Re: [Qemu-devel] [PATCH for 2.1] vfio: use correct runstate

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 2014-06-27 at 13:51 -0400, Paolo Bonzini wrote:
> ----- Messaggio originale -----
> > Da: "Alex Williamson" <alex.williamson@redhat.com>
> > A: "Paolo Bonzini" <pbonzini@redhat.com>
> > Cc: qemu-devel@nongnu.org, qemu-trivial@nongnu.org
> > Inviato: Venerdì, 27 giugno 2014 18:34:59
> > Oggetto: Re: [PATCH for 2.1] vfio: use correct runstate
> > 
> > On Fri, 2014-06-27 at 16:32 +0200, Paolo Bonzini wrote:
> > > io-error is for block device errors; it should always be preceded
> > > by a BLOCK_IO_ERROR event.
> > 
> > Where does this requirement come from?  I only see a loose association
> > of IO_ERROR to disk in libvirt and none in QEMU.
> 
> See the RunState enum in qapi-schema.json:
> 
> ##
> # @RunState
> #
> # An enumeration of VM run states.
> #
> # ...
> #
> # @internal-error: An internal error that prevents further guest execution
> # has occurred
> #
> # @io-error: the last IOP has failed and the device is configured to pause
> # on I/O errors
> #
> # @paused: guest has been paused via the 'stop' command
> 
> The point of io-error is that management can look at block devices, see if
> any have an error reported, and then resume execution (see documentation of
> rerror=stop and werror=stop/enospc).  This is counter to the intentions you
> have in vfio.
> 
> > > I think vfio wants to use
> > > RUN_STATE_INTERNAL_ERROR instead.
> > 
> > But that seems to put us into an "unknown" paused state in libvirt.
> 
> I think paused is incorrect, because (unlike RUN_STATE_IO_ERROR), you cannot
> resume from RUN_STATE_INTERNAL_ERROR except with a reset.  QEMU enforces that,
> and this matches the error you are reporting:
> 
>     error_report("%s(%04x:%02x:%02x.%x) Unrecoverable error detected.  "
>                  "Please collect any data possible and then kill the guest",
>                  __func__, vdev->host.domain, vdev->host.bus,
>                  vdev->host.slot, vdev->host.function);
> 
> libvirt has a crashed state, I think that's what libvirt should call the
> internal-error runstate.  IIRC on Xen you get to crashed when the processor
> raises an error on vmentry, for example.
> 
> Libvirt only knows about crashed/unknown, but one could add crashed/internal-error
> too.

Ok, I'll go with it.  I'll include this in the pull request I intend to
do on Monday.  Thanks,

Alex