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Re: [PATCH 2/2] failover: don't allow to migrate a paused VM that needs
Re: [PATCH 2/2] failover: don't allow to migrate a paused VM that needs PCI unplug
Tue, 2 Nov 2021 18:43:11 +0100
Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0
On 02/11/2021 18:08, Michael S. Tsirkin wrote:
On Tue, Nov 02, 2021 at 06:06:51PM +0100, Laurent Vivier wrote:
On 02/11/2021 16:04, Michael S. Tsirkin wrote:
On Wed, Sep 29, 2021 at 04:43:11PM +0200, Laurent Vivier wrote:
As the guest OS is paused, we will never receive the unplug event
from the kernel and the migration cannot continue.
Signed-off-by: Laurent Vivier <email@example.com>
Well ... what if user previously did
we are breaking it now for no good reason.
Further, how about
are we going to break this too? by failing pause?
TL;DR: This patch only prevents to migrate a VFIO device as failover allows
to start a migration with a VFIO device plugged in.
* before this patch:
- pause and start migration and unpause-> fails if we unpause too late
because we migrate a VFIO device, works otherwise
confused about this one. can you explain pls?
Sorry, I've been confused by another bug: with ACPI unplug, we don't wait the unplug, and
so if the machine is paused the VFIO is "migrated" and we have an error message on the
destination side as the card cannot be plugged back.
but with PCIe native hotplug ("-global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off")
before this patch:
if we pause and then start the migration, migration hangs until we unpause the VM. But the
migration can hangs forever if the VM is never unpaused. Normally migration of a paused VM
should not hang.
after this patch:
if we pause and then start the migration, the migration fails because of the
Remember that the migration of a VM with a VFIO device normally fails, so a user should
not try to migrate a VM with a VFIO device except if he knows he is using failover, and in
this case he should know he must not pause the VM.