Re: [Xen-devel] FIXME question

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Monday, June 27, 2016 5:51 PM
> To: Jan Beulich <JBeulich@xxxxxxxx>; Xu, Quan <quan.xu@xxxxxxxxx>
> Cc: Tian, Kevin <kevin.tian@xxxxxxxxx>; Wu, Feng <feng.wu@xxxxxxxxx>; xen-
> devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] FIXME question
> 
> On 27/06/16 10:32, Jan Beulich wrote:
> >>>> On 27.06.16 at 11:23, <quan.xu@xxxxxxxxx> wrote:
> >> Hi,
> >>
> >> When I read IOMMU code,
> >> In xen/drivers/passthrough/vtd/intremap.c : pi_update_irte()..
> >> There are a FIXME --
> >> ''
> >> * FIXME: For performance reasons we should store the 'iommu' pointer in
> >> * 'struct msi_desc' in some other place, so we don't need to waste
> >> * time searching it here.
> >> "
> >>
> >> IMO, we are better to store the 'iommu' pointer in pci_dev, then
> >> could I fix it as:
> > Sounds reasonable.
> 
> I agree.
> 
> >
> > Jan
> >
> >> 1. save a void *iommu  in pci_dev structure:
> >>
> >> --- a/xen/include/xen/pci.h
> >> +++ b/xen/include/xen/pci.h
> >> @@ -83,6 +83,8 @@ struct pci_dev {
> >>  #define PT_FAULT_THRESHOLD 10
> >>      } fault;
> >>      u64 vf_rlen[6];
> >> +
> >> +   void *iommu; /* No common IOMMU struct so use void pointer */
> 
> Longer term, it would be nice to have concrete IOMMU type with
> implementation specific fields hidden in a union, but void * will work
> for now.

Agree, I think something like below should be the case:

struct arch_pci_dev {
     vmask_t used_vectors;
+    union {
+        struct acpi_drhd_unit *drhd;
+        /* AMD can add its counterpart here if needed */
+    };
 };

Thanks,
Feng

> 
> ~Andrew
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