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* [PATCH RESEND v7 00/13] virtio-mem: vfio support
@ 2021-04-13  9:55 David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 01/13] memory: Introduce RamDiscardManager for RAM memory regions David Hildenbrand
                   ` (12 more replies)
  0 siblings, 13 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, David Hildenbrand, Michael S. Tsirkin,
	Dr. David Alan Gilbert, Peter Xu, Pankaj Gupta, Auger Eric,
	Alex Williamson, teawater, Paolo Bonzini, Igor Mammedov,
	Marek Kedzierski

After silence for more than 1.5 months and the feeling like pinging into a
black hole, I rebased and retested the patches.

I hope we can get them into 6.1 early -- or at least get some more feedback
on the patches.

@Paolo: Michael and Alex already acked relevant parts

--

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 not 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 2 MB, 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, ...), but it will depend on the setup.

More info regarding virtio-mem can be found at:
    https://virtio-mem.gitlab.io/

v7 is located at:
  git@github.com:davidhildenbrand/qemu.git virtio-mem-vfio-v7

v6 -> v7:
- s/RamDiscardMgr/RamDiscardManager/
- "memory: Introduce RamDiscardManager for RAM memory regions"
-- Make RamDiscardManager/RamDiscardListener eat MemoryRegionSections
-- Replace notify_discard_all callback by double_discard_supported
-- Reshuffle the individual hunks in memory.h
-- Provide function wrappers for RamDiscardManager calls
- "memory: Helpers to copy/free a MemoryRegionSection"
-- Added
- "virtio-mem: Implement RamDiscardManager interface"
-- Work on MemoryRegionSections instead of ranges
-- Minor optimizations
- "vfio: Support for RamDiscardManager in the !vIOMMU case"
-- Simplify based on new interfaces /  MemoryRegionSections
-- Minor cleanups and optimizations
-- Add a comment regarding dirty bitmap sync.
-- Don't store "offset_within_region" in VFIORamDiscardListener
- "vfio: Support for RamDiscardManager in the vIOMMU case"
-- Adjust to new interface
- "softmmu/physmem: Don't use atomic operations in ..."
-- Rename variables
- "softmmu/physmem: Extend ram_block_discard_(require|disable) ..."
-- Rename variables
- Rebased and retested

v5 -> v6:
- "memory: Introduce RamDiscardMgr for RAM memory regions"
-- Fix variable names in one prototype.
- "virtio-mem: Don't report errors when ram_block_discard_range() fails"
-- Added
- "virtio-mem: Implement RamDiscardMgr interface"
-- Don't report an error if discarding fails
- Rebased and retested

v4 -> v5:
- "vfio: Support for RamDiscardMgr in the !vIOMMU case"
-- Added more assertions for granularity vs. iommu supported pagesize
- "vfio: Sanity check maximum number of DMA mappings with RamDiscardMgr"
-- Fix accounting of mappings
- "vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus"
-- Fence off SPAPR and add some comments regarding future support.
-- Tweak patch description
- Rebase and retest

v3 -> v4:
- "vfio: Query and store the maximum number of DMA mappings
-- Limit the patch to querying and storing only
-- Renamed to "vfio: Query and store the maximum number of possible DMA
   mappings"
- "vfio: Support for RamDiscardMgr in the !vIOMMU case"
-- Remove sanity checks / warning the user
- "vfio: Sanity check maximum number of DMA mappings with RamDiscardMgr"
-- Perform sanity checks by looking at the number of memslots and all
   registered RamDiscardMgr sections
- Rebase and retest
- Reshuffled the patches slightly

v2 -> v3:
- Rebased + retested
- Fixed some typos
- Added RB's

v1 -> v2:
- "memory: Introduce RamDiscardMgr for RAM memory regions"
-- Fix some errors in the documentation
-- Make register_listener() notify about populated parts and
   unregister_listener() notify about discarding populated parts, to
   simplify future locking inside virtio-mem, when handling requests via a
   separate thread.
- "vfio: Query and store the maximum number of DMA mappings"
-- Query number of mappings and track mappings (except for vIOMMU)
- "vfio: Support for RamDiscardMgr in the !vIOMMU case"
-- Adapt to RamDiscardMgr changes and warn via generic DMA reservation
- "vfio: Support for RamDiscardMgr in the vIOMMU case"
-- Use vmstate priority to handle migration dependencies

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 (13):
  memory: Introduce RamDiscardManager for RAM memory regions
  memory: Helpers to copy/free a MemoryRegionSection
  virtio-mem: Factor out traversing unplugged ranges
  virtio-mem: Don't report errors when ram_block_discard_range() fails
  virtio-mem: Implement RamDiscardManager interface
  vfio: Support for RamDiscardManager in the !vIOMMU case
  vfio: Query and store the maximum number of possible DMA mappings
  vfio: Sanity check maximum number of DMA mappings with
    RamDiscardManager
  vfio: Support for RamDiscardManager 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 for VFIO_TYPE1 iommus

 hw/vfio/common.c               | 315 +++++++++++++++++++++++++-
 hw/virtio/virtio-mem.c         | 391 ++++++++++++++++++++++++++++-----
 include/exec/memory.h          | 324 +++++++++++++++++++++++++--
 include/hw/vfio/vfio-common.h  |  12 +
 include/hw/virtio/virtio-mem.h |   3 +
 include/migration/vmstate.h    |   1 +
 softmmu/memory.c               |  98 +++++++++
 softmmu/physmem.c              | 108 ++++++---
 8 files changed, 1133 insertions(+), 119 deletions(-)

-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 01/13] memory: Introduce RamDiscardManager for RAM memory regions
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 02/13] memory: Helpers to copy/free a MemoryRegionSection David Hildenbrand
                   ` (11 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Alex Williamson, Peter Xu, Dr . David Alan Gilbert, Auger Eric,
	Pankaj Gupta, 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 RamDiscardManager 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.

Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 include/exec/memory.h | 286 ++++++++++++++++++++++++++++++++++++++----
 softmmu/memory.c      |  71 +++++++++++
 2 files changed, 335 insertions(+), 22 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 5728a681b2..38a3b41ac1 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_MANAGER "qemu:ram-discard-manager"
+typedef struct RamDiscardManagerClass RamDiscardManagerClass;
+typedef struct RamDiscardManager RamDiscardManager;
+DECLARE_OBJ_CHECKERS(RamDiscardManager, RamDiscardManagerClass,
+                     RAM_DISCARD_MANAGER, TYPE_RAM_DISCARD_MANAGER);
+
 #ifdef CONFIG_FUZZ
 void fuzz_dma_read_cb(size_t addr,
                       size_t len,
@@ -65,6 +71,28 @@ struct ReservedRegion {
     unsigned type;
 };
 
+/**
+ * struct MemoryRegionSection: describes a fragment of a #MemoryRegion
+ *
+ * @mr: the region, or %NULL if empty
+ * @fv: the flat view of the address space the region is mapped in
+ * @offset_within_region: the beginning of the section, relative to @mr's start
+ * @size: the size of the section; will not exceed @mr's boundaries
+ * @offset_within_address_space: the address of the first byte of the section
+ *     relative to the region's address space
+ * @readonly: writes to this section are ignored
+ * @nonvolatile: this section is non-volatile
+ */
+struct MemoryRegionSection {
+    Int128 size;
+    MemoryRegion *mr;
+    FlatView *fv;
+    hwaddr offset_within_region;
+    hwaddr offset_within_address_space;
+    bool readonly;
+    bool nonvolatile;
+};
+
 typedef struct IOMMUTLBEntry IOMMUTLBEntry;
 
 /* See address_space_translate: bit 0 is read, bit 1 is write.  */
@@ -441,6 +469,206 @@ struct IOMMUMemoryRegionClass {
                                      Error **errp);
 };
 
+typedef struct RamDiscardListener RamDiscardListener;
+typedef int (*NotifyRamPopulate)(RamDiscardListener *rdl,
+                                 MemoryRegionSection *section);
+typedef void (*NotifyRamDiscard)(RamDiscardListener *rdl,
+                                 MemoryRegionSection *section);
+
+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
+     * @section: the #MemoryRegionSection to get populated. The section
+     *           is aligned within the memory region to the minimum granularity
+     *           unless it would exceed the registered section.
+     *
+     * 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
+     * @section: the #MemoryRegionSection to get populated. The section
+     *           is aligned within the memory region to the minimum granularity
+     *           unless it would exceed the registered section.
+     */
+    NotifyRamDiscard notify_discard;
+
+    /*
+     * @double_discard_supported:
+     *
+     * The listener suppors getting @notify_discard notifications that span
+     * already discarded parts.
+     */
+    bool double_discard_supported;
+
+    MemoryRegionSection *section;
+    QLIST_ENTRY(RamDiscardListener) next;
+};
+
+static inline void ram_discard_listener_init(RamDiscardListener *rdl,
+                                             NotifyRamPopulate populate_fn,
+                                             NotifyRamDiscard discard_fn,
+                                             bool double_discard_supported)
+{
+    rdl->notify_populate = populate_fn;
+    rdl->notify_discard = discard_fn;
+    rdl->double_discard_supported = double_discard_supported;
+}
+
+typedef int (*ReplayRamPopulate)(MemoryRegionSection *section, void *opaque);
+
+/*
+ * RamDiscardManagerClass:
+ *
+ * A #RamDiscardManager 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 #RamDiscardManager can only be set for a RAM #MemoryRegion while the
+ * #MemoryRegion isn't mapped yet; it cannot change while the #MemoryRegion is
+ * mapped.
+ *
+ * The #RamDiscardManager 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 #RamDiscardManager 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 (unless it
+ * would exceed the registered range) 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 RamDiscardManagerClass {
+    /* 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 #RamDiscardManager.
+     *
+     * @rdm: the #RamDiscardManager
+     * @mr: the #MemoryRegion
+     *
+     * Returns the minimum granularity.
+     */
+    uint64_t (*get_min_granularity)(const RamDiscardManager *rdm,
+                                    const MemoryRegion *mr);
+
+    /**
+     * @is_populated:
+     *
+     * Check whether the given #MemoryRegionSection is completely populated
+     * (i.e., no parts are currently discarded) via the #RamDiscardManager.
+     * There are no alignment requirements.
+     *
+     * @rdm: the #RamDiscardManager
+     * @section: the #MemoryRegionSection
+     *
+     * Returns whether the given range is completely populated.
+     */
+    bool (*is_populated)(const RamDiscardManager *rdm,
+                         const MemoryRegionSection *section);
+
+    /**
+     * @replay_populated:
+     *
+     * Call the #ReplayRamPopulate callback for all populated parts within the
+     * #MemoryRegionSection via the #RamDiscardManager.
+     *
+     * In case any call fails, no further calls are made.
+     *
+     * @rdm: the #RamDiscardManager
+     * @section: the #MemoryRegionSection
+     * @replay_fn: the #ReplayRamPopulate callback
+     * @opaque: pointer to forward to the callback
+     *
+     * Returns 0 on success, or a negative error if any notification failed.
+     */
+    int (*replay_populated)(const RamDiscardManager *rdm,
+                            MemoryRegionSection *section,
+                            ReplayRamPopulate replay_fn, void *opaque);
+
+    /**
+     * @register_listener:
+     *
+     * Register a #RamDiscardListener for the given #MemoryRegionSection and
+     * immediately notify the #RamDiscardListener about all populated parts
+     * within the #MemoryRegionSection via the #RamDiscardManager.
+     *
+     * In case any notification fails, no further notifications are triggered
+     * and an error is logged.
+     *
+     * @rdm: the #RamDiscardManager
+     * @rdl: the #RamDiscardListener
+     * @section: the #MemoryRegionSection
+     */
+    void (*register_listener)(RamDiscardManager *rdm,
+                              RamDiscardListener *rdl,
+                              MemoryRegionSection *section);
+
+    /**
+     * @unregister_listener:
+     *
+     * Unregister a previously registered #RamDiscardListener via the
+     * #RamDiscardManager after notifying the #RamDiscardListener about all
+     * populated parts becoming unpopulated within the registered
+     * #MemoryRegionSection.
+     *
+     * @rdm: the #RamDiscardManager
+     * @rdl: the #RamDiscardListener
+     */
+    void (*unregister_listener)(RamDiscardManager *rdm,
+                                RamDiscardListener *rdl);
+};
+
+uint64_t ram_discard_manager_get_min_granularity(const RamDiscardManager *rdm,
+                                                 const MemoryRegion *mr);
+
+bool ram_discard_manager_is_populated(const RamDiscardManager *rdm,
+                                      const MemoryRegionSection *section);
+
+int ram_discard_manager_replay_populated(const RamDiscardManager *rdm,
+                                         MemoryRegionSection *section,
+                                         ReplayRamPopulate replay_fn,
+                                         void *opaque);
+
+void ram_discard_manager_register_listener(RamDiscardManager *rdm,
+                                           RamDiscardListener *rdl,
+                                           MemoryRegionSection *section);
+
+void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
+                                             RamDiscardListener *rdl);
+
 typedef struct CoalescedMemoryRange CoalescedMemoryRange;
 typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
 
@@ -487,6 +715,7 @@ struct MemoryRegion {
     const char *name;
     unsigned ioeventfd_nb;
     MemoryRegionIoeventfd *ioeventfds;
+    RamDiscardManager *rdm; /* Only for RAM */
 };
 
 struct IOMMUMemoryRegion {
@@ -806,28 +1035,6 @@ typedef bool (*flatview_cb)(Int128 start,
  */
 void flatview_for_each_range(FlatView *fv, flatview_cb cb, void *opaque);
 
-/**
- * struct MemoryRegionSection: describes a fragment of a #MemoryRegion
- *
- * @mr: the region, or %NULL if empty
- * @fv: the flat view of the address space the region is mapped in
- * @offset_within_region: the beginning of the section, relative to @mr's start
- * @size: the size of the section; will not exceed @mr's boundaries
- * @offset_within_address_space: the address of the first byte of the section
- *     relative to the region's address space
- * @readonly: writes to this section are ignored
- * @nonvolatile: this section is non-volatile
- */
-struct MemoryRegionSection {
-    Int128 size;
-    MemoryRegion *mr;
-    FlatView *fv;
-    hwaddr offset_within_region;
-    hwaddr offset_within_address_space;
-    bool readonly;
-    bool nonvolatile;
-};
-
 static inline bool MemoryRegionSection_eq(MemoryRegionSection *a,
                                           MemoryRegionSection *b)
 {
@@ -2003,6 +2210,41 @@ bool memory_region_present(MemoryRegion *container, hwaddr addr);
  */
 bool memory_region_is_mapped(MemoryRegion *mr);
 
+/**
+ * memory_region_get_ram_discard_manager: get the #RamDiscardManager for a
+ * #MemoryRegion
+ *
+ * The #RamDiscardManager cannot change while a memory region is mapped.
+ *
+ * @mr: the #MemoryRegion
+ */
+RamDiscardManager *memory_region_get_ram_discard_manager(MemoryRegion *mr);
+
+/**
+ * memory_region_has_ram_discard_manager: check whether a #MemoryRegion has a
+ * #RamDiscardManager assigned
+ *
+ * @mr: the #MemoryRegion
+ */
+static inline bool memory_region_has_ram_discard_manager(MemoryRegion *mr)
+{
+    return !!memory_region_get_ram_discard_manager(mr);
+}
+
+/**
+ * memory_region_set_ram_discard_manager: set the #RamDiscardManager 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
+ * #RamDiscardManager assigned.
+ *
+ * @mr: the #MemoryRegion
+ * @urn: #RamDiscardManager to set
+ */
+void memory_region_set_ram_discard_manager(MemoryRegion *mr,
+                                           RamDiscardManager *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 d4493ef9e4..26ea87d77a 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2030,6 +2030,70 @@ int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr)
     return imrc->num_indexes(iommu_mr);
 }
 
+RamDiscardManager *memory_region_get_ram_discard_manager(MemoryRegion *mr)
+{
+    if (!memory_region_is_mapped(mr) || !memory_region_is_ram(mr)) {
+        return NULL;
+    }
+    return mr->rdm;
+}
+
+void memory_region_set_ram_discard_manager(MemoryRegion *mr,
+                                           RamDiscardManager *rdm)
+{
+    g_assert(memory_region_is_ram(mr) && !memory_region_is_mapped(mr));
+    g_assert(!rdm || !mr->rdm);
+    mr->rdm = rdm;
+}
+
+uint64_t ram_discard_manager_get_min_granularity(const RamDiscardManager *rdm,
+                                                 const MemoryRegion *mr)
+{
+    RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_GET_CLASS(rdm);
+
+    g_assert(rdmc->get_min_granularity);
+    return rdmc->get_min_granularity(rdm, mr);
+}
+
+bool ram_discard_manager_is_populated(const RamDiscardManager *rdm,
+                                      const MemoryRegionSection *section)
+{
+    RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_GET_CLASS(rdm);
+
+    g_assert(rdmc->is_populated);
+    return rdmc->is_populated(rdm, section);
+}
+
+int ram_discard_manager_replay_populated(const RamDiscardManager *rdm,
+                                         MemoryRegionSection *section,
+                                         ReplayRamPopulate replay_fn,
+                                         void *opaque)
+{
+    RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_GET_CLASS(rdm);
+
+    g_assert(rdmc->replay_populated);
+    return rdmc->replay_populated(rdm, section, replay_fn, opaque);
+}
+
+void ram_discard_manager_register_listener(RamDiscardManager *rdm,
+                                           RamDiscardListener *rdl,
+                                           MemoryRegionSection *section)
+{
+    RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_GET_CLASS(rdm);
+
+    g_assert(rdmc->register_listener);
+    rdmc->register_listener(rdm, rdl, section);
+}
+
+void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
+                                             RamDiscardListener *rdl)
+{
+    RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_GET_CLASS(rdm);
+
+    g_assert(rdmc->unregister_listener);
+    rdmc->unregister_listener(rdm, rdl);
+}
+
 void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
 {
     uint8_t mask = 1 << client;
@@ -3310,10 +3374,17 @@ static const TypeInfo iommu_memory_region_info = {
     .abstract           = true,
 };
 
+static const TypeInfo ram_discard_manager_info = {
+    .parent             = TYPE_INTERFACE,
+    .name               = TYPE_RAM_DISCARD_MANAGER,
+    .class_size         = sizeof(RamDiscardManagerClass),
+};
+
 static void memory_register_types(void)
 {
     type_register_static(&memory_region_info);
     type_register_static(&iommu_memory_region_info);
+    type_register_static(&ram_discard_manager_info);
 }
 
 type_init(memory_register_types)
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 02/13] memory: Helpers to copy/free a MemoryRegionSection
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 01/13] memory: Introduce RamDiscardManager for RAM memory regions David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 03/13] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
                   ` (10 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

In case one wants to create a permanent copy of a MemoryRegionSections,
one needs access to flatview_ref()/flatview_unref(). Instead of exposing
these, let's just add helpers to copy/free a MemoryRegionSection and
properly adjust references.

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 | 20 ++++++++++++++++++++
 softmmu/memory.c      | 27 +++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 38a3b41ac1..e806d0140e 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1047,6 +1047,26 @@ static inline bool MemoryRegionSection_eq(MemoryRegionSection *a,
            a->nonvolatile == b->nonvolatile;
 }
 
+/**
+ * memory_region_section_new_copy: Copy a memory region section
+ *
+ * Allocate memory for a new copy, copy the memory region section, and
+ * properly take a reference on all relevant members.
+ *
+ * @s: the #MemoryRegionSection to copy
+ */
+MemoryRegionSection *memory_region_section_new_copy(MemoryRegionSection *s);
+
+/**
+ * memory_region_section_new_copy: Free a copied memory region section
+ *
+ * Free a copy of a memory section created via memory_region_section_new_copy().
+ * properly dropping references on all relevant members.
+ *
+ * @s: the #MemoryRegionSection to copy
+ */
+void memory_region_section_free_copy(MemoryRegionSection *s);
+
 /**
  * memory_region_init: Initialize a memory region
  *
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 26ea87d77a..776c7cac38 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2694,6 +2694,33 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
     return ret;
 }
 
+MemoryRegionSection *memory_region_section_new_copy(MemoryRegionSection *s)
+{
+    MemoryRegionSection *tmp = g_new(MemoryRegionSection, 1);
+
+    *tmp = *s;
+    if (tmp->mr) {
+        memory_region_ref(tmp->mr);
+    }
+    if (tmp->fv) {
+        bool ret  = flatview_ref(tmp->fv);
+
+        g_assert(ret);
+    }
+    return tmp;
+}
+
+void memory_region_section_free_copy(MemoryRegionSection *s)
+{
+    if (s->fv) {
+        flatview_unref(s->fv);
+    }
+    if (s->mr) {
+        memory_region_unref(s->mr);
+    }
+    g_free(s);
+}
+
 bool memory_region_present(MemoryRegion *container, hwaddr addr)
 {
     MemoryRegion *mr;
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 03/13] virtio-mem: Factor out traversing unplugged ranges
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 01/13] memory: Introduce RamDiscardManager for RAM memory regions David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 02/13] memory: Helpers to copy/free a MemoryRegionSection David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 04/13] virtio-mem: Don't report errors when ram_block_discard_range() fails David Hildenbrand
                   ` (9 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Alex Williamson, Peter Xu, Dr . David Alan Gilbert, Auger Eric,
	Pankaj Gupta, teawater, Igor Mammedov, Paolo Bonzini,
	Marek Kedzierski

Let's factor out the core logic, no need to replicate.

Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@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>
---
 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)
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 04/13] virtio-mem: Don't report errors when ram_block_discard_range() fails
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (2 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 03/13] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 05/13] virtio-mem: Implement RamDiscardManager interface David Hildenbrand
                   ` (8 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S. Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

Any errors are unexpected and ram_block_discard_range() already properly
prints errors. Let's stop manually reporting errors.

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 | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 471e464171..bbe42ad83b 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -246,17 +246,14 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
                                       uint64_t size, bool plug)
 {
     const uint64_t offset = start_gpa - vmem->addr;
-    int ret;
+    RAMBlock *rb = vmem->memdev->mr.ram_block;
 
     if (virtio_mem_is_busy()) {
         return -EBUSY;
     }
 
     if (!plug) {
-        ret = ram_block_discard_range(vmem->memdev->mr.ram_block, offset, size);
-        if (ret) {
-            error_report("Unexpected error discarding RAM: %s",
-                         strerror(-ret));
+        if (ram_block_discard_range(rb, offset, size)) {
             return -EBUSY;
         }
     }
@@ -345,15 +342,12 @@ static void virtio_mem_resize_usable_region(VirtIOMEM *vmem,
 static int virtio_mem_unplug_all(VirtIOMEM *vmem)
 {
     RAMBlock *rb = vmem->memdev->mr.ram_block;
-    int ret;
 
     if (virtio_mem_is_busy()) {
         return -EBUSY;
     }
 
-    ret = ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb));
-    if (ret) {
-        error_report("Unexpected error discarding RAM: %s", strerror(-ret));
+    if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
         return -EBUSY;
     }
     bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
@@ -625,14 +619,8 @@ 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;
-    int ret;
 
-    ret = ram_block_discard_range(rb, offset, size);
-    if (ret) {
-        error_report("Unexpected error discarding RAM: %s", strerror(-ret));
-        return -EINVAL;
-    }
-    return 0;
+    return ram_block_discard_range(rb, offset, size) ? -EINVAL : 0;
 }
 
 static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 05/13] virtio-mem: Implement RamDiscardManager interface
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (3 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 04/13] virtio-mem: Don't report errors when ram_block_discard_range() fails David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 06/13] vfio: Support for RamDiscardManager in the !vIOMMU case David Hildenbrand
                   ` (7 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, 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.

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@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>
---
 hw/virtio/virtio-mem.c         | 288 ++++++++++++++++++++++++++++++++-
 include/hw/virtio/virtio-mem.h |   3 +
 2 files changed, 288 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index bbe42ad83b..e209b56057 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -172,7 +172,146 @@ 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,
+/*
+ * Adjust the memory section to cover the intersection with the given range.
+ *
+ * Returns false if the intersection is empty, otherwise returns true.
+ */
+static bool virito_mem_intersect_memory_section(MemoryRegionSection *s,
+                                                uint64_t offset, uint64_t size)
+{
+    uint64_t start = MAX(s->offset_within_region, offset);
+    uint64_t end = MIN(s->offset_within_region + int128_get64(s->size),
+                       offset + size);
+
+    if (end <= start) {
+        return false;
+    }
+
+    s->offset_within_address_space += start - s->offset_within_region;
+    s->offset_within_region = start;
+    s->size = int128_make64(end - start);
+    return true;
+}
+
+typedef int (*virtio_mem_section_cb)(MemoryRegionSection *s, void *arg);
+
+static int virtio_mem_for_each_plugged_section(const VirtIOMEM *vmem,
+                                               MemoryRegionSection *s,
+                                               void *arg,
+                                               virtio_mem_section_cb cb)
+{
+    unsigned long first_bit, last_bit;
+    uint64_t offset, size;
+    int ret = 0;
+
+    first_bit = s->offset_within_region / vmem->bitmap_size;
+    first_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size, first_bit);
+    while (first_bit < vmem->bitmap_size) {
+        MemoryRegionSection tmp = *s;
+
+        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;
+
+        if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
+            break;
+        }
+        ret = cb(&tmp, arg);
+        if (ret) {
+            break;
+        }
+        first_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
+                                  last_bit + 2);
+    }
+    return ret;
+}
+
+static int virtio_mem_notify_populate_cb(MemoryRegionSection *s, void *arg)
+{
+    RamDiscardListener *rdl = arg;
+
+    return rdl->notify_populate(rdl, s);
+}
+
+static int virtio_mem_notify_discard_cb(MemoryRegionSection *s, void *arg)
+{
+    RamDiscardListener *rdl = arg;
+
+    rdl->notify_discard(rdl, s);
+    return 0;
+}
+
+static void virtio_mem_notify_unplug(VirtIOMEM *vmem, uint64_t offset,
+                                     uint64_t size)
+{
+    RamDiscardListener *rdl;
+
+    QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+        MemoryRegionSection tmp = *rdl->section;
+
+        if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
+            continue;
+        }
+        rdl->notify_discard(rdl, &tmp);
+    }
+}
+
+static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
+                                  uint64_t size)
+{
+    RamDiscardListener *rdl, *rdl2;
+    int ret = 0;
+
+    QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+        MemoryRegionSection tmp = *rdl->section;
+
+        if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
+            continue;
+        }
+        ret = rdl->notify_populate(rdl, &tmp);
+        if (ret) {
+            break;
+        }
+    }
+
+    if (ret) {
+        /* Notify all already-notified listeners. */
+        QLIST_FOREACH(rdl2, &vmem->rdl_list, next) {
+            MemoryRegionSection tmp = *rdl->section;
+
+            if (rdl2 == rdl) {
+                break;
+            }
+            if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
+                continue;
+            }
+            rdl2->notify_discard(rdl2, &tmp);
+        }
+    }
+    return ret;
+}
+
+static void virtio_mem_notify_unplug_all(VirtIOMEM *vmem)
+{
+    RamDiscardListener *rdl;
+
+    if (!vmem->size) {
+        return;
+    }
+
+    QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+        if (rdl->double_discard_supported) {
+            rdl->notify_discard(rdl, rdl->section);
+        } else {
+            virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
+                                                virtio_mem_notify_discard_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 +364,8 @@ 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;
@@ -256,6 +396,11 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
         if (ram_block_discard_range(rb, offset, size)) {
             return -EBUSY;
         }
+        virtio_mem_notify_unplug(vmem, offset, size);
+    } else if (virtio_mem_notify_plug(vmem, offset, size)) {
+        /* Could be a mapping attempt resulted in memory getting populated. */
+        ram_block_discard_range(vmem->memdev->mr.ram_block, offset, size);
+        return -EBUSY;
     }
     virtio_mem_set_bitmap(vmem, start_gpa, size, plug);
     return 0;
@@ -350,6 +495,8 @@ static int virtio_mem_unplug_all(VirtIOMEM *vmem)
     if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
         return -EBUSY;
     }
+    virtio_mem_notify_unplug_all(vmem);
+
     bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
     if (vmem->size) {
         vmem->size = 0;
@@ -598,6 +745,13 @@ 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 RamDiscardManager before the plug handler maps the
+     * memory region and exposes it via an address space.
+     */
+    memory_region_set_ram_discard_manager(&vmem->memdev->mr,
+                                          RAM_DISCARD_MANAGER(vmem));
 }
 
 static void virtio_mem_device_unrealize(DeviceState *dev)
@@ -605,6 +759,11 @@ 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_manager(&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));
@@ -632,11 +791,27 @@ static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
 
 static int virtio_mem_post_load(void *opaque, int version_id)
 {
+    VirtIOMEM *vmem = VIRTIO_MEM(opaque);
+    RamDiscardListener *rdl;
+    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.
+     */
+    QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
+        ret = virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
+                                                 virtio_mem_notify_populate_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 {
@@ -921,6 +1096,7 @@ 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);
@@ -940,11 +1116,107 @@ static Property virtio_mem_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static uint64_t virtio_mem_rdm_get_min_granularity(const RamDiscardManager *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 RamDiscardManager *rdm,
+                                        const MemoryRegionSection *s)
+{
+    const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+    uint64_t start_gpa = vmem->addr + s->offset_within_region;
+    uint64_t end_gpa = start_gpa + int128_get64(s->size);
+
+    g_assert(s->mr == &vmem->memdev->mr);
+
+    start_gpa = QEMU_ALIGN_DOWN(start_gpa, vmem->block_size);
+    end_gpa = QEMU_ALIGN_UP(end_gpa, vmem->block_size);
+
+    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);
+}
+
+struct VirtIOMEMReplayData {
+    void *fn;
+    void *opaque;
+};
+
+static int virtio_mem_rdm_replay_populated_cb(MemoryRegionSection *s, void *arg)
+{
+    struct VirtIOMEMReplayData *data = arg;
+
+    return ((ReplayRamPopulate)data->fn)(s, data->opaque);
+}
+
+static int virtio_mem_rdm_replay_populated(const RamDiscardManager *rdm,
+                                           MemoryRegionSection *s,
+                                           ReplayRamPopulate replay_fn,
+                                           void *opaque)
+{
+    const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+    struct VirtIOMEMReplayData data = {
+        .fn = replay_fn,
+        .opaque = opaque,
+    };
+
+    g_assert(s->mr == &vmem->memdev->mr);
+    return virtio_mem_for_each_plugged_section(vmem, s, &data,
+                                            virtio_mem_rdm_replay_populated_cb);
+}
+
+static void virtio_mem_rdm_register_listener(RamDiscardManager *rdm,
+                                             RamDiscardListener *rdl,
+                                             MemoryRegionSection *s)
+{
+    VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+    int ret;
+
+    g_assert(s->mr == &vmem->memdev->mr);
+    rdl->section = memory_region_section_new_copy(s);
+
+    QLIST_INSERT_HEAD(&vmem->rdl_list, rdl, next);
+    ret = virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
+                                              virtio_mem_notify_populate_cb);
+    if (ret) {
+        error_report("%s: Replaying plugged ranges failed: %s", __func__,
+                     strerror(-ret));
+    }
+}
+
+static void virtio_mem_rdm_unregister_listener(RamDiscardManager *rdm,
+                                               RamDiscardListener *rdl)
+{
+    VirtIOMEM *vmem = VIRTIO_MEM(rdm);
+
+    g_assert(rdl->section->mr == &vmem->memdev->mr);
+    if (vmem->size) {
+        if (rdl->double_discard_supported) {
+            rdl->notify_discard(rdl, rdl->section);
+        } else {
+            virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
+                                                virtio_mem_notify_discard_cb);
+        }
+    }
+
+    memory_region_section_free_copy(rdl->section);
+    rdl->section = NULL;
+    QLIST_REMOVE(rdl, next);
+}
+
 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);
+    RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_CLASS(klass);
 
     device_class_set_props(dc, virtio_mem_properties);
     dc->vmsd = &vmstate_virtio_mem;
@@ -960,6 +1232,12 @@ 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->replay_populated = virtio_mem_rdm_replay_populated;
+    rdmc->register_listener = virtio_mem_rdm_register_listener;
+    rdmc->unregister_listener = virtio_mem_rdm_unregister_listener;
 }
 
 static const TypeInfo virtio_mem_info = {
@@ -969,6 +1247,10 @@ 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_MANAGER },
+        { }
+    },
 };
 
 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 {
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 06/13] vfio: Support for RamDiscardManager in the !vIOMMU case
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (4 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 05/13] virtio-mem: Implement RamDiscardManager interface David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 07/13] vfio: Query and store the maximum number of possible DMA mappings David Hildenbrand
                   ` (6 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

Implement support for RamDiscardManager, 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.

Using virtio-mem with vfio is still blocked via
ram_block_discard_disable()/ram_block_discard_require() after this patch.

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 hw/vfio/common.c              | 164 ++++++++++++++++++++++++++++++++++
 include/hw/vfio/vfio-common.h |  11 +++
 2 files changed, 175 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index ae5654fcdb..5af7755227 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -649,6 +649,110 @@ out:
     rcu_read_unlock();
 }
 
+static void vfio_ram_discard_notify_discard(RamDiscardListener *rdl,
+                                            MemoryRegionSection *section)
+{
+    VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener,
+                                                listener);
+    const hwaddr size = int128_get64(section->size);
+    const hwaddr iova = section->offset_within_address_space;
+    int ret;
+
+    /* Unmap with a single call. */
+    ret = vfio_dma_unmap(vrdl->container, iova, size , NULL);
+    if (ret) {
+        error_report("%s: vfio_dma_unmap() failed: %s", __func__,
+                     strerror(-ret));
+    }
+}
+
+static int vfio_ram_discard_notify_populate(RamDiscardListener *rdl,
+                                            MemoryRegionSection *section)
+{
+    VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener,
+                                                listener);
+    const hwaddr end = section->offset_within_region +
+                       int128_get64(section->size);
+    hwaddr start, next, iova;
+    void *vaddr;
+    int ret;
+
+    /*
+     * Map in (aligned within memory region) minimum granularity, so we can
+     * unmap in minimum granularity later.
+     */
+    for (start = section->offset_within_region; start < end; start = next) {
+        next = ROUND_UP(start + 1, vrdl->granularity);
+        next = MIN(next, end);
+
+        iova = start - section->offset_within_region +
+               section->offset_within_address_space;
+        vaddr = memory_region_get_ram_ptr(section->mr) + start;
+
+        ret = vfio_dma_map(vrdl->container, iova, next - start,
+                           vaddr, section->readonly);
+        if (ret) {
+            /* Rollback */
+            vfio_ram_discard_notify_discard(rdl, section);
+            return ret;
+        }
+    }
+    return 0;
+}
+
+static void vfio_register_ram_discard_listener(VFIOContainer *container,
+                                               MemoryRegionSection *section)
+{
+    RamDiscardManager *rdm = memory_region_get_ram_discard_manager(section->mr);
+    VFIORamDiscardListener *vrdl;
+
+    /* Ignore some corner cases not relevant in practice. */
+    g_assert(QEMU_IS_ALIGNED(section->offset_within_region, TARGET_PAGE_SIZE));
+    g_assert(QEMU_IS_ALIGNED(section->offset_within_address_space,
+                             TARGET_PAGE_SIZE));
+    g_assert(QEMU_IS_ALIGNED(int128_get64(section->size), TARGET_PAGE_SIZE));
+
+    vrdl = g_new0(VFIORamDiscardListener, 1);
+    vrdl->container = container;
+    vrdl->mr = section->mr;
+    vrdl->offset_within_address_space = section->offset_within_address_space;
+    vrdl->size = int128_get64(section->size);
+    vrdl->granularity = ram_discard_manager_get_min_granularity(rdm,
+                                                                section->mr);
+
+    g_assert(vrdl->granularity && is_power_of_2(vrdl->granularity));
+    g_assert(vrdl->granularity >= 1 << ctz64(container->pgsizes));
+
+    ram_discard_listener_init(&vrdl->listener,
+                              vfio_ram_discard_notify_populate,
+                              vfio_ram_discard_notify_discard, true);
+    ram_discard_manager_register_listener(rdm, &vrdl->listener, section);
+    QLIST_INSERT_HEAD(&container->vrdl_list, vrdl, next);
+}
+
+static void vfio_unregister_ram_discard_listener(VFIOContainer *container,
+                                                 MemoryRegionSection *section)
+{
+    RamDiscardManager *rdm = memory_region_get_ram_discard_manager(section->mr);
+    VFIORamDiscardListener *vrdl = NULL;
+
+    QLIST_FOREACH(vrdl, &container->vrdl_list, next) {
+        if (vrdl->mr == section->mr &&
+            vrdl->offset_within_address_space ==
+            section->offset_within_address_space) {
+            break;
+        }
+    }
+
+    if (!vrdl) {
+        hw_error("vfio: Trying to unregister missing RAM discard listener");
+    }
+
+    ram_discard_manager_unregister_listener(rdm, &vrdl->listener);
+    QLIST_REMOVE(vrdl, next);
+    g_free(vrdl);
+}
+
 static void vfio_listener_region_add(MemoryListener *listener,
                                      MemoryRegionSection *section)
 {
@@ -810,6 +914,16 @@ 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 RamDiscardManager, we only want to map the
+     * actually populated parts - and update the mapping whenever we're notified
+     * about changes.
+     */
+    if (memory_region_has_ram_discard_manager(section->mr)) {
+        vfio_register_ram_discard_listener(container, section);
+        return;
+    }
+
     vaddr = memory_region_get_ram_ptr(section->mr) +
             section->offset_within_region +
             (iova - section->offset_within_address_space);
@@ -947,6 +1061,10 @@ 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_manager(section->mr)) {
+        vfio_unregister_ram_discard_listener(container, section);
+        /* Unregistering will trigger an unmap. */
+        try_unmap = false;
     }
 
     if (try_unmap) {
@@ -1108,6 +1226,49 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
     rcu_read_unlock();
 }
 
+static int vfio_ram_discard_get_dirty_bitmap(MemoryRegionSection *section,
+                                             void *opaque)
+{
+    const hwaddr size = int128_get64(section->size);
+    const hwaddr iova = section->offset_within_address_space;
+    const ram_addr_t ram_addr = memory_region_get_ram_addr(section->mr) +
+                                section->offset_within_region;
+    VFIORamDiscardListener *vrdl = opaque;
+
+    /*
+     * Sync the whole mapped region (spanning multiple individual mappings)
+     * in one go.
+     */
+    return vfio_get_dirty_bitmap(vrdl->container, iova, size, ram_addr);
+}
+
+static int vfio_sync_ram_discard_listener_dirty_bitmap(VFIOContainer *container,
+                                                   MemoryRegionSection *section)
+{
+    RamDiscardManager *rdm = memory_region_get_ram_discard_manager(section->mr);
+    VFIORamDiscardListener *vrdl = NULL;
+
+    QLIST_FOREACH(vrdl, &container->vrdl_list, next) {
+        if (vrdl->mr == section->mr &&
+            vrdl->offset_within_address_space ==
+            section->offset_within_address_space) {
+            break;
+        }
+    }
+
+    if (!vrdl) {
+        hw_error("vfio: Trying to sync missing RAM discard listener");
+    }
+
+    /*
+     * We only want/can synchronize the bitmap for actually mapped parts -
+     * which correspond to populated parts. Replay all populated parts.
+     */
+    return ram_discard_manager_replay_populated(rdm, section,
+                                              vfio_ram_discard_get_dirty_bitmap,
+                                                &vrdl);
+}
+
 static int vfio_sync_dirty_bitmap(VFIOContainer *container,
                                   MemoryRegionSection *section)
 {
@@ -1139,6 +1300,8 @@ static int vfio_sync_dirty_bitmap(VFIOContainer *container,
             }
         }
         return 0;
+    } else if (memory_region_has_ram_discard_manager(section->mr)) {
+        return vfio_sync_ram_discard_listener_dirty_bitmap(container, section);
     }
 
     ram_addr = memory_region_get_ram_addr(section->mr) +
@@ -1770,6 +1933,7 @@ 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 6141162d7a..681432213d 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 +103,16 @@ typedef struct VFIOGuestIOMMU {
     QLIST_ENTRY(VFIOGuestIOMMU) giommu_next;
 } VFIOGuestIOMMU;
 
+typedef struct VFIORamDiscardListener {
+    VFIOContainer *container;
+    MemoryRegion *mr;
+    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;
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 07/13] vfio: Query and store the maximum number of possible DMA mappings
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (5 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 06/13] vfio: Support for RamDiscardManager in the !vIOMMU case David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 08/13] vfio: Sanity check maximum number of DMA mappings with RamDiscardManager David Hildenbrand
                   ` (5 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

Let's query the maximum number of possible DMA mappings by querying the
available mappings when creating the container (before any mappings are
created). We'll use this informaton soon to perform some sanity checks
and warn the user.

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 hw/vfio/common.c              | 4 ++++
 include/hw/vfio/vfio-common.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5af7755227..79628d60ae 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1931,6 +1931,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
     container->fd = fd;
     container->error = NULL;
     container->dirty_pages_supported = false;
+    container->dma_max_mappings = 0;
     QLIST_INIT(&container->giommu_list);
     QLIST_INIT(&container->hostwin_list);
     QLIST_INIT(&container->vrdl_list);
@@ -1962,7 +1963,10 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
         vfio_host_win_add(container, 0, (hwaddr)-1, info->iova_pgsizes);
         container->pgsizes = info->iova_pgsizes;
 
+        /* The default in the kernel ("dma_entry_limit") is 65535. */
+        container->dma_max_mappings = 65535;
         if (!ret) {
+            vfio_get_info_dma_avail(info, &container->dma_max_mappings);
             vfio_get_iommu_info_migration(container, info);
         }
         g_free(info);
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 681432213d..8af11b0a76 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -88,6 +88,7 @@ typedef struct VFIOContainer {
     uint64_t dirty_pgsizes;
     uint64_t max_dirty_bitmap_size;
     unsigned long pgsizes;
+    unsigned int dma_max_mappings;
     QLIST_HEAD(, VFIOGuestIOMMU) giommu_list;
     QLIST_HEAD(, VFIOHostDMAWindow) hostwin_list;
     QLIST_HEAD(, VFIOGroup) group_list;
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 08/13] vfio: Sanity check maximum number of DMA mappings with RamDiscardManager
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (6 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 07/13] vfio: Query and store the maximum number of possible DMA mappings David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 09/13] vfio: Support for RamDiscardManager in the vIOMMU case David Hildenbrand
                   ` (4 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

Although RamDiscardManager can handle running into the maximum number of
DMA mappings by propagating errors when creating a DMA mapping, we want
to sanity check and warn the user early that there is a theoretical setup
issue and that virtio-mem might not be able to provide as much memory
towards a VM as desired.

As suggested by Alex, let's use the number of KVM memory slots to guess
how many other mappings we might see over time.

Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 hw/vfio/common.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 79628d60ae..f8a2fe8441 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -728,6 +728,49 @@ static void vfio_register_ram_discard_listener(VFIOContainer *container,
                               vfio_ram_discard_notify_discard, true);
     ram_discard_manager_register_listener(rdm, &vrdl->listener, section);
     QLIST_INSERT_HEAD(&container->vrdl_list, vrdl, next);
+
+    /*
+     * Sanity-check if we have a theoretically problematic setup where we could
+     * exceed the maximum number of possible DMA mappings over time. We assume
+     * that each mapped section in the same address space as a RamDiscardManager
+     * section consumes exactly one DMA mapping, with the exception of
+     * RamDiscardManager sections; i.e., we don't expect to have gIOMMU sections
+     * in the same address space as RamDiscardManager sections.
+     *
+     * We assume that each section in the address space consumes one memslot.
+     * We take the number of KVM memory slots as a best guess for the maximum
+     * number of sections in the address space we could have over time,
+     * also consuming DMA mappings.
+     */
+    if (container->dma_max_mappings) {
+        unsigned int vrdl_count = 0, vrdl_mappings = 0, max_memslots = 512;
+
+#ifdef CONFIG_KVM
+        if (kvm_enabled()) {
+            max_memslots = kvm_get_max_memslots();
+        }
+#endif
+
+        QLIST_FOREACH(vrdl, &container->vrdl_list, next) {
+            hwaddr start, end;
+
+            start = QEMU_ALIGN_DOWN(vrdl->offset_within_address_space,
+                                    vrdl->granularity);
+            end = ROUND_UP(vrdl->offset_within_address_space + vrdl->size,
+                           vrdl->granularity);
+            vrdl_mappings += (end - start) / vrdl->granularity;
+            vrdl_count++;
+        }
+
+        if (vrdl_mappings + max_memslots - vrdl_count >
+            container->dma_max_mappings) {
+            warn_report("%s: possibly running out of DMA mappings. E.g., try"
+                        " increasing the 'block-size' of virtio-mem devies."
+                        " Maximum possible DMA mappings: %d, Maximum possible"
+                        " memslots: %d", __func__, container->dma_max_mappings,
+                        max_memslots);
+        }
+    }
 }
 
 static void vfio_unregister_ram_discard_listener(VFIOContainer *container,
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 09/13] vfio: Support for RamDiscardManager in the vIOMMU case
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (7 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 08/13] vfio: Sanity check maximum number of DMA mappings with RamDiscardManager David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 10/13] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
                   ` (3 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

vIOMMU support works already with RamDiscardManager 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, RamDiscardManager
implementations might not be back up and running yet: let's add runstate
priorities to enforce the order when restoring.

Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 hw/vfio/common.c            | 39 +++++++++++++++++++++++++++++++++++++
 hw/virtio/virtio-mem.c      |  1 +
 include/migration/vmstate.h |  1 +
 3 files changed, 41 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index f8a2fe8441..8a9bbf2791 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -36,6 +36,7 @@
 #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"
@@ -569,6 +570,44 @@ 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_manager(mr)) {
+        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
+        MemoryRegionSection tmp = {
+            .mr = mr,
+            .offset_within_region = xlat,
+            .size = int128_make64(len),
+        };
+
+        /*
+         * Malicious VMs can map memory into the IOMMU, which is expected
+         * to remain discarded. vfio will pin all pages, populating memory.
+         * Disallow that. vmstate priorities make sure any RamDiscardManager
+         * were already restored before IOMMUs are restored.
+         */
+        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
+            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.");
     }
 
     /*
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index e209b56057..cbd07fc9f1 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -886,6 +886,7 @@ static const VMStateDescription vmstate_virtio_mem_device = {
     .name = "virtio-mem-device",
     .minimum_version_id = 1,
     .version_id = 1,
+    .priority = MIG_PRI_VIRTIO_MEM,
     .post_load = virtio_mem_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_WITH_TMP(VirtIOMEM, VirtIOMEMMigSanityChecks,
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 075ee80096..3bf58ff043 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -153,6 +153,7 @@ typedef enum {
     MIG_PRI_DEFAULT = 0,
     MIG_PRI_IOMMU,              /* Must happen before PCI devices */
     MIG_PRI_PCI_BUS,            /* Must happen before IOMMU */
+    MIG_PRI_VIRTIO_MEM,         /* Must happen before IOMMU */
     MIG_PRI_GICV3_ITS,          /* Must happen before PCI devices */
     MIG_PRI_GICV3,              /* Must happen before the ITS */
     MIG_PRI_MAX,
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 10/13] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require)
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (8 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 09/13] vfio: Support for RamDiscardManager in the vIOMMU case David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 11/13] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
                   ` (2 subsequent siblings)
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Alex Williamson, Peter Xu, Dr . David Alan Gilbert, Auger Eric,
	Pankaj Gupta, 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>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Acked-by: Michael S. Tsirkin <mst@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 85034d9c11..aaa2b2eb92 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3647,56 +3647,64 @@ 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_required_cnt;
+static unsigned int ram_block_discard_disabled_cnt;
+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_disabled_cnt--;
+    } else if (!ram_block_discard_required_cnt) {
+        ram_block_discard_disabled_cnt++;
+    } 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_required_cnt--;
+    } else if (!ram_block_discard_disabled_cnt) {
+        ram_block_discard_required_cnt++;
+    } 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_disabled_cnt);
 }
 
 bool ram_block_discard_is_required(void)
 {
-    return qatomic_read(&ram_block_discard_disabled) < 0;
+    return qatomic_read(&ram_block_discard_required_cnt);
 }
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 11/13] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (9 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 10/13] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 12/13] virtio-mem: Require only coordinated discards David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 13/13] vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus David Hildenbrand
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Alex Williamson, Peter Xu, Dr . David Alan Gilbert, Auger Eric,
	Pankaj Gupta, 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 RamDiscardManager

Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 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 e806d0140e..bba7b6643e 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2873,6 +2873,12 @@ static inline MemOp devend_memop(enum device_endian end)
  */
 int ram_block_discard_disable(bool state);
 
+/*
+ * See ram_block_discard_disable(): only disable uncoordinated discards,
+ * keeping coordinated discards (via the RamDiscardManager) enabled.
+ */
+int ram_block_uncoordinated_discard_disable(bool state);
+
 /*
  * Inhibit technologies that disable discarding of pages in RAM blocks.
  *
@@ -2882,12 +2888,20 @@ 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
+ * RamDiscardManager).
+ */
+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 aaa2b2eb92..ead7b5c429 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3647,8 +3647,14 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root)
     }
 }
 
+/* Require any discards to work. */
 static unsigned int ram_block_discard_required_cnt;
+/* Require only coordinated discards to work. */
+static unsigned int ram_block_coordinated_discard_required_cnt;
+/* Disable any discards. */
 static unsigned int ram_block_discard_disabled_cnt;
+/* Disable only uncoordinated discards. */
+static unsigned int ram_block_uncoordinated_discard_disabled_cnt;
 static QemuMutex ram_block_discard_disable_mutex;
 
 static void ram_block_discard_disable_mutex_lock(void)
@@ -3674,10 +3680,27 @@ int ram_block_discard_disable(bool state)
     ram_block_discard_disable_mutex_lock();
     if (!state) {
         ram_block_discard_disabled_cnt--;
-    } else if (!ram_block_discard_required_cnt) {
-        ram_block_discard_disabled_cnt++;
+    } else if (ram_block_discard_required_cnt ||
+               ram_block_coordinated_discard_required_cnt) {
+        ret = -EBUSY;
     } else {
+        ram_block_discard_disabled_cnt++;
+    }
+    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_disabled_cnt--;
+    } else if (ram_block_discard_required_cnt) {
         ret = -EBUSY;
+    } else {
+        ram_block_uncoordinated_discard_disabled_cnt++;
     }
     ram_block_discard_disable_mutex_unlock();
     return ret;
@@ -3690,10 +3713,27 @@ int ram_block_discard_require(bool state)
     ram_block_discard_disable_mutex_lock();
     if (!state) {
         ram_block_discard_required_cnt--;
-    } else if (!ram_block_discard_disabled_cnt) {
-        ram_block_discard_required_cnt++;
+    } else if (ram_block_discard_disabled_cnt ||
+               ram_block_uncoordinated_discard_disabled_cnt) {
+        ret = -EBUSY;
     } else {
+        ram_block_discard_required_cnt++;
+    }
+    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_required_cnt--;
+    } else if (ram_block_discard_disabled_cnt) {
         ret = -EBUSY;
+    } else {
+        ram_block_coordinated_discard_required_cnt++;
     }
     ram_block_discard_disable_mutex_unlock();
     return ret;
@@ -3701,10 +3741,12 @@ int ram_block_discard_require(bool state)
 
 bool ram_block_discard_is_disabled(void)
 {
-    return qatomic_read(&ram_block_discard_disabled_cnt);
+    return qatomic_read(&ram_block_discard_disabled_cnt) ||
+           qatomic_read(&ram_block_uncoordinated_discard_disabled_cnt);
 }
 
 bool ram_block_discard_is_required(void)
 {
-    return qatomic_read(&ram_block_discard_required_cnt);
+    return qatomic_read(&ram_block_discard_required_cnt) ||
+           qatomic_read(&ram_block_coordinated_discard_required_cnt);
 }
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 12/13] virtio-mem: Require only coordinated discards
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (10 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 11/13] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  2021-04-13  9:55 ` [PATCH RESEND v7 13/13] vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus David Hildenbrand
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Alex Williamson, Peter Xu, Dr . David Alan Gilbert, Auger Eric,
	Pankaj Gupta, teawater, Igor Mammedov, Paolo Bonzini,
	Marek Kedzierski

We implement the RamDiscardManager interface and only require coordinated
discarding of RAM to work.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@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>
---
 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 cbd07fc9f1..9e79b5b50c 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -719,7 +719,7 @@ 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;
     }
@@ -727,7 +727,7 @@ 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;
     }
 
@@ -771,7 +771,7 @@ 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,
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

* [PATCH RESEND v7 13/13] vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus
  2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
                   ` (11 preceding siblings ...)
  2021-04-13  9:55 ` [PATCH RESEND v7 12/13] virtio-mem: Require only coordinated discards David Hildenbrand
@ 2021-04-13  9:55 ` David Hildenbrand
  12 siblings, 0 replies; 14+ messages in thread
From: David Hildenbrand @ 2021-04-13  9:55 UTC (permalink / raw)
  To: qemu-devel
  Cc: Pankaj Gupta, Wei Yang, Michael S . Tsirkin, David Hildenbrand,
	Dr . David Alan Gilbert, Peter Xu, Auger Eric, Alex Williamson,
	teawater, Igor Mammedov, Paolo Bonzini, Marek Kedzierski

We support coordinated discarding of RAM using the RamDiscardManager for
the VFIO_TYPE1 iommus. Let's unlock support for coordinated discards,
keeping uncoordinated discards (e.g., via virtio-balloon) disabled if
possible.

This unlocks virtio-mem + vfio on x86-64. Note that vfio used via "nvme://"
by the block layer has to be implemented/unlocked separately. For now,
virtio-mem only supports x86-64; we don't restrict RamDiscardManager to
x86-64, though: arm64 and s390x are supposed to work as well, and we'll
test once unlocking virtio-mem support. The spapr IOMMUs will need special
care, to be tackled later, e.g.., once supporting virtio-mem.

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).

Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@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>
---
 hw/vfio/common.c | 65 +++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 53 insertions(+), 12 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 8a9bbf2791..3f0d111360 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -135,6 +135,29 @@ static const char *index_to_str(VFIODevice *vbasedev, int index)
     }
 }
 
+static int vfio_ram_block_discard_disable(VFIOContainer *container, bool state)
+{
+    switch (container->iommu_type) {
+    case VFIO_TYPE1v2_IOMMU:
+    case VFIO_TYPE1_IOMMU:
+        /*
+         * We support coordinated discarding of RAM via the RamDiscardManager.
+         */
+        return ram_block_uncoordinated_discard_disable(state);
+    default:
+        /*
+         * VFIO_SPAPR_TCE_IOMMU most probably works just fine with
+         * RamDiscardManager, however, it is completely untested.
+         *
+         * VFIO_SPAPR_TCE_v2_IOMMU with "DMA memory preregistering" does
+         * completely the opposite of managing mapping/pinning dynamically as
+         * required by RamDiscardManager. We would have to special-case sections
+         * with a RamDiscardManager.
+         */
+        return ram_block_discard_disable(state);
+    }
+}
+
 int vfio_set_irq_signaling(VFIODevice *vbasedev, int index, int subindex,
                            int action, int fd, Error **errp)
 {
@@ -1977,15 +2000,25 @@ 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 RamDiscardManager
+     * with some IOMMU types. vfio_ram_block_discard_disable() handles the
+     * details once we know which type of IOMMU we are using.
      */
-    ret = ram_block_discard_disable(true);
-    if (ret) {
-        error_setg_errno(errp, -ret, "Cannot set discarding of RAM broken");
-        return ret;
-    }
 
     QLIST_FOREACH(container, &space->containers, next) {
         if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
+            ret = vfio_ram_block_discard_disable(container, true);
+            if (ret) {
+                error_setg_errno(errp, -ret,
+                                 "Cannot set discarding of RAM broken");
+                if (ioctl(group->fd, VFIO_GROUP_UNSET_CONTAINER,
+                          &container->fd)) {
+                    error_report("vfio: error disconnecting group %d from"
+                                 " container", group->groupid);
+                }
+                return ret;
+            }
             group->container = container;
             QLIST_INSERT_HEAD(&container->group_list, group, container_next);
             vfio_kvm_device_add_group(group);
@@ -2023,6 +2056,12 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
         goto free_container_exit;
     }
 
+    ret = vfio_ram_block_discard_disable(container, true);
+    if (ret) {
+        error_setg_errno(errp, -ret, "Cannot set discarding of RAM broken");
+        goto free_container_exit;
+    }
+
     switch (container->iommu_type) {
     case VFIO_TYPE1v2_IOMMU:
     case VFIO_TYPE1_IOMMU:
@@ -2070,7 +2109,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
             if (ret) {
                 error_setg_errno(errp, errno, "failed to enable container");
                 ret = -errno;
-                goto free_container_exit;
+                goto enable_discards_exit;
             }
         } else {
             container->prereg_listener = vfio_prereg_listener;
@@ -2082,7 +2121,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
                 ret = -1;
                 error_propagate_prepend(errp, container->error,
                     "RAM memory listener initialization failed: ");
-                goto free_container_exit;
+                goto enable_discards_exit;
             }
         }
 
@@ -2095,7 +2134,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
             if (v2) {
                 memory_listener_unregister(&container->prereg_listener);
             }
-            goto free_container_exit;
+            goto enable_discards_exit;
         }
 
         if (v2) {
@@ -2110,7 +2149,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
             if (ret) {
                 error_setg_errno(errp, -ret,
                                  "failed to remove existing window");
-                goto free_container_exit;
+                goto enable_discards_exit;
             }
         } else {
             /* The default table uses 4K pages */
@@ -2151,6 +2190,9 @@ listener_release_exit:
     vfio_kvm_device_del_group(group);
     vfio_listener_release(container);
 
+enable_discards_exit:
+    vfio_ram_block_discard_disable(container, false);
+
 free_container_exit:
     g_free(container);
 
@@ -2158,7 +2200,6 @@ close_fd_exit:
     close(fd);
 
 put_space_exit:
-    ram_block_discard_disable(false);
     vfio_put_address_space(space);
 
     return ret;
@@ -2280,7 +2321,7 @@ void vfio_put_group(VFIOGroup *group)
     }
 
     if (!group->ram_block_discard_allowed) {
-        ram_block_discard_disable(false);
+        vfio_ram_block_discard_disable(group->container, false);
     }
     vfio_kvm_device_del_group(group);
     vfio_disconnect_container(group);
@@ -2334,7 +2375,7 @@ 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);
+            vfio_ram_block_discard_disable(group->container, false);
         }
     }
 
-- 
2.30.2



^ permalink raw reply	[flat|nested] 14+ messages in thread

end of thread, other threads:[~2021-04-13 10:07 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-04-13  9:55 [PATCH RESEND v7 00/13] virtio-mem: vfio support David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 01/13] memory: Introduce RamDiscardManager for RAM memory regions David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 02/13] memory: Helpers to copy/free a MemoryRegionSection David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 03/13] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 04/13] virtio-mem: Don't report errors when ram_block_discard_range() fails David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 05/13] virtio-mem: Implement RamDiscardManager interface David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 06/13] vfio: Support for RamDiscardManager in the !vIOMMU case David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 07/13] vfio: Query and store the maximum number of possible DMA mappings David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 08/13] vfio: Sanity check maximum number of DMA mappings with RamDiscardManager David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 09/13] vfio: Support for RamDiscardManager in the vIOMMU case David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 10/13] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 11/13] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 12/13] virtio-mem: Require only coordinated discards David Hildenbrand
2021-04-13  9:55 ` [PATCH RESEND v7 13/13] vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus David Hildenbrand

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