vfio/container: recover from unmap-all-vaddr failure

If there are multiple containers and unmap-all fails for some container, we
need to remap vaddr for the other containers for which unmap-all succeeded.
Recover by walking all address ranges of all containers to restore the vaddr
for each.  Do so by invoking the vfio listener callback, and passing a new
"remap" flag that tells it to restore a mapping without re-allocating new
userland data structures.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/1749569991-25171-9-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/cpr-legacy.c

@@ -29,6 +29,7 @@ static bool vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
         error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
         return false;
     }
+    container->cpr.vaddr_unmapped = true;
     return true;
 }
 
@@ -59,6 +60,14 @@ static int vfio_legacy_cpr_dma_map(const VFIOContainerBase *bcontainer,
     return 0;
 }
 
+static void vfio_region_remap(MemoryListener *listener,
+                              MemoryRegionSection *section)
+{
+    VFIOContainer *container = container_of(listener, VFIOContainer,
+                                            cpr.remap_listener);
+    vfio_container_region_add(&container->bcontainer, section, true);
+}
+
 static bool vfio_cpr_supported(VFIOContainer *container, Error **errp)
 {
     if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR)) {
@@ -120,6 +129,40 @@ static const VMStateDescription vfio_container_vmstate = {
     }
 };
 
+static int vfio_cpr_fail_notifier(NotifierWithReturn *notifier,
+                                  MigrationEvent *e, Error **errp)
+{
+    VFIOContainer *container =
+        container_of(notifier, VFIOContainer, cpr.transfer_notifier);
+    VFIOContainerBase *bcontainer = &container->bcontainer;
+
+    if (e->type != MIG_EVENT_PRECOPY_FAILED) {
+        return 0;
+    }
+
+    if (container->cpr.vaddr_unmapped) {
+        /*
+         * Force a call to vfio_region_remap for each mapped section by
+         * temporarily registering a listener, and temporarily diverting
+         * dma_map to vfio_legacy_cpr_dma_map.  The latter restores vaddr.
+         */
+
+        VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+        vioc->dma_map = vfio_legacy_cpr_dma_map;
+
+        container->cpr.remap_listener = (MemoryListener) {
+            .name = "vfio cpr recover",
+            .region_add = vfio_region_remap
+        };
+        memory_listener_register(&container->cpr.remap_listener,
+                                 bcontainer->space->as);
+        memory_listener_unregister(&container->cpr.remap_listener);
+        container->cpr.vaddr_unmapped = false;
+        vioc->dma_map = container->cpr.saved_dma_map;
+    }
+    return 0;
+}
+
 bool vfio_legacy_cpr_register_container(VFIOContainer *container, Error **errp)
 {
     VFIOContainerBase *bcontainer = &container->bcontainer;
@@ -142,6 +185,10 @@ bool vfio_legacy_cpr_register_container(VFIOContainer *container, Error **errp)
         container->cpr.saved_dma_map = vioc->dma_map;
         vioc->dma_map = vfio_legacy_cpr_dma_map;
     }
+
+    migration_add_notifier_mode(&container->cpr.transfer_notifier,
+                                vfio_cpr_fail_notifier,
+                                MIG_MODE_CPR_TRANSFER);
     return true;
 }
 
@@ -152,6 +199,50 @@ void vfio_legacy_cpr_unregister_container(VFIOContainer *container)
     migration_remove_notifier(&bcontainer->cpr_reboot_notifier);
     migrate_del_blocker(&container->cpr.blocker);
     vmstate_unregister(NULL, &vfio_container_vmstate, container);
+    migration_remove_notifier(&container->cpr.transfer_notifier);
+}
+
+/*
+ * In old QEMU, VFIO_DMA_UNMAP_FLAG_VADDR may fail on some mapping after
+ * succeeding for others, so the latter have lost their vaddr.  Call this
+ * to restore vaddr for a section with a giommu.
+ *
+ * The giommu already exists.  Find it and replay it, which calls
+ * vfio_legacy_cpr_dma_map further down the stack.
+ */
+void vfio_cpr_giommu_remap(VFIOContainerBase *bcontainer,
+                           MemoryRegionSection *section)
+{
+    VFIOGuestIOMMU *giommu = NULL;
+    hwaddr as_offset = section->offset_within_address_space;
+    hwaddr iommu_offset = as_offset - section->offset_within_region;
+
+    QLIST_FOREACH(giommu, &bcontainer->giommu_list, giommu_next) {
+        if (giommu->iommu_mr == IOMMU_MEMORY_REGION(section->mr) &&
+            giommu->iommu_offset == iommu_offset) {
+            break;
+        }
+    }
+    g_assert(giommu);
+    memory_region_iommu_replay(giommu->iommu_mr, &giommu->n);
+}
+
+/*
+ * In old QEMU, VFIO_DMA_UNMAP_FLAG_VADDR may fail on some mapping after
+ * succeeding for others, so the latter have lost their vaddr.  Call this
+ * to restore vaddr for a section with a RamDiscardManager.
+ *
+ * The ram discard listener already exists.  Call its populate function
+ * directly, which calls vfio_legacy_cpr_dma_map.
+ */
+bool vfio_cpr_ram_discard_register_listener(VFIOContainerBase *bcontainer,
+                                            MemoryRegionSection *section)
+{
+    VFIORamDiscardListener *vrdl =
+        vfio_find_ram_discard_listener(bcontainer, section);
+
+    g_assert(vrdl);
+    return vrdl->listener.notify_populate(&vrdl->listener, section) == 0;
 }
 
 int vfio_cpr_group_get_device_fd(int d, const char *name)

hw/vfio/listener.c

@@ -481,6 +481,13 @@ static void vfio_listener_region_add(MemoryListener *listener,
 {
     VFIOContainerBase *bcontainer = container_of(listener, VFIOContainerBase,
                                                  listener);
+    vfio_container_region_add(bcontainer, section, false);
+}
+
+void vfio_container_region_add(VFIOContainerBase *bcontainer,
+                               MemoryRegionSection *section,
+                               bool cpr_remap)
+{
     hwaddr iova, end;
     Int128 llend, llsize;
     void *vaddr;
@@ -516,6 +523,11 @@ static void vfio_listener_region_add(MemoryListener *listener,
         int iommu_idx;
 
         trace_vfio_listener_region_add_iommu(section->mr->name, iova, end);
+
+        if (cpr_remap) {
+            vfio_cpr_giommu_remap(bcontainer, section);
+        }
+
         /*
          * FIXME: For VFIO iommu types which have KVM acceleration to
          * avoid bouncing all map/unmaps through qemu this way, this
@@ -558,7 +570,12 @@ static void vfio_listener_region_add(MemoryListener *listener,
      * about changes.
      */
     if (memory_region_has_ram_discard_manager(section->mr)) {
-        vfio_ram_discard_register_listener(bcontainer, section);
+        if (!cpr_remap) {
+            vfio_ram_discard_register_listener(bcontainer, section);
+        } else if (!vfio_cpr_ram_discard_register_listener(bcontainer,
+                                                           section)) {
+            goto fail;
+        }
         return;
     }
 

include/hw/vfio/vfio-container-base.h

@@ -256,4 +256,7 @@ struct VFIOIOMMUClass {
 VFIORamDiscardListener *vfio_find_ram_discard_listener(
     VFIOContainerBase *bcontainer, MemoryRegionSection *section);
 
+void vfio_container_region_add(VFIOContainerBase *bcontainer,
+                               MemoryRegionSection *section, bool cpr_remap);
+
 #endif /* HW_VFIO_VFIO_CONTAINER_BASE_H */

include/hw/vfio/vfio-cpr.h

@@ -10,6 +10,7 @@
 #define HW_VFIO_VFIO_CPR_H
 
 #include "migration/misc.h"
+#include "system/memory.h"
 
 struct VFIOContainer;
 struct VFIOContainerBase;
@@ -17,6 +18,9 @@ struct VFIOGroup;
 
 typedef struct VFIOContainerCPR {
     Error *blocker;
+    bool vaddr_unmapped;
+    NotifierWithReturn transfer_notifier;
+    MemoryListener remap_listener;
     int (*saved_dma_map)(const struct VFIOContainerBase *bcontainer,
                          hwaddr iova, ram_addr_t size,
                          void *vaddr, bool readonly, MemoryRegion *mr);
@@ -42,4 +46,10 @@ int vfio_cpr_group_get_device_fd(int d, const char *name);
 bool vfio_cpr_container_match(struct VFIOContainer *container,
                               struct VFIOGroup *group, int fd);
 
+void vfio_cpr_giommu_remap(struct VFIOContainerBase *bcontainer,
+                           MemoryRegionSection *section);
+
+bool vfio_cpr_ram_discard_register_listener(
+    struct VFIOContainerBase *bcontainer, MemoryRegionSection *section);
+
 #endif /* HW_VFIO_VFIO_CPR_H */