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

[Mahesh J Salgaonkar]

On 2021-04-30 07:52:58 Fri, Daniel Henrique Barboza wrote:
> 
> 
> On 4/29/21 6:02 AM, Mahesh J Salgaonkar 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.
> 
> There's no such restriction in Libvirt, at least as far as I remember.
> 
> > 
> > error: XML error: Invalid PCI address 0000:01:00.0. slot must be >= 1
> > Failed. Try again? [y,n,i,f,?]:
> 
> 
> This looks odd. The error message is complaining about 0000:01:00.0 but
> your XML up there is declaring 0000:01:01.0.

Above XML snipphet is working one. I see the XML error when I change slot
value to zero.

> 
> Also, the 'multifunction' bool is usually used only in the function 0
> passthrough, indicating that the guest will configure all other functions as
> the the multifunction device. You can ignore this bool in the XML for
> PCI passthrough if you don't care about the guest seeing this device as
> multifunction (i.e. all functions in the same IOMMU group and so on).
> 

Thanks,
-Mahesh.