On 01/09/2023 18:51, Peter Xu wrote:
External email: Use caution opening links or attachments On Thu, Aug 31, 2023 at 03:57:01PM +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 <yangh...@redhat.com> Signed-off-by: Avihai Horon <avih...@nvidia.com> --- hw/vfio/migration.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) 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; + }Just purely curious: will it really work to save a snapshot for the GPU assigned use case?
I have never tried that. Adding Tarun, maybe he can answer that. Thanks.
+ + if (migrate_postcopy_ram()) { + error_setg( + errp, "%s: VFIO migration is not supported with postcopy migration", + vbasedev->name); + return -EOPNOTSUPP; + } + + return 0; +}-- Peter Xu
