Re: [PATCH] spapr: Modify ibm, get-config-addr-info2 to set DEVNUM in PE config address.

["Oliver O'Halloran" <oohall@gmail.com>]

On Thu, Apr 29, 2021 at 7:02 PM Mahesh J Salgaonkar
<mahesh@linux.ibm.com> wrote:
>
> On 2021-04-28 22:33:45 Wed, Oliver O'Halloran wrote:
> > On Tue, Apr 27, 2021 at 9:56 PM Mahesh Salgaonkar <mahesh@linux.ibm.com> wrote:
> > >
> > > With upstream kernel, especially after commit 98ba956f6a389
> > > ("powerpc/pseries/eeh: Rework device EEH PE determination") we see that KVM
> > > guest isn't able to enable EEH option for PCI pass-through devices anymore.
> >
> > How are you passing the devices through to the guest?
>
> I am using libvirt with below xml section to add pass-through:
>
>     <hostdev mode='subsystem' type='pci' managed='yes'>
>       <driver name='vfio'/>
>       <source>
>         <address domain='0x0033' bus='0x01' slot='0x00' function='0x0'/>
>       </source>
>       <address type='pci' domain='0x0000' bus='0x01' slot='0x01' function='0x0' multifunction='on'/>
>     </hostdev>
>     <hostdev mode='subsystem' type='pci' managed='yes'>
>       <driver name='vfio'/>
>       <source>
>         <address domain='0x0033' bus='0x01' slot='0x00' function='0x1'/>
>       </source>
>       <address type='pci' domain='0x0000' bus='0x01' slot='0x01' function='0x1' multifunction='on'/>
>     </hostdev>
>
> Looks like libvirt does not allow pass through device in slot zero, and
> throws following error.
>
> error: XML error: Invalid PCI address 0000:01:00.0. slot must be >= 1
> Failed. Try again? [y,n,i,f,?]:

That's pretty odd and I have no idea why that's happening. I seem to
remember being able to use slot 0 for vfio devices when doing the
passthru manually with the qemu command line so this might be a
libvirt quirk.

> *snip*
>
> Agree. I realize my fix is not correctly handling this. The current code
> under ibm,set-eeh-option is checking for individual PCI device presence.
> Better fix should be to check if there is any PCI device (vfio-pci)
> present under specified bus and enable the EEH if found. And no change
> in return value of get-config-addr-info2. What do you say ?

That sounds reasonable. You would however need to verify that all the
devices on that bus are within the same PE on the hypervisor side.