Re: [Xen-devel] [PATCH v5 02/11] vpci: introduce basic handlers to trap accesses to the PCI config space

[Julien Grall <julien.grall@xxxxxxx>]

On 12/09/17 11:58, Roger Pau Monné wrote:
> On Tue, Sep 12, 2017 at 11:42:38AM +0100, Julien Grall wrote:
> > Hi Roger,
> >
> > On 14/08/17 15:28, Roger Pau Monne wrote:
> > > This functionality is going to reside in vpci.c (and the corresponding
> > > vpci.h header), and should be arch-agnostic. The handlers introduced
> > > in this patch setup the basic functionality required in order to trap
> > > accesses to the PCI config space, and allow decoding the address and
> > > finding the corresponding handler that should handle the access
> > > (although no handlers are implemented).
> > If I understand correctly this patch, the virtual BDF will always correspond
> > to the physical BDF. Is that right? If so, would you mind to explain why
> > such restriction?
> Yes, this is not a limitation of this patch, but of the implementation
> that follows. Likely this will be expanded when support for DomU is
> added, but for Dom0 at least on x86 adding such a translation layer is
> not needed, since I see no reason to present a different PCI topology
> to Dom0.
I think this will be the same for ARM. Dom0 will always have pBDF == 
vBDF. For guest will likely want pBDF != vBDF.
This answer to my other question regarding the plan to support vBDF != 
pBDF :). Thanks.
> Thanks, Roger.
--
Julien Grall

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