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

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

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.
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.