diff mbox series

[v3,5/6] vfio/migration: Block VFIO migration with postcopy migration

Message ID 20230906150853.22176-6-avihaih@nvidia.com
State New
Headers show
Series vfio/migration: Block VFIO migration with postcopy and background snapshot | expand

Commit Message

Avihai Horon Sept. 6, 2023, 3:08 p.m. UTC 
VFIO migration is not compatible with postcopy migration. A VFIO device
in the destination can't handle page faults for pages that have not been
sent yet.

Doing such migration will cause the VM to crash in the destination:

qemu-system-x86_64: VFIO_MAP_DMA failed: Bad address
qemu-system-x86_64: vfio_dma_map(0x55a28c7659d0, 0xc0000, 0xb000, 0x7f1b11a00000) = -14 (Bad address)
qemu: hardware error: vfio: DMA mapping failed, unable to continue

To prevent this, block VFIO migration with postcopy migration.

Reported-by: Yanghang Liu <yanghliu@redhat.com>
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Tested-by: Yanghang Liu <yanghliu@redhat.com>
---
 hw/vfio/migration.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

Comments

Peter Xu Sept. 6, 2023, 3:18 p.m. UTC | #1 
On Wed, Sep 06, 2023 at 06:08:52PM +0300, Avihai Horon wrote:
> VFIO migration is not compatible with postcopy migration. A VFIO device
> in the destination can't handle page faults for pages that have not been
> sent yet.
> 
> Doing such migration will cause the VM to crash in the destination:
> 
> qemu-system-x86_64: VFIO_MAP_DMA failed: Bad address
> qemu-system-x86_64: vfio_dma_map(0x55a28c7659d0, 0xc0000, 0xb000, 0x7f1b11a00000) = -14 (Bad address)
> qemu: hardware error: vfio: DMA mapping failed, unable to continue
> 
> To prevent this, block VFIO migration with postcopy migration.
> 
> Reported-by: Yanghang Liu <yanghliu@redhat.com>
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> Tested-by: Yanghang Liu <yanghliu@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 71855468fe..20994dc1d6 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -335,6 +335,27 @@  static bool vfio_precopy_supported(VFIODevice *vbasedev)
 
 /* ---------------------------------------------------------------------- */
 
+static int vfio_save_prepare(void *opaque, Error **errp)
+{
+    VFIODevice *vbasedev = opaque;
+
+    /*
+     * Snapshot doesn't use postcopy, so allow snapshot even if postcopy is on.
+     */
+    if (runstate_check(RUN_STATE_SAVE_VM)) {
+        return 0;
+    }
+
+    if (migrate_postcopy_ram()) {
+        error_setg(
+            errp, "%s: VFIO migration is not supported with postcopy migration",
+            vbasedev->name);
+        return -EOPNOTSUPP;
+    }
+
+    return 0;
+}
+
 static int vfio_save_setup(QEMUFile *f, void *opaque)
 {
     VFIODevice *vbasedev = opaque;
@@ -640,6 +661,7 @@  static bool vfio_switchover_ack_needed(void *opaque)
 }
 
 static const SaveVMHandlers savevm_vfio_handlers = {
+    .save_prepare = vfio_save_prepare,
     .save_setup = vfio_save_setup,
     .save_cleanup = vfio_save_cleanup,
     .state_pending_estimate = vfio_state_pending_estimate,