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

[Don Dutile]

On 06/03/2013 05:27 PM, Benoît Canet wrote:
> > > I was asking this because the PF driver should reset the PF while the VF are
> > > used by VFIO/QEMU when the PF doesn't respond anymore.
> > What your VF does while your PF is being reset is PF (&  VF) dependent.
> > A 'good design' would not impact the VF operation, other than to stall it until
> > the PF completed reset.  My experience, though, is that the PF has to be brought
> > up to some level of functionality to share the physical resources with the VFs.
>
> When the PF does an FLR the hardware go back to its default state, the SR-IOV
> configuration is gone and the VFs disappears from the bus.
> Then the restore state function of the kernel reset code would bring the SR-IOV
> PF configuration back.
Ok, now you're a bit mis-led here.
The configuration header for SRIOV is _not_ put back.
Only the std, PCI config header section is put back in place, along with
msi(x), pm-caps.
If the hw wipes out all VF state setup (which it should, IMO), all VF 
configuration
will be lost in the hw...
*but*, the PCI core will still think the VFs exist (not hot-unplugged, no more 
than PF was);
trying to setup the VFs again, will fail (or worse).

> The hardware also have a privately owned SR-IOV related configuration in the PF
> configuration space. This configuration is used to configure the VFs resources.
> (memory)
Per the SRIOV spec, yes, but that's in PCIe ext cfg space.
That area of the PCI configuration is not saved or restored by dev-reset.

> Best regards
>
> Benoît Canet
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