Re: [Qemu-devel] [PATCH] pci: fix requester id with PCI bridges

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, May 12, 2016 at 03:32:03PM +0800, Peter Xu wrote:
> On Thu, May 12, 2016 at 10:11:31AM +0300, Michael S. Tsirkin wrote:
> > On Wed, May 11, 2016 at 02:53:18PM +0800, Peter Xu wrote:
> > > On Wed, May 11, 2016 at 02:40:30PM +0800, Peter Xu wrote:
> > > > Recently I encountered issue when debugging Intel IOMMU IR codes,
> > > > that interrupts are not working correctly with PCI bridges (reported
> > > > by Radim). This patch fixes the problem. I assume requester ID
> > > > should be the devfn on root PCI bus (that's how I understand it
> > > > before, and also in guest kernel, IRTE entry SID is filled in that
> > > > way), however I failed to find any good document to confirm
> > > > this. Please let me know if this is correct (or I made any
> > > > mistake).
> > > 
> > > One thing to mention is that, this patch does *not* fix the problem
> > > if directly applied, because IR patchset introduced another patch
> > > that also need a similar fix. In case if there is someone (Radim?)
> > > who would like to try this patch, we need to apply this patch as
> > > well:
> > > 
> > > ---8<---
> > > 
> > > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > > index 80b3251..0876a1c 100644
> > > --- a/target-i386/kvm.c
> > > +++ b/target-i386/kvm.c
> > > @@ -3342,7 +3342,8 @@ int kvm_arch_fixup_msi_route(struct kvm_irq_routing_entry *route,
> > >          src.data = route->u.msi.data;
> > > 
> > >          ret = class->int_remap(iommu, &src, &dst, dev ? \
> > > -                               pci_requester_id(dev) : X86_IOMMU_SID_INVALID);
> > > +                               pci_requester_id_recursive(dev) : \
> > > +                               X86_IOMMU_SID_INVALID);
> > >          if (ret) {
> > >              trace_kvm_x86_fixup_msi_error(route->gsi);
> > >              return 1;
> > > 
> > > --->8---
> > > 
> > > This should be able to be applied directly onto IR v6 patchset as
> > > well.
> > > 
> > > Thanks,
> > > 
> > > -- peterx
> > 
> > I really dislike the name pci_requester_id_recursive.
> 
> Do you have better suggestion on this? :)
> 
> > Are there cases where we need the original requester id value?
> > I am guessing not, and if I'm right we should just change the implementation
> > of pci_requester_id to DTRT.
> 
> There are two other callers for it (besides the MSI one):
> 
> - assigned_device_pci_cap_init()
> - do_pcie_aer_inject_error()
> 
> For both the cases, I am not sure whether we can do the replacement.
> 
> -- peterx

Read the specs please. We can't just pile on APIs.

-- 
MST