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qemu-kvm/SOURCES/kvm-vfio-migration-Block-VF...

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From df7814de08c8c7c45eacb7b9d9ead9be4d1e3baf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@redhat.com>
Date: Mon, 11 Sep 2023 16:10:19 +0200
Subject: [PATCH 4/4] vfio/migration: Block VFIO migration with postcopy
migration
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Cédric Le Goater <clg@redhat.com>
RH-MergeRequest: 318: VFIO migration: fix a QEMU crash when postcopy is enabled
RH-Bugzilla: 2229868
RH-Acked-by: Alex Williamson <None>
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Commit: [4/4] 36eedf879547044c2ba2763fb48784a95f9e4ea7
Bugzilla: https://bugzilla.redhat.com/2229868
commit bf7ef7a2da3e61dc104f26c679c9465e3fbe7dde
Author: Avihai Horon <avihaih@nvidia.com>
Date: Wed Sep 6 18:08:52 2023 +0300
vfio/migration: Block VFIO migration with postcopy migration
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>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
hw/vfio/migration.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 2674f4bc47..4f018c7531 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -331,6 +331,27 @@ 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;
@@ -630,6 +651,7 @@ 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,
--
2.39.3