Re: [Qemu-devel] SR-IOV PF reset and QEMU VFs VFIO passthrough

[Benoît Canet]

Thanks a lot for the answer.

Best regards

Benoît

> Le Sunday 02 Jun 2013 à 08:11:42 (-0600), Alex Williamson a écrit :
> On Sat, 2013-06-01 at 14:13 +0200, Benoît Canet wrote:
> > Hello,
> > 
> > I may have soon the PF driver of an SR-IOV card to code and make work with
> > QEMU/KVM so I have the following questions.
> > 
> > In an AMD64 setup where QEMU use VFIO to passthrough the VFs of an SR-IOV 
> > card
> > to a guest will the consequences of a PF FLR be handled fine by QEMU and the
> > guest ?
> > 
> > I read that pci_reset_function would call pci_restore_state restoring the 
> > SR-IOV
> > configuration after the reset of the PF.
> > 
> > The ways the hardware work means that the VFs would disappear and reappear 
> > in a
> > short lapse of time.
> > 
> > Will these events be handled by the kernel pci hotplug code ?
> > 
> > Given that the PF driver restore the PF config space after the reset will 
> > /sys
> > files used by QEMU disappear and reappear messing the QEMU VFIO passthrough 
> > or
> > will it goes smoothly ?
> 
> On an Intel 82576 SR-IOV NIC, a FLR of the PF does not cause the VFs to
> be removed.  It's not clear to me that they continue working across the
> reset, but there is no hotplug.  If there was a hotplug, vfio-pci won't
> release the device while it's in use, so the hotplug would be blocked
> until the devices becomes unused, such as from the VM being shutdown.
> Thanks,
> 
> Alex
> 
>