Merge remote-tracking branch 'remotes/ehabkost-gl/tags/machine-next-pull-request' into staging

Machine queue, 2021-07-07

Deprecation:
* Deprecate pmem=on with non-DAX capable backend file
  (Igor Mammedov)

Feature:
* virtio-mem: vfio support (David Hildenbrand)

Cleanup:
* vmbus: Don't make QOM property registration conditional
  (Eduardo Habkost)

# gpg: Signature made Thu 08 Jul 2021 20:55:04 BST
# gpg:                using RSA key 5A322FD5ABC4D3DBACCFD1AA2807936F984DC5A6
# gpg:                issuer "ehabkost@redhat.com"
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>" [full]
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost-gl/tags/machine-next-pull-request:
  vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus
  virtio-mem: Require only coordinated discards
  softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types
  softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require)
  vfio: Support for RamDiscardManager in the vIOMMU case
  vfio: Sanity check maximum number of DMA mappings with RamDiscardManager
  vfio: Query and store the maximum number of possible DMA mappings
  vfio: Support for RamDiscardManager in the !vIOMMU case
  virtio-mem: Implement RamDiscardManager interface
  virtio-mem: Don't report errors when ram_block_discard_range() fails
  virtio-mem: Factor out traversing unplugged ranges
  memory: Helpers to copy/free a MemoryRegionSection
  memory: Introduce RamDiscardManager for RAM memory regions
  Deprecate pmem=on with non-DAX capable backend file
  vmbus: Don't make QOM property registration conditional

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

4 files changed, 316 insertions, 24 deletions

diff --git a/include/exec/memory.h b/include/exec/memory.h
index b116f7c..c3d417d 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.  */
@@ -448,6 +476,206 @@ 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;
 
@@ -494,6 +722,7 @@ struct MemoryRegion {
     const char *name;
     unsigned ioeventfd_nb;
     MemoryRegionIoeventfd *ioeventfds;
+    RamDiscardManager *rdm; /* Only for RAM */
 };
 
 struct IOMMUMemoryRegion {
@@ -825,28 +1054,6 @@ 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)
 {
@@ -860,6 +1067,26 @@ static inline bool MemoryRegionSection_eq(MemoryRegionSection *a,
 }
 
 /**
+ * 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
  *
  * The region typically acts as a container for other memory regions.  Use
@@ -2024,6 +2251,41 @@ 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
+ * @rdm: #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.
  *
@@ -2632,6 +2894,12 @@ 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.
  *
  * Returns 0 if successful. Returns -EBUSY if discards are already set to
@@ -2640,12 +2908,20 @@ 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/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 6141162..8af11b0 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -88,9 +88,11 @@ 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;
+    QLIST_HEAD(, VFIORamDiscardListener) vrdl_list;
     QLIST_ENTRY(VFIOContainer) next;
 } VFIOContainer;
 
@@ -102,6 +104,16 @@ 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;
diff --git a/include/hw/virtio/virtio-mem.h b/include/hw/virtio/virtio-mem.h
index 4eeb82d..9a6e348 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 {
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 8df7b69..017c036 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,