test/document vIOMMU implications, also regarding migration
- Nicer ram_block_discard_disable/require handling.
- s/SparseRAMHandler/RamDiscardMgr/, refactorings, cleanups, documentation,
testing, ...
David Hildenbrand (9):
memory: Introduce RamDiscardMgr for RAM memory regions
virtio-mem: Factor out traversing unplugged ranges
virtio-mem: Implement RamDiscardMgr interface
vfio: Support for RamDiscardMgr in the !vIOMMU case
vfio: Support for RamDiscardMgr in the vIOMMU case
softmmu/physmem: Don't use atomic operations in
ram_block_discard_(disable|require)
softmmu/physmem: Extend ram_block_discard_(require|disable) by two
discard types
virtio-mem: Require only coordinated discards
vfio: Disable only uncoordinated discards
hw/vfio/common.c | 282 ++++++++++++++++++++++++++++-
hw/virtio/virtio-mem.c | 319 ++++++++++++++++++++++++++++-----
include/exec/memory.h | 243 ++++++++++++++++++++++++-
include/hw/vfio/vfio-common.h | 12 ++
include/hw/virtio/virtio-mem.h | 3 +
softmmu/memory.c | 22 +++
softmmu/physmem.c | 108 ++++++++---
7 files changed, 913 insertions(+), 76 deletions(-)
--
2.26.2
^ permalink raw reply [flat|nested] 17+ messages in thread
* [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-12-02 23:26 ` Alex Williamson
2020-11-19 15:39 ` [PATCH v1 2/9] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
` (8 subsequent siblings)
9 siblings, 1 reply; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
We have some special RAM memory regions (managed by virtio-mem), whereby
the guest agreed to only use selected memory ranges. "unused" parts are
discarded so they won't consume memory - to logically unplug these memory
ranges. Before the VM is allowed to use such logically unplugged memory
again, coordination with the hypervisor is required.
This results in "sparse" mmaps/RAMBlocks/memory regions, whereby only
coordinated parts are valid to be used/accessed by the VM.
In most cases, we don't care about that - e.g., in KVM, we simply have a
single KVM memory slot. However, in case of vfio, registering the
whole region with the kernel results in all pages getting pinned, and
therefore an unexpected high memory consumption - discarding of RAM in
that context is broken.
Let's introduce a way to coordinate discarding/populating memory within a
RAM memory region with such special consumers of RAM memory regions: they
can register as listeners and get updates on memory getting discarded and
populated. Using this machinery, vfio will be able to map only the
currently populated parts, resulting in discarded parts not getting pinned
and not consuming memory.
A RamDiscardMgr has to be set for a memory region before it is getting
mapped, and cannot change while the memory region is mapped.
Note: At some point, we might want to let RAMBlock users (esp. vfio used
for nvme://) consume this interface as well. We'll need RAMBlock notifier
calls when a RAMBlock is getting mapped/unmapped (via the corresponding
memory region), so we can properly register a listener there as well.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/exec/memory.h | 225 ++++++++++++++++++++++++++++++++++++++++++
softmmu/memory.c | 22 +++++
2 files changed, 247 insertions(+)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 0f3e6bcd5e..468cbb53a4 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -42,6 +42,12 @@ typedef struct IOMMUMemoryRegionClass IOMMUMemoryRegionClass;
DECLARE_OBJ_CHECKERS(IOMMUMemoryRegion, IOMMUMemoryRegionClass,
IOMMU_MEMORY_REGION, TYPE_IOMMU_MEMORY_REGION)
+#define TYPE_RAM_DISCARD_MGR "qemu:ram-discard-mgr"
+typedef struct RamDiscardMgrClass RamDiscardMgrClass;
+typedef struct RamDiscardMgr RamDiscardMgr;
+DECLARE_OBJ_CHECKERS(RamDiscardMgr, RamDiscardMgrClass, RAM_DISCARD_MGR,
+ TYPE_RAM_DISCARD_MGR);
+
#ifdef CONFIG_FUZZ
void fuzz_dma_read_cb(size_t addr,
size_t len,
@@ -116,6 +122,66 @@ struct IOMMUNotifier {
};
typedef struct IOMMUNotifier IOMMUNotifier;
+struct RamDiscardListener;
+typedef int (*NotifyRamPopulate)(struct RamDiscardListener *rdl,
+ const MemoryRegion *mr, ram_addr_t offset,
+ ram_addr_t size);
+typedef void (*NotifyRamDiscard)(struct RamDiscardListener *rdl,
+ const MemoryRegion *mr, ram_addr_t offset,
+ ram_addr_t size);
+typedef void (*NotifyRamDiscardAll)(struct RamDiscardListener *rdl,
+ const MemoryRegion *mr);
+
+typedef struct RamDiscardListener {
+ /*
+ * @notify_populate:
+ *
+ * Notification that previously discarded memory is about to get populated.
+ * Listeners are able to object. If any listener objects, already
+ * successfully notified listeners are notified about a discard again.
+ *
+ * @rdl: the #RamDiscardListener getting notified
+ * @mr: the relevant #MemoryRegion
+ * @offset: offset into the #MemoryRegion, aligned to minimum granularity of
+ * the #RamDiscardMgr
+ * @size: the size, aligned to minimum granularity of the #RamDiscardMgr
+ *
+ * Returns 0 on success. If the notification is rejected by the listener,
+ * an error is returned.
+ */
+ NotifyRamPopulate notify_populate;
+
+ /*
+ * @notify_discard:
+ *
+ * Notification that previously populated memory was discarded successfully
+ * and listeners should drop all references to such memory and prevent
+ * new population (e.g., unmap).
+ *
+ * @rdl: the #RamDiscardListener getting notified
+ * @mr: the relevant #MemoryRegion
+ * @offset: offset into the #MemoryRegion, aligned to minimum granularity of
+ * the #RamDiscardMgr
+ * @size: the size, aligned to minimum granularity of the #RamDiscardMgr
+ */
+ NotifyRamDiscard notify_discard;
+
+ /*
+ * @notify_discard_all:
+ *
+ * Notification that all previously populated memory was discarded
+ * successfully.
+ *
+ * Note: this callback is optional. If not set, individual notify_populate()
+ * notifications are triggered.
+ *
+ * @rdl: the #RamDiscardListener getting notified
+ * @mr: the relevant #MemoryRegion
+ */
+ NotifyRamDiscardAll notify_discard_all;
+ QLIST_ENTRY(RamDiscardListener) next;
+} RamDiscardListener;
+
/* RAM is pre-allocated and passed into qemu_ram_alloc_from_ptr */
#define RAM_PREALLOC (1 << 0)
@@ -151,6 +217,16 @@ static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
n->iommu_idx = iommu_idx;
}
+static inline void ram_discard_listener_init(RamDiscardListener *rdl,
+ NotifyRamPopulate populate_fn,
+ NotifyRamDiscard discard_fn,
+ NotifyRamDiscardAll discard_all_fn)
+{
+ rdl->notify_populate = populate_fn;
+ rdl->notify_discard = discard_fn;
+ rdl->notify_discard_all = discard_all_fn;
+}
+
/*
* Memory region callbacks
*/
@@ -425,6 +501,120 @@ struct IOMMUMemoryRegionClass {
Error **errp);
};
+/*
+ * RamDiscardMgrClass:
+ *
+ * A #RamDiscardMgr coordinates which parts of specific RAM #MemoryRegion
+ * regions are currently populated to be used/accessed by the VM, notifying
+ * after parts were discarded (freeing up memory) and before parts will be
+ * populated (consuming memory), to be used/acessed by the VM.
+ *
+ * A #RamDiscardMgr can only be set for a RAM #MemoryRegion while the
+ * #MemoryRegion isn't mapped yet; it cannot change while the #MemoryRegion is
+ * mapped.
+ *
+ * The #RamDiscardMgr is intended to be used by technologies that are
+ * incompatible with discarding of RAM (e.g., VFIO, which may pin all
+ * memory inside a #MemoryRegion), and require proper coordination to only
+ * map the currently populated parts, to hinder parts that are expected to
+ * remain discarded from silently getting populated and consuming memory.
+ * Technologies that support discarding of RAM don't have to bother and can
+ * simply map the whole #MemoryRegion.
+ *
+ * An example #RamDiscardMgr is virtio-mem, which logically (un)plugs
+ * memory within an assigned RAM #MemoryRegion, coordinated with the VM.
+ * Logically unplugging memory consists of discarding RAM. The VM agreed to not
+ * access unplugged (discarded) memory - especially via DMA. virtio-mem will
+ * properly coordinate with listeners before memory is plugged (populated),
+ * and after memory is unplugged (discarded).
+ *
+ * Listeners are called in multiples of the minimum granularity and changes are
+ * aligned to the minimum granularity within the #MemoryRegion. Listeners have
+ * to prepare for memory becomming discarded in a different granularity than it
+ * was populated and the other way around.
+ */
+struct RamDiscardMgrClass {
+ /* private */
+ InterfaceClass parent_class;
+
+ /* public */
+
+ /**
+ * @get_min_granularity:
+ *
+ * Get the minimum granularity in which listeners will get notified
+ * about changes within the #MemoryRegion via the #RamDiscardMgr.
+ *
+ * @rdm: the #RamDiscardMgr
+ * @mr: the #MemoryRegion
+ *
+ * Returns the minimum granularity.
+ */
+ uint64_t (*get_min_granularity)(const RamDiscardMgr *rdm,
+ const MemoryRegion *mr);
+
+ /**
+ * @is_populated:
+ *
+ * Check whether the given range within the #MemoryRegion is completely
+ * populated (i.e., no parts are currently discarded). There are no
+ * alignment requirements for the range.
+ *
+ * @rdm: the #RamDiscardMgr
+ * @mr: the #MemoryRegion
+ * @offset: offset into the #MemoryRegion
+ * @size: size in the #MemoryRegion
+ *
+ * Returns the minimum granularity.
+ */
+ bool (*is_populated)(const RamDiscardMgr *rdm, const MemoryRegion *mr,
+ ram_addr_t start, ram_addr_t offset);
+
+ /**
+ * @register_listener:
+ *
+ * Register a #RamDiscardListener for a #MemoryRegion via the
+ * #RamDiscardMgr.
+ *
+ * @rdm: the #RamDiscardMgr
+ * @mr: the #MemoryRegion
+ * @rdl: the #RamDiscardListener
+ */
+ void (*register_listener)(RamDiscardMgr *rdm, const MemoryRegion *mr,
+ RamDiscardListener *rdl);
+
+ /**
+ * @unregister_listener:
+ *
+ * Unregister a previously registered #RamDiscardListener for a
+ * #MemoryRegion via the #RamDiscardMgr.
+ *
+ * @rdm: the #RamDiscardMgr
+ * @mr: the #MemoryRegion
+ * @rdl: the #RamDiscardListener
+ */
+ void (*unregister_listener)(RamDiscardMgr *rdm, const MemoryRegion *mr,
+ RamDiscardListener *rdl);
+
+ /**
+ * @replay_populated:
+ *
+ * Notify the #RamDiscardListener about all populated parts within the
+ * #MemoryRegion via the #RamDiscardMgr
+ *
+ * In case any notification fails, no further notifications are triggered.
+ * The listener is not required to be registered.
+ *
+ * @rdm: the #RamDiscardMgr
+ * @mr: the #MemoryRegion
+ * @rdl: the #RamDiscardListener
+ *
+ * Returns 0 on success, or a negative error if any notification failed.
+ */
+ int (*replay_populated)(const RamDiscardMgr *rdm, const MemoryRegion *mr,
+ RamDiscardListener *rdl);
+};
+
typedef struct CoalescedMemoryRange CoalescedMemoryRange;
typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
@@ -471,6 +661,7 @@ struct MemoryRegion {
const char *name;
unsigned ioeventfd_nb;
MemoryRegionIoeventfd *ioeventfds;
+ RamDiscardMgr *rdm; /* Only for RAM */
};
struct IOMMUMemoryRegion {
@@ -1965,6 +2156,40 @@ bool memory_region_present(MemoryRegion *container, hwaddr addr);
*/
bool memory_region_is_mapped(MemoryRegion *mr);
+/**
+ * memory_region_get_ram_discard_mgr: get the #RamDiscardMgr for a
+ * #MemoryRegion
+ *
+ * The #RamDiscardMgr cannot change while a memory region is mapped.
+ *
+ * @mr: the #MemoryRegion
+ */
+RamDiscardMgr *memory_region_get_ram_discard_mgr(MemoryRegion *mr);
+
+/**
+ * memory_region_has_ram_discard_mgr: check whether a #MemoryRegion has a
+ * #RamDiscardMgr assigned
+ *
+ * @mr: the #MemoryRegion
+ */
+static inline bool memory_region_has_ram_discard_mgr(MemoryRegion *mr)
+{
+ return !!memory_region_get_ram_discard_mgr(mr);
+}
+
+/**
+ * memory_region_set_ram_discard_mgr: set the #RamDiscardMgr for a
+ * #MemoryRegion
+ *
+ * This function must not be called for a mapped #MemoryRegion, a #MemoryRegion
+ * that does not cover RAM, or a #MemoryRegion that already has a
+ * #RamDiscardMgr assigned.
+ *
+ * @mr: the #MemoryRegion
+ * @urn: #RamDiscardMgr to set
+ */
+void memory_region_set_ram_discard_mgr(MemoryRegion *mr, RamDiscardMgr *rdm);
+
/**
* memory_region_find: translate an address/size relative to a
* MemoryRegion into a #MemoryRegionSection.
diff --git a/softmmu/memory.c b/softmmu/memory.c
index aa393f1bb0..fbdc50fa8b 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2013,6 +2013,21 @@ int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr)
return imrc->num_indexes(iommu_mr);
}
+RamDiscardMgr *memory_region_get_ram_discard_mgr(MemoryRegion *mr)
+{
+ if (!memory_region_is_mapped(mr) || !memory_region_is_ram(mr)) {
+ return false;
+ }
+ return mr->rdm;
+}
+
+void memory_region_set_ram_discard_mgr(MemoryRegion *mr, RamDiscardMgr *rdm)
+{
+ g_assert(memory_region_is_ram(mr) && !memory_region_is_mapped(mr));
+ g_assert(!rdm || !mr->rdm);
+ mr->rdm = rdm;
+}
+
void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
{
uint8_t mask = 1 << client;
@@ -3294,10 +3309,17 @@ static const TypeInfo iommu_memory_region_info = {
.abstract = true,
};
+static const TypeInfo ram_discard_mgr_info = {
+ .parent = TYPE_INTERFACE,
+ .name = TYPE_RAM_DISCARD_MGR,
+ .class_size = sizeof(RamDiscardMgrClass),
+};
+
static void memory_register_types(void)
{
type_register_static(&memory_region_info);
type_register_static(&iommu_memory_region_info);
+ type_register_static(&ram_discard_mgr_info);
}
type_init(memory_register_types)
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 2/9] virtio-mem: Factor out traversing unplugged ranges
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 3/9] virtio-mem: Implement RamDiscardMgr interface David Hildenbrand
` (7 subsequent siblings)
9 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
Let's factor out the core logic, to be reused soon.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/virtio-mem.c | 86 ++++++++++++++++++++++++------------------
1 file changed, 49 insertions(+), 37 deletions(-)
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 655824ff81..471e464171 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -145,6 +145,33 @@ static bool virtio_mem_is_busy(void)
return migration_in_incoming_postcopy() || !migration_is_idle();
}
+typedef int (*virtio_mem_range_cb)(const VirtIOMEM *vmem, void *arg,
+ uint64_t offset, uint64_t size);
+
+static int virtio_mem_for_each_unplugged_range(const VirtIOMEM *vmem, void *arg,
+ virtio_mem_range_cb cb)
+{
+ unsigned long first_zero_bit, last_zero_bit;
+ uint64_t offset, size;
+ int ret = 0;
+
+ first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
+ while (first_zero_bit < vmem->bitmap_size) {
+ offset = first_zero_bit * vmem->block_size;
+ last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
+ first_zero_bit + 1) - 1;
+ size = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
+
+ ret = cb(vmem, arg, offset, size);
+ if (ret) {
+ break;
+ }
+ first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
+ last_zero_bit + 2);
+ }
+ return ret;
+}
+
static bool virtio_mem_test_bitmap(VirtIOMEM *vmem, uint64_t start_gpa,
uint64_t size, bool plugged)
{
@@ -594,33 +621,27 @@ static void virtio_mem_device_unrealize(DeviceState *dev)
ram_block_discard_require(false);
}
-static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
+static int virtio_mem_discard_range_cb(const VirtIOMEM *vmem, void *arg,
+ uint64_t offset, uint64_t size)
{
RAMBlock *rb = vmem->memdev->mr.ram_block;
- unsigned long first_zero_bit, last_zero_bit;
- uint64_t offset, length;
int ret;
- /* Find consecutive unplugged blocks and discard the consecutive range. */
- first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
- while (first_zero_bit < vmem->bitmap_size) {
- offset = first_zero_bit * vmem->block_size;
- last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
- first_zero_bit + 1) - 1;
- length = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
-
- ret = ram_block_discard_range(rb, offset, length);
- if (ret) {
- error_report("Unexpected error discarding RAM: %s",
- strerror(-ret));
- return -EINVAL;
- }
- first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
- last_zero_bit + 2);
+ ret = ram_block_discard_range(rb, offset, size);
+ if (ret) {
+ error_report("Unexpected error discarding RAM: %s", strerror(-ret));
+ return -EINVAL;
}
return 0;
}
+static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
+{
+ /* Make sure all memory is really discarded after migration. */
+ return virtio_mem_for_each_unplugged_range(vmem, NULL,
+ virtio_mem_discard_range_cb);
+}
+
static int virtio_mem_post_load(void *opaque, int version_id)
{
if (migration_in_incoming_postcopy()) {
@@ -872,28 +893,19 @@ static void virtio_mem_set_block_size(Object *obj, Visitor *v, const char *name,
vmem->block_size = value;
}
-static void virtio_mem_precopy_exclude_unplugged(VirtIOMEM *vmem)
+static int virtio_mem_precopy_exclude_range_cb(const VirtIOMEM *vmem, void *arg,
+ uint64_t offset, uint64_t size)
{
void * const host = qemu_ram_get_host_addr(vmem->memdev->mr.ram_block);
- unsigned long first_zero_bit, last_zero_bit;
- uint64_t offset, length;
- /*
- * Find consecutive unplugged blocks and exclude them from migration.
- *
- * Note: Blocks cannot get (un)plugged during precopy, no locking needed.
- */
- first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
- while (first_zero_bit < vmem->bitmap_size) {
- offset = first_zero_bit * vmem->block_size;
- last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
- first_zero_bit + 1) - 1;
- length = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
+ qemu_guest_free_page_hint(host + offset, size);
+ return 0;
+}
- qemu_guest_free_page_hint(host + offset, length);
- first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
- last_zero_bit + 2);
- }
+static void virtio_mem_precopy_exclude_unplugged(VirtIOMEM *vmem)
+{
+ virtio_mem_for_each_unplugged_range(vmem, NULL,
+ virtio_mem_precopy_exclude_range_cb);
}
static int virtio_mem_precopy_notify(NotifierWithReturn *n, void *data)
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 3/9] virtio-mem: Implement RamDiscardMgr interface
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 2/9] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case David Hildenbrand
` (6 subsequent siblings)
9 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
Let's properly notify when (un)plugging blocks, after discarding memory
and before allowing the guest to consume memory. Handle errors from
notifiers gracefully (e.g., no remaining VFIO mappings) when plugging,
rolling back the change and telling the guest that the VM is busy.
One special case to take care of is replaying all notifications after
restoring the vmstate. The device starts out with all memory discarded,
so after loading the vmstate, we have to notify about all plugged
blocks.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/virtio-mem.c | 231 ++++++++++++++++++++++++++++++++-
include/hw/virtio/virtio-mem.h | 3 +
2 files changed, 231 insertions(+), 3 deletions(-)
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 471e464171..93257b6c26 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -172,7 +172,110 @@ static int virtio_mem_for_each_unplugged_range(const VirtIOMEM *vmem, void *arg,
return ret;
}
-static bool virtio_mem_test_bitmap(VirtIOMEM *vmem, uint64_t start_gpa,
+static int virtio_mem_for_each_plugged_range(const VirtIOMEM *vmem, void *arg,
+ virtio_mem_range_cb cb)
+{
+ unsigned long first_bit, last_bit;
+ uint64_t offset, size;
+ int ret = 0;
+
+ first_bit = find_first_bit(vmem->bitmap, vmem->bitmap_size);
+ while (first_bit < vmem->bitmap_size) {
+ offset = first_bit * vmem->block_size;
+ last_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
+ first_bit + 1) - 1;
+ size = (last_bit - first_bit + 1) * vmem->block_size;
+
+ ret = cb(vmem, arg, offset, size);
+ if (ret) {
+ break;
+ }
+ first_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
+ last_bit + 2);
+ }
+ return ret;
+}
+
+static void virtio_mem_notify_unplug(VirtIOMEM *vmem, uint64_t offset,
+ uint64_t size)
+{
+ RamDiscardListener *rdl;
+
+ QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+ rdl->notify_discard(rdl, &vmem->memdev->mr, offset, size);
+ }
+}
+
+static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
+ uint64_t size)
+{
+ RamDiscardListener *rdl, *rdl2;
+ int ret = 0, ret2;
+
+ QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+ ret = rdl->notify_populate(rdl, &vmem->memdev->mr, offset, size);
+ if (ret) {
+ break;
+ }
+ }
+
+ if (ret) {
+ /* Could be a mapping attempt resulted in memory getting populated. */
+ ret2 = ram_block_discard_range(vmem->memdev->mr.ram_block, offset,
+ size);
+ if (ret2) {
+ error_report("Unexpected error discarding RAM: %s",
+ strerror(-ret2));
+ }
+
+ /* Notify all already-notified listeners. */
+ QLIST_FOREACH(rdl2, &vmem->rdl_list, next) {
+ if (rdl2 == rdl) {
+ break;
+ }
+ rdl2->notify_discard(rdl2, &vmem->memdev->mr, offset, size);
+ }
+ }
+ return ret;
+}
+
+static int virtio_mem_notify_discard_range_cb(const VirtIOMEM *vmem, void *arg,
+ uint64_t offset, uint64_t size)
+{
+ RamDiscardListener *rdl;
+
+ QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+ if (!rdl->notify_discard_all) {
+ rdl->notify_discard(rdl, &vmem->memdev->mr, offset, size);
+ }
+ }
+ return 0;
+}
+
+static void virtio_mem_notify_unplug_all(VirtIOMEM *vmem)
+{
+ bool individual_calls = false;
+ RamDiscardListener *rdl;
+
+ if (!vmem->size) {
+ return;
+ }
+
+ QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+ if (rdl->notify_discard_all) {
+ rdl->notify_discard_all(rdl, &vmem->memdev->mr);
+ } else {
+ individual_calls = true;
+ }
+ }
+
+ if (individual_calls) {
+ virtio_mem_for_each_unplugged_range(vmem, NULL,
+ virtio_mem_notify_discard_range_cb);
+ }
+}
+
+static bool virtio_mem_test_bitmap(const VirtIOMEM *vmem, uint64_t start_gpa,
uint64_t size, bool plugged)
{
const unsigned long first_bit = (start_gpa - vmem->addr) / vmem->block_size;
@@ -225,7 +328,8 @@ static void virtio_mem_send_response_simple(VirtIOMEM *vmem,
virtio_mem_send_response(vmem, elem, &resp);
}
-static bool virtio_mem_valid_range(VirtIOMEM *vmem, uint64_t gpa, uint64_t size)
+static bool virtio_mem_valid_range(const VirtIOMEM *vmem, uint64_t gpa,
+ uint64_t size)
{
if (!QEMU_IS_ALIGNED(gpa, vmem->block_size)) {
return false;
@@ -259,6 +363,9 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
strerror(-ret));
return -EBUSY;
}
+ virtio_mem_notify_unplug(vmem, offset, size);
+ } else if (virtio_mem_notify_plug(vmem, offset, size)) {
+ return -EBUSY;
}
virtio_mem_set_bitmap(vmem, start_gpa, size, plug);
return 0;
@@ -356,6 +463,8 @@ static int virtio_mem_unplug_all(VirtIOMEM *vmem)
error_report("Unexpected error discarding RAM: %s", strerror(-ret));
return -EBUSY;
}
+ virtio_mem_notify_unplug_all(vmem);
+
bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
if (vmem->size) {
vmem->size = 0;
@@ -604,6 +713,12 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
vmstate_register_ram(&vmem->memdev->mr, DEVICE(vmem));
qemu_register_reset(virtio_mem_system_reset, vmem);
precopy_add_notifier(&vmem->precopy_notifier);
+
+ /*
+ * Set ourselves as RamDiscardMgr before the plug handler maps the memory
+ * region and exposes it via an address space.
+ */
+ memory_region_set_ram_discard_mgr(&vmem->memdev->mr, RAM_DISCARD_MGR(vmem));
}
static void virtio_mem_device_unrealize(DeviceState *dev)
@@ -611,6 +726,11 @@ static void virtio_mem_device_unrealize(DeviceState *dev)
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtIOMEM *vmem = VIRTIO_MEM(dev);
+ /*
+ * The unplug handler unmapped the memory region, it cannot be
+ * found via an address space anymore. Unset ourselves.
+ */
+ memory_region_set_ram_discard_mgr(&vmem->memdev->mr, NULL);
precopy_remove_notifier(&vmem->precopy_notifier);
qemu_unregister_reset(virtio_mem_system_reset, vmem);
vmstate_unregister_ram(&vmem->memdev->mr, DEVICE(vmem));
@@ -642,13 +762,41 @@ static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
virtio_mem_discard_range_cb);
}
+static int virtio_mem_post_load_replay_cb(const VirtIOMEM *vmem, void *arg,
+ uint64_t offset, uint64_t size)
+{
+ RamDiscardListener *rdl;
+ int ret = 0;
+
+ QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+ ret = rdl->notify_populate(rdl, &vmem->memdev->mr, offset, size);
+ if (ret) {
+ break;
+ }
+ }
+ return ret;
+}
+
static int virtio_mem_post_load(void *opaque, int version_id)
{
+ VirtIOMEM *vmem = VIRTIO_MEM(opaque);
+ int ret;
+
+ /*
+ * We started out with all memory discarded and our memory region is mapped
+ * into an address space. Replay, now that we updated the bitmap.
+ */
+ ret = virtio_mem_for_each_plugged_range(vmem, NULL,
+ virtio_mem_post_load_replay_cb);
+ if (ret) {
+ return ret;
+ }
+
if (migration_in_incoming_postcopy()) {
return 0;
}
- return virtio_mem_restore_unplugged(VIRTIO_MEM(opaque));
+ return virtio_mem_restore_unplugged(vmem);
}
typedef struct VirtIOMEMMigSanityChecks {
@@ -933,6 +1081,7 @@ static void virtio_mem_instance_init(Object *obj)
notifier_list_init(&vmem->size_change_notifiers);
vmem->precopy_notifier.notify = virtio_mem_precopy_notify;
+ QLIST_INIT(&vmem->rdl_list);
object_property_add(obj, VIRTIO_MEM_SIZE_PROP, "size", virtio_mem_get_size,
NULL, NULL, NULL);
@@ -952,11 +1101,77 @@ static Property virtio_mem_properties[] = {
DEFINE_PROP_END_OF_LIST(),
};
+static uint64_t virtio_mem_rdm_get_min_granularity(const RamDiscardMgr *rdm,
+ const MemoryRegion *mr)
+{
+ const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+
+ g_assert(mr == &vmem->memdev->mr);
+ return vmem->block_size;
+}
+
+static bool virtio_mem_rdm_is_populated(const RamDiscardMgr *rdm,
+ const MemoryRegion *mr,
+ ram_addr_t offset, ram_addr_t size)
+{
+ const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+ uint64_t start_gpa = QEMU_ALIGN_DOWN(vmem->addr + offset, vmem->block_size);
+ uint64_t end_gpa = QEMU_ALIGN_UP(vmem->addr + offset + size,
+ vmem->block_size);
+
+ g_assert(mr == &vmem->memdev->mr);
+ if (!virtio_mem_valid_range(vmem, start_gpa, end_gpa - start_gpa)) {
+ return false;
+ }
+
+ return virtio_mem_test_bitmap(vmem, start_gpa, end_gpa - start_gpa, true);
+}
+
+static void virtio_mem_rdm_register_listener(RamDiscardMgr *rdm,
+ const MemoryRegion *mr,
+ RamDiscardListener *rdl)
+{
+ VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+
+ g_assert(mr == &vmem->memdev->mr);
+ QLIST_INSERT_HEAD(&vmem->rdl_list, rdl, next);
+}
+
+static void virtio_mem_rdm_unregister_listener(RamDiscardMgr *rdm,
+ const MemoryRegion *mr,
+ RamDiscardListener *rdl)
+{
+ VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+
+ g_assert(mr == &vmem->memdev->mr);
+ QLIST_REMOVE(rdl, next);
+}
+
+static int virtio_mem_notify_populate_range_cb(const VirtIOMEM *vmem, void *arg,
+ uint64_t offset, uint64_t size)
+{
+ RamDiscardListener *rdl = arg;
+
+ return rdl->notify_populate(rdl, &vmem->memdev->mr, offset, size);
+}
+
+static int virtio_mem_rdm_replay_populated(const RamDiscardMgr *rdm,
+ const MemoryRegion *mr,
+ RamDiscardListener *rdl)
+{
+ const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+
+ g_assert(mr == &vmem->memdev->mr);
+ return virtio_mem_for_each_plugged_range(vmem, rdl,
+ virtio_mem_notify_populate_range_cb);
+}
+
static void virtio_mem_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
VirtIOMEMClass *vmc = VIRTIO_MEM_CLASS(klass);
+ RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_CLASS(klass);
device_class_set_props(dc, virtio_mem_properties);
dc->vmsd = &vmstate_virtio_mem;
@@ -972,6 +1187,12 @@ static void virtio_mem_class_init(ObjectClass *klass, void *data)
vmc->get_memory_region = virtio_mem_get_memory_region;
vmc->add_size_change_notifier = virtio_mem_add_size_change_notifier;
vmc->remove_size_change_notifier = virtio_mem_remove_size_change_notifier;
+
+ rdmc->get_min_granularity = virtio_mem_rdm_get_min_granularity;
+ rdmc->is_populated = virtio_mem_rdm_is_populated;
+ rdmc->register_listener = virtio_mem_rdm_register_listener;
+ rdmc->unregister_listener = virtio_mem_rdm_unregister_listener;
+ rdmc->replay_populated = virtio_mem_rdm_replay_populated;
}
static const TypeInfo virtio_mem_info = {
@@ -981,6 +1202,10 @@ static const TypeInfo virtio_mem_info = {
.instance_init = virtio_mem_instance_init,
.class_init = virtio_mem_class_init,
.class_size = sizeof(VirtIOMEMClass),
+ .interfaces = (InterfaceInfo[]) {
+ { TYPE_RAM_DISCARD_MGR },
+ { }
+ },
};
static void virtio_register_types(void)
diff --git a/include/hw/virtio/virtio-mem.h b/include/hw/virtio/virtio-mem.h
index 4eeb82d5dd..9a6e348fa2 100644
--- a/include/hw/virtio/virtio-mem.h
+++ b/include/hw/virtio/virtio-mem.h
@@ -67,6 +67,9 @@ struct VirtIOMEM {
/* don't migrate unplugged memory */
NotifierWithReturn precopy_notifier;
+
+ /* listeners to notify on plug/unplug activity. */
+ QLIST_HEAD(, RamDiscardListener) rdl_list;
};
struct VirtIOMEMClass {
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (2 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 3/9] virtio-mem: Implement RamDiscardMgr interface David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-12-02 23:26 ` Alex Williamson
2020-11-19 15:39 ` [PATCH v1 5/9] vfio: Support for RamDiscardMgr in the vIOMMU case David Hildenbrand
` (5 subsequent siblings)
9 siblings, 1 reply; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
Implement support for RamDiscardMgr, to prepare for virtio-mem
support. Instead of mapping the whole memory section, we only map
"populated" parts and update the mapping when notified about
discarding/population of memory via the RamDiscardListener. Similarly, when
syncing the dirty bitmaps, sync only the actually mapped (populated) parts
by replaying via the notifier.
Small mapping granularity is problematic for vfio, because we might run out
of mappings. Warn to at least make users aware that there is such a
limitation and that we are dealing with a setup issue e.g., of
virtio-mem devices.
Using virtio-mem with vfio is still blocked via
ram_block_discard_disable()/ram_block_discard_require() after this patch.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/vfio/common.c | 233 ++++++++++++++++++++++++++++++++++
include/hw/vfio/vfio-common.h | 12 ++
2 files changed, 245 insertions(+)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index c1fdbf17f2..d52e7356cb 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -27,6 +27,7 @@
#include "hw/vfio/vfio-common.h"
#include "hw/vfio/vfio.h"
+#include "hw/boards.h"
#include "exec/address-spaces.h"
#include "exec/memory.h"
#include "exec/ram_addr.h"
@@ -39,6 +40,7 @@
#include "trace.h"
#include "qapi/error.h"
#include "migration/migration.h"
+#include "qemu/units.h"
VFIOGroupList vfio_group_list =
QLIST_HEAD_INITIALIZER(vfio_group_list);
@@ -651,6 +653,167 @@ out:
rcu_read_unlock();
}
+static void vfio_ram_discard_notify_discard(RamDiscardListener *rdl,
+ const MemoryRegion *mr,
+ ram_addr_t offset, ram_addr_t size)
+{
+ VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener,
+ listener);
+ const hwaddr mr_start = MAX(offset, vrdl->offset_within_region);
+ const hwaddr mr_end = MIN(offset + size,
+ vrdl->offset_within_region + vrdl->size);
+ const hwaddr iova = mr_start - vrdl->offset_within_region +
+ vrdl->offset_within_address_space;
+ int ret;
+
+ if (mr_start >= mr_end) {
+ return;
+ }
+
+ /* Unmap with a single call. */
+ ret = vfio_dma_unmap(vrdl->container, iova, mr_end - mr_start, NULL);
+ if (ret) {
+ error_report("%s: vfio_dma_unmap() failed: %s", __func__,
+ strerror(-ret));
+ }
+}
+
+static int vfio_ram_discard_notify_populate(RamDiscardListener *rdl,
+ const MemoryRegion *mr,
+ ram_addr_t offset, ram_addr_t size)
+{
+ VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener,
+ listener);
+ const hwaddr mr_end = MIN(offset + size,
+ vrdl->offset_within_region + vrdl->size);
+ hwaddr mr_start = MAX(offset, vrdl->offset_within_region);
+ hwaddr mr_next, iova;
+ void *vaddr;
+ int ret;
+
+ /*
+ * Map in (aligned within memory region) minimum granularity, so we can
+ * unmap in minimum granularity later.
+ */
+ for (; mr_start < mr_end; mr_start = mr_next) {
+ mr_next = QEMU_ALIGN_UP(mr_start + 1, vrdl->granularity);
+ mr_next = MIN(mr_next, mr_end);
+
+ iova = mr_start - vrdl->offset_within_region +
+ vrdl->offset_within_address_space;
+ vaddr = memory_region_get_ram_ptr(vrdl->mr) + mr_start;
+
+ ret = vfio_dma_map(vrdl->container, iova, mr_next - mr_start,
+ vaddr, mr->readonly);
+ if (ret) {
+ /* Rollback */
+ vfio_ram_discard_notify_discard(rdl, mr, offset, size);
+ return ret;
+ }
+ }
+ return 0;
+}
+
+static void vfio_ram_discard_notify_discard_all(RamDiscardListener *rdl,
+ const MemoryRegion *mr)
+{
+ VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener,
+ listener);
+ int ret;
+
+ /* Unmap with a single call. */
+ ret = vfio_dma_unmap(vrdl->container, vrdl->offset_within_address_space,
+ vrdl->size, NULL);
+ if (ret) {
+ error_report("%s: vfio_dma_unmap() failed: %s", __func__,
+ strerror(-ret));
+ }
+}
+
+static void vfio_register_ram_discard_notifier(VFIOContainer *container,
+ MemoryRegionSection *section)
+{
+ RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(section->mr);
+ RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm);
+ MachineState *ms = MACHINE(qdev_get_machine());
+ uint64_t suggested_granularity;
+ VFIORamDiscardListener *vrdl;
+ int ret;
+
+ vrdl = g_new0(VFIORamDiscardListener, 1);
+ vrdl->container = container;
+ vrdl->mr = section->mr;
+ vrdl->offset_within_region = section->offset_within_region;
+ vrdl->offset_within_address_space = section->offset_within_address_space;
+ vrdl->size = int128_get64(section->size);
+ vrdl->granularity = rdmc->get_min_granularity(rdm, section->mr);
+
+ /* Ignore some corner cases not relevant in practice. */
+ g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_region, TARGET_PAGE_SIZE));
+ g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_address_space,
+ TARGET_PAGE_SIZE));
+ g_assert(QEMU_IS_ALIGNED(vrdl->size, TARGET_PAGE_SIZE));
+
+ /*
+ * We assume initial RAM never has a RamDiscardMgr and that all memory
+ * to eventually get hotplugged later could be coordinated via a
+ * RamDiscardMgr ("worst case").
+ *
+ * We assume the Linux kernel is configured ("dma_entry_limit") for the
+ * maximum of 65535 mappings and that we can consume roughly half of that
+ * for this purpose.
+ *
+ * In reality, we might also have RAM without a RamDiscardMgr in our device
+ * memory region and might be able to consume more mappings.
+ */
+ suggested_granularity = pow2ceil((ms->maxram_size - ms->ram_size) / 32768);
+ suggested_granularity = MAX(suggested_granularity, 1 * MiB);
+ if (vrdl->granularity < suggested_granularity) {
+ warn_report("%s: eventually problematic mapping granularity (%" PRId64
+ " MiB) with coordinated discards (e.g., 'block-size' in"
+ " virtio-mem). Suggested minimum granularity: %" PRId64
+ " MiB", __func__, vrdl->granularity / MiB,
+ suggested_granularity / MiB);
+ }
+
+ ram_discard_listener_init(&vrdl->listener,
+ vfio_ram_discard_notify_populate,
+ vfio_ram_discard_notify_discard,
+ vfio_ram_discard_notify_discard_all);
+ rdmc->register_listener(rdm, section->mr, &vrdl->listener);
+ QLIST_INSERT_HEAD(&container->vrdl_list, vrdl, next);
+
+ ret = rdmc->replay_populated(rdm, section->mr, &vrdl->listener);
+ if (ret) {
+ error_report("%s: failed to replay populated memory: %s", __func__,
+ strerror(-ret));
+ }
+}
+
+static void vfio_unregister_ram_discard_listener(VFIOContainer *container,
+ MemoryRegionSection *section)
+{
+ RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(section->mr);
+ RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm);
+ VFIORamDiscardListener *vrdl = NULL;
+
+ QLIST_FOREACH(vrdl, &container->vrdl_list, next) {
+ if (vrdl->mr == section->mr &&
+ vrdl->offset_within_region == section->offset_within_region) {
+ break;
+ }
+ }
+
+ if (!vrdl) {
+ hw_error("vfio: Trying to unregister missing RAM discard listener");
+ }
+
+ rdmc->unregister_listener(rdm, section->mr, &vrdl->listener);
+ QLIST_REMOVE(vrdl, next);
+ g_free(vrdl);
+ /* The caller is expected to vfio_dma_unmap(). */
+}
+
static void vfio_listener_region_add(MemoryListener *listener,
MemoryRegionSection *section)
{
@@ -811,6 +974,16 @@ static void vfio_listener_region_add(MemoryListener *listener,
/* Here we assume that memory_region_is_ram(section->mr)==true */
+ /*
+ * For RAM memory regions with a RamDiscardMgr, we only want to
+ * register the actually "used" parts - and update the mapping whenever
+ * we're notified about changes.
+ */
+ if (memory_region_has_ram_discard_mgr(section->mr)) {
+ vfio_register_ram_discard_notifier(container, section);
+ return;
+ }
+
vaddr = memory_region_get_ram_ptr(section->mr) +
section->offset_within_region +
(iova - section->offset_within_address_space);
@@ -947,6 +1120,10 @@ static void vfio_listener_region_del(MemoryListener *listener,
pgmask = (1ULL << ctz64(hostwin->iova_pgsizes)) - 1;
try_unmap = !((iova & pgmask) || (int128_get64(llsize) & pgmask));
+ } else if (memory_region_has_ram_discard_mgr(section->mr)) {
+ vfio_unregister_ram_discard_listener(container, section);
+ /* We rely on a single vfio_dma_unmap() call below. */
+ try_unmap = true;
}
if (try_unmap) {
@@ -1074,6 +1251,59 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
rcu_read_unlock();
}
+static int vfio_ram_discard_notify_dirty_bitmap(RamDiscardListener *rdl,
+ const MemoryRegion *mr,
+ ram_addr_t offset,
+ ram_addr_t size)
+{
+ VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener,
+ listener);
+ const hwaddr mr_start = MAX(offset, vrdl->offset_within_region);
+ const hwaddr mr_end = MIN(offset + size,
+ vrdl->offset_within_region + vrdl->size);
+ const hwaddr iova = mr_start - vrdl->offset_within_region +
+ vrdl->offset_within_address_space;
+ ram_addr_t ram_addr;
+ int ret;
+
+ if (mr_start >= mr_end) {
+ return 0;
+ }
+
+ /*
+ * Sync the whole mapped region (spanning multiple individual mappings)
+ * in one go.
+ */
+ ram_addr = memory_region_get_ram_addr(vrdl->mr) + mr_start;
+ ret = vfio_get_dirty_bitmap(vrdl->container, iova, mr_end - mr_start,
+ ram_addr);
+ return ret;
+}
+
+static int vfio_sync_ram_discard_listener_dirty_bitmap(VFIOContainer *container,
+ MemoryRegionSection *section)
+{
+ RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(section->mr);
+ RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm);
+ VFIORamDiscardListener tmp_vrdl, *vrdl = NULL;
+
+ QLIST_FOREACH(vrdl, &container->vrdl_list, next) {
+ if (vrdl->mr == section->mr &&
+ vrdl->offset_within_region == section->offset_within_region) {
+ break;
+ }
+ }
+
+ if (!vrdl) {
+ hw_error("vfio: Trying to sync missing RAM discard listener");
+ }
+
+ tmp_vrdl = *vrdl;
+ ram_discard_listener_init(&tmp_vrdl.listener,
+ vfio_ram_discard_notify_dirty_bitmap, NULL, NULL);
+ return rdmc->replay_populated(rdm, section->mr, &tmp_vrdl.listener);
+}
+
static int vfio_sync_dirty_bitmap(VFIOContainer *container,
MemoryRegionSection *section)
{
@@ -1105,6 +1335,8 @@ static int vfio_sync_dirty_bitmap(VFIOContainer *container,
}
}
return 0;
+ } else if (memory_region_has_ram_discard_mgr(section->mr)) {
+ return vfio_sync_ram_discard_listener_dirty_bitmap(container, section);
}
ram_addr = memory_region_get_ram_addr(section->mr) +
@@ -1734,6 +1966,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
container->dirty_pages_supported = false;
QLIST_INIT(&container->giommu_list);
QLIST_INIT(&container->hostwin_list);
+ QLIST_INIT(&container->vrdl_list);
ret = vfio_init_container(container, group->fd, errp);
if (ret) {
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index baeb4dcff1..5895e520aa 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -91,6 +91,7 @@ typedef struct VFIOContainer {
QLIST_HEAD(, VFIOGuestIOMMU) giommu_list;
QLIST_HEAD(, VFIOHostDMAWindow) hostwin_list;
QLIST_HEAD(, VFIOGroup) group_list;
+ QLIST_HEAD(, VFIORamDiscardListener) vrdl_list;
QLIST_ENTRY(VFIOContainer) next;
} VFIOContainer;
@@ -102,6 +103,17 @@ typedef struct VFIOGuestIOMMU {
QLIST_ENTRY(VFIOGuestIOMMU) giommu_next;
} VFIOGuestIOMMU;
+typedef struct VFIORamDiscardListener {
+ VFIOContainer *container;
+ MemoryRegion *mr;
+ hwaddr offset_within_region;
+ hwaddr offset_within_address_space;
+ hwaddr size;
+ uint64_t granularity;
+ RamDiscardListener listener;
+ QLIST_ENTRY(VFIORamDiscardListener) next;
+} VFIORamDiscardListener;
+
typedef struct VFIOHostDMAWindow {
hwaddr min_iova;
hwaddr max_iova;
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 5/9] vfio: Support for RamDiscardMgr in the vIOMMU case
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (3 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 6/9] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
` (4 subsequent siblings)
9 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
vIOMMU support works already with RamDiscardMgr as long as guests only
map populated memory. Both, populated and discarded memory is mapped
into &address_space_memory, where vfio_get_xlat_addr() will find that
memory, to create the vfio mapping.
Sane guests will never map discarded memory (e.g., unplugged memory
blocks in virtio-mem) into an IOMMU - or keep it mapped into an IOMMU while
memory is getting discarded. However, there are two cases where a malicious
guests could trigger pinning of more memory than intended.
One case is easy to handle: the guest trying to map discarded memory
into an IOMMU.
The other case is harder to handle: the guest keeping memory mapped in
the IOMMU while it is getting discarded. We would have to walk over all
mappings when discarding memory and identify if any mapping would be a
violation. Let's keep it simple for now and print a warning, indicating
that setting RLIMIT_MEMLOCK can mitigate such attacks.
We have to take care of incoming migration: at the point the
IOMMUs get restored and start creating mappings in vfio, RamDiscardMgr
implementations might not be back up and running yet. Let's rely on the
runstate. An alternative would be using vmstate priorities - but current
handling is cleaner and more obvious.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/vfio/common.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index d52e7356cb..0d950186f1 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -37,6 +37,7 @@
#include "qemu/range.h"
#include "sysemu/kvm.h"
#include "sysemu/reset.h"
+#include "sysemu/runstate.h"
#include "trace.h"
#include "qapi/error.h"
#include "migration/migration.h"
@@ -573,6 +574,44 @@ static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
error_report("iommu map to non memory area %"HWADDR_PRIx"",
xlat);
return false;
+ } else if (memory_region_has_ram_discard_mgr(mr)) {
+ RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(mr);
+ RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm);
+
+ /*
+ * Malicious VMs can map memory into the IOMMU, which is expected
+ * to remain discarded. vfio will pin all pages, populating memory.
+ * Disallow that.
+ *
+ * Only perform this check when currently running - on incoming
+ * migration, the RamDiscardMgr might not be restored yet, however the
+ * IOMMUs are already getting restored. We trust that the migration
+ * source verified this.
+ */
+ if (runstate_is_running() && !rdmc->is_populated(rdm, mr, xlat, len)) {
+ error_report("iommu map to discarded memory (e.g., unplugged via"
+ " virtio-mem): %"HWADDR_PRIx"",
+ iotlb->translated_addr);
+ return false;
+ }
+
+ /*
+ * Malicious VMs might trigger discarding of IOMMU-mapped memory. The
+ * pages will remain pinned inside vfio until unmapped, resulting in a
+ * higher memory consumption than expected. If memory would get
+ * populated again later, there would be an inconsistency between pages
+ * pinned by vfio and pages seen by QEMU. This is the case until
+ * unmapped from the IOMMU (e.g., during device reset).
+ *
+ * With malicious guests, we really only care about pinning more memory
+ * than expected. RLIMIT_MEMLOCK set for the user/process can never be
+ * exceeded and can be used to mitigate this problem.
+ */
+ warn_report_once("Using vfio with vIOMMUs and coordinated discarding of"
+ " RAM (e.g., virtio-mem) works, however, malicious"
+ " guests can trigger pinning of more memory than"
+ " intended via an IOMMU. It's possible to mitigate "
+ " by setting/adjusting RLIMIT_MEMLOCK.");
}
/*
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 6/9] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require)
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (4 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 5/9] vfio: Support for RamDiscardMgr in the vIOMMU case David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-19 20:34 ` Peter Xu
2020-11-19 15:39 ` [PATCH v1 7/9] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
` (3 subsequent siblings)
9 siblings, 1 reply; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
We have users in migration context that don't hold the BQL (when
finishing migration). To prepare for further changes, use a dedicated mutex
instead of atomic operations. Keep using qatomic_read ("READ_ONCE") for the
functions that only extract the current state (e.g., used by
virtio-balloon), locking isn't necessary.
While at it, split up the counter into two variables to make it easier
to understand.
Suggested-by: Peter Xu <peterx@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
softmmu/physmem.c | 70 ++++++++++++++++++++++++++---------------------
1 file changed, 39 insertions(+), 31 deletions(-)
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 3027747c03..448e4e8c86 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3650,56 +3650,64 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root)
}
}
-/*
- * If positive, discarding RAM is disabled. If negative, discarding RAM is
- * required to work and cannot be disabled.
- */
-static int ram_block_discard_disabled;
+static unsigned int ram_block_discard_requirers;
+static unsigned int ram_block_discard_disablers;
+static QemuMutex ram_block_discard_disable_mutex;
+
+static void ram_block_discard_disable_mutex_lock(void)
+{
+ static gsize initialized;
+
+ if (g_once_init_enter(&initialized)) {
+ qemu_mutex_init(&ram_block_discard_disable_mutex);
+ g_once_init_leave(&initialized, 1);
+ }
+ qemu_mutex_lock(&ram_block_discard_disable_mutex);
+}
+
+static void ram_block_discard_disable_mutex_unlock(void)
+{
+ qemu_mutex_unlock(&ram_block_discard_disable_mutex);
+}
int ram_block_discard_disable(bool state)
{
- int old;
+ int ret = 0;
+ ram_block_discard_disable_mutex_lock();
if (!state) {
- qatomic_dec(&ram_block_discard_disabled);
- return 0;
+ ram_block_discard_disablers--;
+ } else if (!ram_block_discard_requirers) {
+ ram_block_discard_disablers++;
+ } else {
+ ret = -EBUSY;
}
-
- do {
- old = qatomic_read(&ram_block_discard_disabled);
- if (old < 0) {
- return -EBUSY;
- }
- } while (qatomic_cmpxchg(&ram_block_discard_disabled,
- old, old + 1) != old);
- return 0;
+ ram_block_discard_disable_mutex_unlock();
+ return ret;
}
int ram_block_discard_require(bool state)
{
- int old;
+ int ret = 0;
+ ram_block_discard_disable_mutex_lock();
if (!state) {
- qatomic_inc(&ram_block_discard_disabled);
- return 0;
+ ram_block_discard_requirers--;
+ } else if (!ram_block_discard_disablers) {
+ ram_block_discard_requirers++;
+ } else {
+ ret = -EBUSY;
}
-
- do {
- old = qatomic_read(&ram_block_discard_disabled);
- if (old > 0) {
- return -EBUSY;
- }
- } while (qatomic_cmpxchg(&ram_block_discard_disabled,
- old, old - 1) != old);
- return 0;
+ ram_block_discard_disable_mutex_unlock();
+ return ret;
}
bool ram_block_discard_is_disabled(void)
{
- return qatomic_read(&ram_block_discard_disabled) > 0;
+ return qatomic_read(&ram_block_discard_disablers);
}
bool ram_block_discard_is_required(void)
{
- return qatomic_read(&ram_block_discard_disabled) < 0;
+ return qatomic_read(&ram_block_discard_requirers);
}
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 7/9] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (5 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 6/9] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 8/9] virtio-mem: Require only coordinated discards David Hildenbrand
` (2 subsequent siblings)
9 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
We want to separate the two cases whereby we discard ram
- uncoordinated: e.g., virito-balloon
- coordinated: e.g., virtio-mem coordinated via the RamDiscardMgr
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/exec/memory.h | 18 +++++++++++++--
softmmu/physmem.c | 54 ++++++++++++++++++++++++++++++++++++++-----
2 files changed, 64 insertions(+), 8 deletions(-)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 468cbb53a4..a7ec211a60 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2798,6 +2798,12 @@ static inline MemOp devend_memop(enum device_endian end)
*/
int ram_block_discard_disable(bool state);
+/*
+ * See ram_block_discard_disable(): only disable unccordinated discards,
+ * keeping coordinated discards (via the RamDiscardMgr) enabled.
+ */
+int ram_block_uncoordinated_discard_disable(bool state);
+
/*
* Inhibit technologies that disable discarding of pages in RAM blocks.
*
@@ -2807,12 +2813,20 @@ int ram_block_discard_disable(bool state);
int ram_block_discard_require(bool state);
/*
- * Test if discarding of memory in ram blocks is disabled.
+ * See ram_block_discard_require(): only inhibit technologies that disable
+ * uncoordinated discarding of pages in RAM blocks, allowing co-existance with
+ * technologies that only inhibit uncoordinated discards (via the
+ * RamDiscardMgr).
+ */
+int ram_block_coordinated_discard_require(bool state);
+
+/*
+ * Test if any discarding of memory in ram blocks is disabled.
*/
bool ram_block_discard_is_disabled(void);
/*
- * Test if discarding of memory in ram blocks is required to work reliably.
+ * Test if any discarding of memory in ram blocks is required to work reliably.
*/
bool ram_block_discard_is_required(void);
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 448e4e8c86..7a4f3db1b4 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3650,8 +3650,14 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root)
}
}
+/* Require any discards to work. */
static unsigned int ram_block_discard_requirers;
+/* Require only coordinated discards to work. */
+static unsigned int ram_block_coordinated_discard_requirers;
+/* Disable any discards. */
static unsigned int ram_block_discard_disablers;
+/* Disable only uncoordinated disards. */
+static unsigned int ram_block_uncoordinated_discard_disablers;
static QemuMutex ram_block_discard_disable_mutex;
static void ram_block_discard_disable_mutex_lock(void)
@@ -3677,10 +3683,27 @@ int ram_block_discard_disable(bool state)
ram_block_discard_disable_mutex_lock();
if (!state) {
ram_block_discard_disablers--;
- } else if (!ram_block_discard_requirers) {
- ram_block_discard_disablers++;
+ } else if (ram_block_discard_requirers ||
+ ram_block_coordinated_discard_requirers) {
+ ret = -EBUSY;
} else {
+ ram_block_discard_disablers++;
+ }
+ ram_block_discard_disable_mutex_unlock();
+ return ret;
+}
+
+int ram_block_uncoordinated_discard_disable(bool state)
+{
+ int ret = 0;
+
+ ram_block_discard_disable_mutex_lock();
+ if (!state) {
+ ram_block_uncoordinated_discard_disablers--;
+ } else if (ram_block_discard_requirers) {
ret = -EBUSY;
+ } else {
+ ram_block_uncoordinated_discard_disablers++;
}
ram_block_discard_disable_mutex_unlock();
return ret;
@@ -3693,10 +3716,27 @@ int ram_block_discard_require(bool state)
ram_block_discard_disable_mutex_lock();
if (!state) {
ram_block_discard_requirers--;
- } else if (!ram_block_discard_disablers) {
- ram_block_discard_requirers++;
+ } else if (ram_block_discard_disablers ||
+ ram_block_uncoordinated_discard_disablers) {
+ ret = -EBUSY;
} else {
+ ram_block_discard_requirers++;
+ }
+ ram_block_discard_disable_mutex_unlock();
+ return ret;
+}
+
+int ram_block_coordinated_discard_require(bool state)
+{
+ int ret = 0;
+
+ ram_block_discard_disable_mutex_lock();
+ if (!state) {
+ ram_block_coordinated_discard_requirers--;
+ } else if (ram_block_discard_disablers) {
ret = -EBUSY;
+ } else {
+ ram_block_coordinated_discard_requirers++;
}
ram_block_discard_disable_mutex_unlock();
return ret;
@@ -3704,10 +3744,12 @@ int ram_block_discard_require(bool state)
bool ram_block_discard_is_disabled(void)
{
- return qatomic_read(&ram_block_discard_disablers);
+ return qatomic_read(&ram_block_discard_disablers) ||
+ qatomic_read(&ram_block_uncoordinated_discard_disablers);
}
bool ram_block_discard_is_required(void)
{
- return qatomic_read(&ram_block_discard_requirers);
+ return qatomic_read(&ram_block_discard_requirers) ||
+ qatomic_read(&ram_block_coordinated_discard_requirers);
}
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 8/9] virtio-mem: Require only coordinated discards
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (6 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 7/9] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-30 17:20 ` Dr. David Alan Gilbert
2020-11-19 15:39 ` [PATCH v1 9/9] vfio: Disable only uncoordinated discards David Hildenbrand
2020-11-23 11:31 ` [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
9 siblings, 1 reply; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
We implement the RamDiscardMgr interface and only require coordinated
discarding of RAM to work.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/virtio-mem.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 93257b6c26..932d386c37 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -687,7 +687,7 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
return;
}
- if (ram_block_discard_require(true)) {
+ if (ram_block_coordinated_discard_require(true)) {
error_setg(errp, "Discarding RAM is disabled");
return;
}
@@ -695,7 +695,7 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
ret = ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb));
if (ret) {
error_setg_errno(errp, -ret, "Unexpected error discarding RAM");
- ram_block_discard_require(false);
+ ram_block_coordinated_discard_require(false);
return;
}
@@ -738,7 +738,7 @@ static void virtio_mem_device_unrealize(DeviceState *dev)
virtio_del_queue(vdev, 0);
virtio_cleanup(vdev);
g_free(vmem->bitmap);
- ram_block_discard_require(false);
+ ram_block_coordinated_discard_require(false);
}
static int virtio_mem_discard_range_cb(const VirtIOMEM *vmem, void *arg,
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v1 9/9] vfio: Disable only uncoordinated discards
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (7 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 8/9] virtio-mem: Require only coordinated discards David Hildenbrand
@ 2020-11-19 15:39 ` David Hildenbrand
2020-11-23 11:31 ` [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
9 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-19 15:39 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
Dr . David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Igor Mammedov, Paolo Bonzini,
Marek Kedzierski
We support coordinated discarding of RAM using the RamDiscardMgr. Let's
unlock support for coordinated discards, keeping uncoordinated discards
(e.g., via virtio-balloon) disabled.
This unlocks virtio-mem + vfio. Note that vfio used via "nvme://" by the
block layer has to be implemented/unlocked separately. For now,
virtio-mem only supports x86-64 - spapr IOMMUs are not tested/affected.
Note: The block size of a virtio-mem device has to be set to sane sizes,
depending on the maximum hotplug size - to not run out of vfio mappings.
The default virtio-mem block size is usually in the range of a couple of
MBs. The maximum number of mapping is 64k, shared with other users.
Assume you want to hotplug 256GB using virtio-mem - the block size would
have to be set to at least 8 MiB (resulting in 32768 separate mappings).
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/vfio/common.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 0d950186f1..4063a8382f 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1967,8 +1967,10 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
* new memory, it will not yet set ram_block_discard_set_required() and
* therefore, neither stops us here or deals with the sudden memory
* consumption of inflated memory.
+ *
+ * We do support discarding of memory coordinated via the RamDiscardMgr.
*/
- ret = ram_block_discard_disable(true);
+ ret = ram_block_uncoordinated_discard_disable(true);
if (ret) {
error_setg_errno(errp, -ret, "Cannot set discarding of RAM broken");
return ret;
@@ -2144,7 +2146,7 @@ close_fd_exit:
close(fd);
put_space_exit:
- ram_block_discard_disable(false);
+ ram_block_uncoordinated_discard_disable(false);
vfio_put_address_space(space);
return ret;
@@ -2266,7 +2268,7 @@ void vfio_put_group(VFIOGroup *group)
}
if (!group->ram_block_discard_allowed) {
- ram_block_discard_disable(false);
+ ram_block_uncoordinated_discard_disable(false);
}
vfio_kvm_device_del_group(group);
vfio_disconnect_container(group);
@@ -2320,7 +2322,7 @@ int vfio_get_device(VFIOGroup *group, const char *name,
if (!group->ram_block_discard_allowed) {
group->ram_block_discard_allowed = true;
- ram_block_discard_disable(false);
+ ram_block_uncoordinated_discard_disable(false);
}
}
--
2.26.2
^ permalink raw reply related [flat|nested] 17+ messages in thread
* Re: [PATCH v1 6/9] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require)
2020-11-19 15:39 ` [PATCH v1 6/9] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
@ 2020-11-19 20:34 ` Peter Xu
0 siblings, 0 replies; 17+ messages in thread
From: Peter Xu @ 2020-11-19 20:34 UTC (permalink / raw)
To: David Hildenbrand
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, qemu-devel,
Dr . David Alan Gilbert, Auger Eric, Alex Williamson, teawater,
Igor Mammedov, Paolo Bonzini, Luiz Capitulino, Marek Kedzierski
On Thu, Nov 19, 2020 at 04:39:15PM +0100, David Hildenbrand wrote:
> int ram_block_discard_disable(bool state)
> {
> - int old;
> + int ret = 0;
>
> + ram_block_discard_disable_mutex_lock();
> if (!state) {
> - qatomic_dec(&ram_block_discard_disabled);
> - return 0;
> + ram_block_discard_disablers--;
> + } else if (!ram_block_discard_requirers) {
> + ram_block_discard_disablers++;
> + } else {
> + ret = -EBUSY;
> }
I would make things even easier by:
if (ram_block_discard_is_required()) {
return -EBUSY;
}
if (state) {
ram_block_discard_disablers++;
} else {
ram_block_discard_disablers--;
}
But I think it's kind of nitpicking. :)
Reviewed-by: Peter Xu <peterx@redhat.com>
Thanks for writing this patch.
--
Peter Xu
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v1 0/9] virtio-mem: vfio support
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
` (8 preceding siblings ...)
2020-11-19 15:39 ` [PATCH v1 9/9] vfio: Disable only uncoordinated discards David Hildenbrand
@ 2020-11-23 11:31 ` David Hildenbrand
9 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-11-23 11:31 UTC (permalink / raw)
To: qemu-devel
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin,
Dr. David Alan Gilbert, Peter Xu, Luiz Capitulino, Auger Eric,
Alex Williamson, teawater, Paolo Bonzini, Igor Mammedov,
Marek Kedzierski
On 19.11.20 16:39, David Hildenbrand wrote:
> This is the follow-up of:
> https://lkml.kernel.org/r/20200924160423.106747-1-david@redhat.com
> to make vfio and virtio-mem play together. The basic idea was the result of
> Alex brainstorming with me on how to tackle this.
>
> A virtio-mem device manages a memory region in guest physical address
> space, represented as a single (currently large) memory region in QEMU,
> mapped into system memory address space. Before the guest is allowed to use
> memory blocks, it must coordinate with the hypervisor (plug blocks). After
> a reboot, all memory is usually unplugged - when the guest comes up, it
> detects the virtio-mem device and selects memory blocks to plug (based on
> resize requests from the hypervisor).
>
> Memory hot(un)plug consists of (un)plugging memory blocks via a virtio-mem
> device (triggered by the guest). When unplugging blocks, we discard the
> memory - similar to memory balloon inflation. In contrast to memory
> ballooning, we always know which memory blocks a guest may actually use -
> especially during a reboot, after a crash, or after kexec (and during
> hibernation as well). Guests agreed to no access unplugged memory again,
> especially not via DMA.
>
> The issue with vfio is, that it cannot deal with random discards - for this
> reason, virtio-mem and vfio can currently only run mutually exclusive.
> Especially, vfio would currently map the whole memory region (with possible
> only little/no plugged blocks), resulting in all pages getting pinned and
> therefore resulting in a higher memory consumption than expected (turning
> virtio-mem basically useless in these environments).
>
> To make vfio work nicely with virtio-mem, we have to map only the plugged
> blocks, and map/unmap properly when plugging/unplugging blocks (including
> discarding of RAM when unplugging). We achieve that by using a new notifier
> mechanism that communicates changes.
>
> It's important to map memory in the granularity in which we could see
> unmaps again (-> virtio-mem block size) - so when e.g., plugging
> consecutive 100 MB with a block size of 2MB, we need 50 mappings. When
> unmapping, we can use a single vfio_unmap call for the applicable range.
> We expect that the block size of virtio-mem devices will be fairly large
> in the future (to not run out of mappings and to improve hot(un)plug
> performance), configured by the user, when used with vfio (e.g., 128MB,
> 1G, ...).
>
> More info regarding virtio-mem can be found at:
> https://virtio-mem.gitlab.io/
> I'll add a guide for virtio-mem+vfio soonish.
There is now a guide/example at:
https://virtio-mem.gitlab.io/user-guide/user-guide-qemu.html#vfio-vfio-pci
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v1 8/9] virtio-mem: Require only coordinated discards
2020-11-19 15:39 ` [PATCH v1 8/9] virtio-mem: Require only coordinated discards David Hildenbrand
@ 2020-11-30 17:20 ` Dr. David Alan Gilbert
0 siblings, 0 replies; 17+ messages in thread
From: Dr. David Alan Gilbert @ 2020-11-30 17:20 UTC (permalink / raw)
To: David Hildenbrand
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, qemu-devel, Peter Xu,
Luiz Capitulino, Auger Eric, Alex Williamson, teawater,
Igor Mammedov, Paolo Bonzini, Marek Kedzierski
* David Hildenbrand (david@redhat.com) wrote:
> We implement the RamDiscardMgr interface and only require coordinated
> discarding of RAM to work.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Auger Eric <eric.auger@redhat.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: teawater <teawaterz@linux.alibaba.com>
> Cc: Marek Kedzierski <mkedzier@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> hw/virtio/virtio-mem.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
> index 93257b6c26..932d386c37 100644
> --- a/hw/virtio/virtio-mem.c
> +++ b/hw/virtio/virtio-mem.c
> @@ -687,7 +687,7 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
> return;
> }
>
> - if (ram_block_discard_require(true)) {
> + if (ram_block_coordinated_discard_require(true)) {
> error_setg(errp, "Discarding RAM is disabled");
> return;
> }
> @@ -695,7 +695,7 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
> ret = ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb));
> if (ret) {
> error_setg_errno(errp, -ret, "Unexpected error discarding RAM");
> - ram_block_discard_require(false);
> + ram_block_coordinated_discard_require(false);
> return;
> }
>
> @@ -738,7 +738,7 @@ static void virtio_mem_device_unrealize(DeviceState *dev)
> virtio_del_queue(vdev, 0);
> virtio_cleanup(vdev);
> g_free(vmem->bitmap);
> - ram_block_discard_require(false);
> + ram_block_coordinated_discard_require(false);
> }
>
> static int virtio_mem_discard_range_cb(const VirtIOMEM *vmem, void *arg,
> --
> 2.26.2
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions
2020-11-19 15:39 ` [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions David Hildenbrand
@ 2020-12-02 23:26 ` Alex Williamson
2020-12-03 10:04 ` David Hildenbrand
0 siblings, 1 reply; 17+ messages in thread
From: Alex Williamson @ 2020-12-02 23:26 UTC (permalink / raw)
To: David Hildenbrand
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, qemu-devel, Peter Xu,
Dr . David Alan Gilbert, Auger Eric, teawater, Igor Mammedov,
Paolo Bonzini, Luiz Capitulino, Marek Kedzierski
On Thu, 19 Nov 2020 16:39:10 +0100
David Hildenbrand <david@redhat.com> wrote:
> We have some special RAM memory regions (managed by virtio-mem), whereby
> the guest agreed to only use selected memory ranges. "unused" parts are
> discarded so they won't consume memory - to logically unplug these memory
> ranges. Before the VM is allowed to use such logically unplugged memory
> again, coordination with the hypervisor is required.
>
> This results in "sparse" mmaps/RAMBlocks/memory regions, whereby only
> coordinated parts are valid to be used/accessed by the VM.
>
> In most cases, we don't care about that - e.g., in KVM, we simply have a
> single KVM memory slot. However, in case of vfio, registering the
> whole region with the kernel results in all pages getting pinned, and
> therefore an unexpected high memory consumption - discarding of RAM in
> that context is broken.
>
> Let's introduce a way to coordinate discarding/populating memory within a
> RAM memory region with such special consumers of RAM memory regions: they
> can register as listeners and get updates on memory getting discarded and
> populated. Using this machinery, vfio will be able to map only the
> currently populated parts, resulting in discarded parts not getting pinned
> and not consuming memory.
>
> A RamDiscardMgr has to be set for a memory region before it is getting
> mapped, and cannot change while the memory region is mapped.
>
> Note: At some point, we might want to let RAMBlock users (esp. vfio used
> for nvme://) consume this interface as well. We'll need RAMBlock notifier
> calls when a RAMBlock is getting mapped/unmapped (via the corresponding
> memory region), so we can properly register a listener there as well.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Auger Eric <eric.auger@redhat.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: teawater <teawaterz@linux.alibaba.com>
> Cc: Marek Kedzierski <mkedzier@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> include/exec/memory.h | 225 ++++++++++++++++++++++++++++++++++++++++++
> softmmu/memory.c | 22 +++++
> 2 files changed, 247 insertions(+)
>
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 0f3e6bcd5e..468cbb53a4 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
...
> @@ -425,6 +501,120 @@ struct IOMMUMemoryRegionClass {
> Error **errp);
> };
>
> +/*
> + * RamDiscardMgrClass:
> + *
> + * A #RamDiscardMgr coordinates which parts of specific RAM #MemoryRegion
> + * regions are currently populated to be used/accessed by the VM, notifying
> + * after parts were discarded (freeing up memory) and before parts will be
> + * populated (consuming memory), to be used/acessed by the VM.
> + *
> + * A #RamDiscardMgr can only be set for a RAM #MemoryRegion while the
> + * #MemoryRegion isn't mapped yet; it cannot change while the #MemoryRegion is
> + * mapped.
> + *
> + * The #RamDiscardMgr is intended to be used by technologies that are
> + * incompatible with discarding of RAM (e.g., VFIO, which may pin all
> + * memory inside a #MemoryRegion), and require proper coordination to only
> + * map the currently populated parts, to hinder parts that are expected to
> + * remain discarded from silently getting populated and consuming memory.
> + * Technologies that support discarding of RAM don't have to bother and can
> + * simply map the whole #MemoryRegion.
> + *
> + * An example #RamDiscardMgr is virtio-mem, which logically (un)plugs
> + * memory within an assigned RAM #MemoryRegion, coordinated with the VM.
> + * Logically unplugging memory consists of discarding RAM. The VM agreed to not
> + * access unplugged (discarded) memory - especially via DMA. virtio-mem will
> + * properly coordinate with listeners before memory is plugged (populated),
> + * and after memory is unplugged (discarded).
> + *
> + * Listeners are called in multiples of the minimum granularity and changes are
> + * aligned to the minimum granularity within the #MemoryRegion. Listeners have
> + * to prepare for memory becomming discarded in a different granularity than it
> + * was populated and the other way around.
> + */
> +struct RamDiscardMgrClass {
> + /* private */
> + InterfaceClass parent_class;
> +
> + /* public */
> +
> + /**
> + * @get_min_granularity:
> + *
> + * Get the minimum granularity in which listeners will get notified
> + * about changes within the #MemoryRegion via the #RamDiscardMgr.
> + *
> + * @rdm: the #RamDiscardMgr
> + * @mr: the #MemoryRegion
> + *
> + * Returns the minimum granularity.
> + */
> + uint64_t (*get_min_granularity)(const RamDiscardMgr *rdm,
> + const MemoryRegion *mr);
> +
> + /**
> + * @is_populated:
> + *
> + * Check whether the given range within the #MemoryRegion is completely
> + * populated (i.e., no parts are currently discarded). There are no
> + * alignment requirements for the range.
> + *
> + * @rdm: the #RamDiscardMgr
> + * @mr: the #MemoryRegion
> + * @offset: offset into the #MemoryRegion
> + * @size: size in the #MemoryRegion
> + *
> + * Returns the minimum granularity.
I think the return description got copied from above, this returns bool.
...
> diff --git a/softmmu/memory.c b/softmmu/memory.c
> index aa393f1bb0..fbdc50fa8b 100644
> --- a/softmmu/memory.c
> +++ b/softmmu/memory.c
> @@ -2013,6 +2013,21 @@ int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr)
> return imrc->num_indexes(iommu_mr);
> }
>
> +RamDiscardMgr *memory_region_get_ram_discard_mgr(MemoryRegion *mr)
> +{
> + if (!memory_region_is_mapped(mr) || !memory_region_is_ram(mr)) {
> + return false;
s/false/NULL/?
> + }
> + return mr->rdm;
> +}
> +
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case
2020-11-19 15:39 ` [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case David Hildenbrand
@ 2020-12-02 23:26 ` Alex Williamson
2020-12-03 10:07 ` David Hildenbrand
0 siblings, 1 reply; 17+ messages in thread
From: Alex Williamson @ 2020-12-02 23:26 UTC (permalink / raw)
To: David Hildenbrand
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, qemu-devel, Peter Xu,
Dr . David Alan Gilbert, Auger Eric, teawater, Igor Mammedov,
Paolo Bonzini, Luiz Capitulino, Marek Kedzierski
On Thu, 19 Nov 2020 16:39:13 +0100
David Hildenbrand <david@redhat.com> wrote:
> Implement support for RamDiscardMgr, to prepare for virtio-mem
> support. Instead of mapping the whole memory section, we only map
> "populated" parts and update the mapping when notified about
> discarding/population of memory via the RamDiscardListener. Similarly, when
> syncing the dirty bitmaps, sync only the actually mapped (populated) parts
> by replaying via the notifier.
>
> Small mapping granularity is problematic for vfio, because we might run out
> of mappings. Warn to at least make users aware that there is such a
> limitation and that we are dealing with a setup issue e.g., of
> virtio-mem devices.
>
> Using virtio-mem with vfio is still blocked via
> ram_block_discard_disable()/ram_block_discard_require() after this patch.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Auger Eric <eric.auger@redhat.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: teawater <teawaterz@linux.alibaba.com>
> Cc: Marek Kedzierski <mkedzier@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> hw/vfio/common.c | 233 ++++++++++++++++++++++++++++++++++
> include/hw/vfio/vfio-common.h | 12 ++
> 2 files changed, 245 insertions(+)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index c1fdbf17f2..d52e7356cb 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
...
> +static void vfio_register_ram_discard_notifier(VFIOContainer *container,
> + MemoryRegionSection *section)
> +{
> + RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(section->mr);
> + RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm);
> + MachineState *ms = MACHINE(qdev_get_machine());
> + uint64_t suggested_granularity;
> + VFIORamDiscardListener *vrdl;
> + int ret;
> +
> + vrdl = g_new0(VFIORamDiscardListener, 1);
> + vrdl->container = container;
> + vrdl->mr = section->mr;
> + vrdl->offset_within_region = section->offset_within_region;
> + vrdl->offset_within_address_space = section->offset_within_address_space;
> + vrdl->size = int128_get64(section->size);
> + vrdl->granularity = rdmc->get_min_granularity(rdm, section->mr);
> +
> + /* Ignore some corner cases not relevant in practice. */
> + g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_region, TARGET_PAGE_SIZE));
> + g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_address_space,
> + TARGET_PAGE_SIZE));
> + g_assert(QEMU_IS_ALIGNED(vrdl->size, TARGET_PAGE_SIZE));
> +
> + /*
> + * We assume initial RAM never has a RamDiscardMgr and that all memory
> + * to eventually get hotplugged later could be coordinated via a
> + * RamDiscardMgr ("worst case").
> + *
> + * We assume the Linux kernel is configured ("dma_entry_limit") for the
> + * maximum of 65535 mappings and that we can consume roughly half of that
s/maximum/default/
Deciding we should only use half of it seems arbitrary.
> + * for this purpose.
> + *
> + * In reality, we might also have RAM without a RamDiscardMgr in our device
> + * memory region and might be able to consume more mappings.
> + */
> + suggested_granularity = pow2ceil((ms->maxram_size - ms->ram_size) / 32768);
> + suggested_granularity = MAX(suggested_granularity, 1 * MiB);
> + if (vrdl->granularity < suggested_granularity) {
> + warn_report("%s: eventually problematic mapping granularity (%" PRId64
> + " MiB) with coordinated discards (e.g., 'block-size' in"
> + " virtio-mem). Suggested minimum granularity: %" PRId64
> + " MiB", __func__, vrdl->granularity / MiB,
> + suggested_granularity / MiB);
> + }
Starting w/ kernel 5.10 we have a way to get the instantaneous count of
available DMA mappings, so we could avoid assuming 64k when that's
available (see ex. s390_pci_update_dma_avail()). Thanks,
Alex
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions
2020-12-02 23:26 ` Alex Williamson
@ 2020-12-03 10:04 ` David Hildenbrand
0 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-12-03 10:04 UTC (permalink / raw)
To: Alex Williamson
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, qemu-devel, Peter Xu,
Dr . David Alan Gilbert, Auger Eric, teawater, Igor Mammedov,
Paolo Bonzini, Luiz Capitulino, Marek Kedzierski
On 03.12.20 00:26, Alex Williamson wrote:
> On Thu, 19 Nov 2020 16:39:10 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
>> We have some special RAM memory regions (managed by virtio-mem), whereby
>> the guest agreed to only use selected memory ranges. "unused" parts are
>> discarded so they won't consume memory - to logically unplug these memory
>> ranges. Before the VM is allowed to use such logically unplugged memory
>> again, coordination with the hypervisor is required.
>>
>> This results in "sparse" mmaps/RAMBlocks/memory regions, whereby only
>> coordinated parts are valid to be used/accessed by the VM.
>>
>> In most cases, we don't care about that - e.g., in KVM, we simply have a
>> single KVM memory slot. However, in case of vfio, registering the
>> whole region with the kernel results in all pages getting pinned, and
>> therefore an unexpected high memory consumption - discarding of RAM in
>> that context is broken.
>>
>> Let's introduce a way to coordinate discarding/populating memory within a
>> RAM memory region with such special consumers of RAM memory regions: they
>> can register as listeners and get updates on memory getting discarded and
>> populated. Using this machinery, vfio will be able to map only the
>> currently populated parts, resulting in discarded parts not getting pinned
>> and not consuming memory.
>>
>> A RamDiscardMgr has to be set for a memory region before it is getting
>> mapped, and cannot change while the memory region is mapped.
>>
>> Note: At some point, we might want to let RAMBlock users (esp. vfio used
>> for nvme://) consume this interface as well. We'll need RAMBlock notifier
>> calls when a RAMBlock is getting mapped/unmapped (via the corresponding
>> memory region), so we can properly register a listener there as well.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>> Cc: Alex Williamson <alex.williamson@redhat.com>
>> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> Cc: Igor Mammedov <imammedo@redhat.com>
>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>> Cc: Peter Xu <peterx@redhat.com>
>> Cc: Auger Eric <eric.auger@redhat.com>
>> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
>> Cc: teawater <teawaterz@linux.alibaba.com>
>> Cc: Marek Kedzierski <mkedzier@redhat.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>> include/exec/memory.h | 225 ++++++++++++++++++++++++++++++++++++++++++
>> softmmu/memory.c | 22 +++++
>> 2 files changed, 247 insertions(+)
>>
>> diff --git a/include/exec/memory.h b/include/exec/memory.h
>> index 0f3e6bcd5e..468cbb53a4 100644
>> --- a/include/exec/memory.h
>> +++ b/include/exec/memory.h
> ...
>> @@ -425,6 +501,120 @@ struct IOMMUMemoryRegionClass {
>> Error **errp);
>> };
>>
>> +/*
>> + * RamDiscardMgrClass:
>> + *
>> + * A #RamDiscardMgr coordinates which parts of specific RAM #MemoryRegion
>> + * regions are currently populated to be used/accessed by the VM, notifying
>> + * after parts were discarded (freeing up memory) and before parts will be
>> + * populated (consuming memory), to be used/acessed by the VM.
>> + *
>> + * A #RamDiscardMgr can only be set for a RAM #MemoryRegion while the
>> + * #MemoryRegion isn't mapped yet; it cannot change while the #MemoryRegion is
>> + * mapped.
>> + *
>> + * The #RamDiscardMgr is intended to be used by technologies that are
>> + * incompatible with discarding of RAM (e.g., VFIO, which may pin all
>> + * memory inside a #MemoryRegion), and require proper coordination to only
>> + * map the currently populated parts, to hinder parts that are expected to
>> + * remain discarded from silently getting populated and consuming memory.
>> + * Technologies that support discarding of RAM don't have to bother and can
>> + * simply map the whole #MemoryRegion.
>> + *
>> + * An example #RamDiscardMgr is virtio-mem, which logically (un)plugs
>> + * memory within an assigned RAM #MemoryRegion, coordinated with the VM.
>> + * Logically unplugging memory consists of discarding RAM. The VM agreed to not
>> + * access unplugged (discarded) memory - especially via DMA. virtio-mem will
>> + * properly coordinate with listeners before memory is plugged (populated),
>> + * and after memory is unplugged (discarded).
>> + *
>> + * Listeners are called in multiples of the minimum granularity and changes are
>> + * aligned to the minimum granularity within the #MemoryRegion. Listeners have
>> + * to prepare for memory becomming discarded in a different granularity than it
>> + * was populated and the other way around.
>> + */
>> +struct RamDiscardMgrClass {
>> + /* private */
>> + InterfaceClass parent_class;
>> +
>> + /* public */
>> +
>> + /**
>> + * @get_min_granularity:
>> + *
>> + * Get the minimum granularity in which listeners will get notified
>> + * about changes within the #MemoryRegion via the #RamDiscardMgr.
>> + *
>> + * @rdm: the #RamDiscardMgr
>> + * @mr: the #MemoryRegion
>> + *
>> + * Returns the minimum granularity.
>> + */
>> + uint64_t (*get_min_granularity)(const RamDiscardMgr *rdm,
>> + const MemoryRegion *mr);
>> +
>> + /**
>> + * @is_populated:
>> + *
>> + * Check whether the given range within the #MemoryRegion is completely
>> + * populated (i.e., no parts are currently discarded). There are no
>> + * alignment requirements for the range.
>> + *
>> + * @rdm: the #RamDiscardMgr
>> + * @mr: the #MemoryRegion
>> + * @offset: offset into the #MemoryRegion
>> + * @size: size in the #MemoryRegion
>> + *
>> + * Returns the minimum granularity.
>
>
> I think the return description got copied from above, this returns bool.
Ah, thanks for catching that.
>
> ...
>> diff --git a/softmmu/memory.c b/softmmu/memory.c
>> index aa393f1bb0..fbdc50fa8b 100644
>> --- a/softmmu/memory.c
>> +++ b/softmmu/memory.c
>> @@ -2013,6 +2013,21 @@ int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr)
>> return imrc->num_indexes(iommu_mr);
>> }
>>
>> +RamDiscardMgr *memory_region_get_ram_discard_mgr(MemoryRegion *mr)
>> +{
>> + if (!memory_region_is_mapped(mr) || !memory_region_is_ram(mr)) {
>> + return false;
>
> s/false/NULL/?
Thanks!
I think I've been reworking this patch too often :)
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case
2020-12-02 23:26 ` Alex Williamson
@ 2020-12-03 10:07 ` David Hildenbrand
0 siblings, 0 replies; 17+ messages in thread
From: David Hildenbrand @ 2020-12-03 10:07 UTC (permalink / raw)
To: Alex Williamson
Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, qemu-devel, Peter Xu,
Dr . David Alan Gilbert, Auger Eric, teawater, Igor Mammedov,
Paolo Bonzini, Luiz Capitulino, Marek Kedzierski
On 03.12.20 00:26, Alex Williamson wrote:
> On Thu, 19 Nov 2020 16:39:13 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
>> Implement support for RamDiscardMgr, to prepare for virtio-mem
>> support. Instead of mapping the whole memory section, we only map
>> "populated" parts and update the mapping when notified about
>> discarding/population of memory via the RamDiscardListener. Similarly, when
>> syncing the dirty bitmaps, sync only the actually mapped (populated) parts
>> by replaying via the notifier.
>>
>> Small mapping granularity is problematic for vfio, because we might run out
>> of mappings. Warn to at least make users aware that there is such a
>> limitation and that we are dealing with a setup issue e.g., of
>> virtio-mem devices.
>>
>> Using virtio-mem with vfio is still blocked via
>> ram_block_discard_disable()/ram_block_discard_require() after this patch.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>> Cc: Alex Williamson <alex.williamson@redhat.com>
>> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> Cc: Igor Mammedov <imammedo@redhat.com>
>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>> Cc: Peter Xu <peterx@redhat.com>
>> Cc: Auger Eric <eric.auger@redhat.com>
>> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
>> Cc: teawater <teawaterz@linux.alibaba.com>
>> Cc: Marek Kedzierski <mkedzier@redhat.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>> hw/vfio/common.c | 233 ++++++++++++++++++++++++++++++++++
>> include/hw/vfio/vfio-common.h | 12 ++
>> 2 files changed, 245 insertions(+)
>>
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index c1fdbf17f2..d52e7356cb 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
> ...
>> +static void vfio_register_ram_discard_notifier(VFIOContainer *container,
>> + MemoryRegionSection *section)
>> +{
>> + RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(section->mr);
>> + RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm);
>> + MachineState *ms = MACHINE(qdev_get_machine());
>> + uint64_t suggested_granularity;
>> + VFIORamDiscardListener *vrdl;
>> + int ret;
>> +
>> + vrdl = g_new0(VFIORamDiscardListener, 1);
>> + vrdl->container = container;
>> + vrdl->mr = section->mr;
>> + vrdl->offset_within_region = section->offset_within_region;
>> + vrdl->offset_within_address_space = section->offset_within_address_space;
>> + vrdl->size = int128_get64(section->size);
>> + vrdl->granularity = rdmc->get_min_granularity(rdm, section->mr);
>> +
>> + /* Ignore some corner cases not relevant in practice. */
>> + g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_region, TARGET_PAGE_SIZE));
>> + g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_address_space,
>> + TARGET_PAGE_SIZE));
>> + g_assert(QEMU_IS_ALIGNED(vrdl->size, TARGET_PAGE_SIZE));
>> +
>> + /*
>> + * We assume initial RAM never has a RamDiscardMgr and that all memory
>> + * to eventually get hotplugged later could be coordinated via a
>> + * RamDiscardMgr ("worst case").
>> + *
>> + * We assume the Linux kernel is configured ("dma_entry_limit") for the
>> + * maximum of 65535 mappings and that we can consume roughly half of that
>
>
> s/maximum/default/
>
> Deciding we should only use half of it seems arbitrary.
Yeah, it's sub-optimal - bad heuristic :) . What would be your
suggestion for a better heuristic? My gut feeling would be that we
rarely use more than 512 mappings in the system address space (e.g.,
maximum number of DIMMs is 256).
>
>
>> + * for this purpose.
>> + *
>> + * In reality, we might also have RAM without a RamDiscardMgr in our device
>> + * memory region and might be able to consume more mappings.
>> + */
>> + suggested_granularity = pow2ceil((ms->maxram_size - ms->ram_size) / 32768);
>> + suggested_granularity = MAX(suggested_granularity, 1 * MiB);
>> + if (vrdl->granularity < suggested_granularity) {
>> + warn_report("%s: eventually problematic mapping granularity (%" PRId64
>> + " MiB) with coordinated discards (e.g., 'block-size' in"
>> + " virtio-mem). Suggested minimum granularity: %" PRId64
>> + " MiB", __func__, vrdl->granularity / MiB,
>> + suggested_granularity / MiB);
>> + }
>
>
> Starting w/ kernel 5.10 we have a way to get the instantaneous count of
> available DMA mappings, so we could avoid assuming 64k when that's
> available (see ex. s390_pci_update_dma_avail()).
Interesting, I missed that interface. Will have a look. TThanks!
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 17+ messages in thread
end of thread, other threads:[~2020-12-03 10:08 UTC | newest]
Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-19 15:39 [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 1/9] memory: Introduce RamDiscardMgr for RAM memory regions David Hildenbrand
2020-12-02 23:26 ` Alex Williamson
2020-12-03 10:04 ` David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 2/9] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 3/9] virtio-mem: Implement RamDiscardMgr interface David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 4/9] vfio: Support for RamDiscardMgr in the !vIOMMU case David Hildenbrand
2020-12-02 23:26 ` Alex Williamson
2020-12-03 10:07 ` David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 5/9] vfio: Support for RamDiscardMgr in the vIOMMU case David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 6/9] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
2020-11-19 20:34 ` Peter Xu
2020-11-19 15:39 ` [PATCH v1 7/9] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
2020-11-19 15:39 ` [PATCH v1 8/9] virtio-mem: Require only coordinated discards David Hildenbrand
2020-11-30 17:20 ` Dr. David Alan Gilbert
2020-11-19 15:39 ` [PATCH v1 9/9] vfio: Disable only uncoordinated discards David Hildenbrand
2020-11-23 11:31 ` [PATCH v1 0/9] virtio-mem: vfio support David Hildenbrand
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