Re: [Xen-devel] [PATCH v7] VT-d: use correct BDF for VF to search VT-d unit

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Aug 23, 2017 at 09:05:14AM +0800, Chao Gao wrote:
> On Tue, Aug 22, 2017 at 06:43:49AM -0600, Jan Beulich wrote:
> >>>> On 21.08.17 at 23:52, <chao.gao@xxxxxxxxx> wrote:
> >> --- a/xen/include/xen/pci.h
> >> +++ b/xen/include/xen/pci.h
> >> @@ -39,6 +39,10 @@
> >>  #define PCI_SBDF3(s,b,df) ((((s) & 0xffff) << 16) | PCI_BDF2(b, df))
> >>  
> >>  struct pci_dev_info {
> >> +    /*
> >> +     * When 'is_virtfn' is set, 'is_extfn' is re-used to indicate whether
> >> +     * the PF of this VF is an extended function.
> >> +     */
> >
> >I'd be inclined to extend the comment by appending ", as a VF itself
> >can never be an extended function." Is that correct? If so, would
> 
> Hi, Jan and Roger.
> 
> Strictly speaking, the VF can be an extended function. The definition is
> within ARI device (in this kind of device, device field is treated as an
> extension of function number) and function number is greater than 7. But
> this field isn't used as we don't care about whether a VF is or not an
> extended function (at least at present).
> 
> Eric reviewed this patch and told me we may match
> 'if ( pdev->info.is_extfn )' in acpi_find_matched_drhd_unit.
> So we may introduce a new field like what I do in v6 or check
> 'pdev->info.is_virtfn' first in acpi_find_matched_drhd_unit (maybe other
> places we check pdev->info.is_extfn).
> 
> Which one do you prefer?

Looking at this again I'm not sure why you need any modifications to
acpi_find_matched_drhd_unit. If the virtual function is an extended
function pdev->bus should be equal to pdev->info.physfn.bus, in which
case the already existing is_extfn check will already DTRT?

Ie: an extended VF should always have the same bus as the PF it
belongs to, unless I'm missing something.

Roger.

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