From mboxrd@z Thu Jan  1 00:00:00 1970
From: Don Dutile <ddutile@redhat.com>
Subject: Re: [Qemu-devel] SR-IOV PF reset and QEMU VFs VFIO passthrough
Date: Mon, 03 Jun 2013 14:41:04 -0400
Message-ID: <51ACE340.1030406@redhat.com>
References: <20130601121320.GC5157@irqsave.net>
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To: =?ISO-8859-1?Q?Beno=EEt_Canet?= <benoit.canet@irqsave.net>
Cc: linux-pci@vger.kernel.org, qemu-devel@nongnu.org, iommu@lists.linux-foundation.org, alex.williamson@redhat.com
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On 06/01/2013 08:13 AM, Beno=EEt 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 ?
>
the reset occurs long before the device is passed to the guest.

> I read that pci_reset_function would call pci_restore_state restoring=
 the SR-IOV
> configuration after the reset of the PF.
>
correct.

> The ways the hardware work means that the VFs would disappear and rea=
ppear in a
> short lapse of time.
>
Not sure your definitiion of 'disappear'.  If you mean: if I had anothe=
r thread
poking at the device, the device would appear to be removed, then come =
back (if os
poking hasn't crashed from the device's lack of response).
If you mean the VF gets entirely removed from the PCI tree, then no.
A pci reset !=3D hot unplug/plug.  The device remains in the device tre=
e.

> Will these events be handled by the kernel pci hotplug code ?
>
'these events' ??? -- which events....
=46LR is currently done by libvirt & qemu/vfio to ensure assigned devic=
es are quiesced
as they are switched from host->guest domain, and guest->(back-to-)host=
 domain.

> Given that the PF driver restore the PF config space after the reset =
will /sys
The PF driver doesn't do the config space restore -- it's done in PCI c=
ore code.

> files used by QEMU disappear and reappear messing the QEMU VFIO passt=
hrough or
As stated above, the devices don't disappear from the device tree, so t=
hey don't
get removed/added to the /sys(/bus/pci/...) files.

> will it goes smoothly ?
>
it goes smoothly today.... :-/

> Best regards
>
> Beno=EEt Canet
>