netdev - Re: [PATCH v13 vfio 6/7] vfio/pds: Add support for firmware recovery

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Date: Fri, 4 Aug 2023 15:03:31 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Brett Creeley <bcreeley@....com>
Cc: Brett Creeley <brett.creeley@....com>, kvm@...r.kernel.org,
	netdev@...r.kernel.org, alex.williamson@...hat.com,
	yishaih@...dia.com, shameerali.kolothum.thodi@...wei.com,
	kevin.tian@...el.com, simon.horman@...igine.com,
	shannon.nelson@....com
Subject: Re: [PATCH v13 vfio 6/7] vfio/pds: Add support for firmware recovery

On Fri, Aug 04, 2023 at 10:34:18AM -0700, Brett Creeley wrote:
> 
> 
> On 8/4/2023 10:18 AM, Jason Gunthorpe wrote:
> > Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> > 
> > 
> > On Tue, Jul 25, 2023 at 02:40:24PM -0700, Brett Creeley wrote:
> > > It's possible that the device firmware crashes and is able to recover
> > > due to some configuration and/or other issue. If a live migration
> > > is in progress while the firmware crashes, the live migration will
> > > fail. However, the VF PCI device should still be functional post
> > > crash recovery and subsequent migrations should go through as
> > > expected.
> > > 
> > > When the pds_core device notices that firmware crashes it sends an
> > > event to all its client drivers. When the pds_vfio driver receives
> > > this event while migration is in progress it will request a deferred
> > > reset on the next migration state transition. This state transition
> > > will report failure as well as any subsequent state transition
> > > requests from the VMM/VFIO. Based on uapi/vfio.h the only way out of
> > > VFIO_DEVICE_STATE_ERROR is by issuing VFIO_DEVICE_RESET. Once this
> > > reset is done, the migration state will be reset to
> > > VFIO_DEVICE_STATE_RUNNING and migration can be performed.
> > 
> > Have you actually tested this? Does the qemu side respond properly if
> > this happens during a migration?
> > 
> > Jason
> 
> Yes, this has actually been tested. It's not necessary clean as far as the
> log messages go because the driver may still be getting requests (i.e. dirty
> log requests), but the noise should be okay because this is a very rare
> event.
> 
> QEMU does respond properly and in the manner I mentioned above.

But what actually happens?

QEMU aborts the migration and FLRs the device and then the VM has a
totally trashed PCI function?

Can the VM recover from this?

Jason