Re: [Xen-devel] PCI Pass-through in Xen ARM: Draft 4

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 14 Aug 2015, Jan Beulich wrote:
> >>> On 14.08.15 at 16:03, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Fri, 14 Aug 2015, Jan Beulich wrote:
> >> >>> On 14.08.15 at 15:21, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >> > On Fri, 14 Aug 2015, Jan Beulich wrote:
> >> >> it's even less clear how you'd expect to suppress this in other guest
> >> >> OSes (Windows - afaik - being able to run on ARM certainly makes it
> >> >> a candidate guest, even if maybe this doesn't work today), namely
> >> >> such not having any pcifront. And I hope this design discussion isn't
> >> >> limiting itself to Linux guests.
> >> > 
> >> > We'll write down in the ABI documentation that BARs reassignments are
> >> > not supported.
> >> 
> >> I.e. guests doing so Will Not Work (TM), with users (usually not reading
> >> ABI docs) learning it the hard way. Not nice, but a way to handle it.
> > 
> > The target of the ABI docs is not users, but kernel developers, who
> > should most definitely read them and fix their kernels.
> 
> ??? (We're talking of unmodified, closed source OSes here.)

If you are thinking of Windows for ARM64, there isn't one yet.  When/if
it will become available, there are going to be a number of issues to
address before we can run it as a guest on Xen on ARM with the current
architecture which doesn't do emulation. I am hopeful that we'll be able
to have a discussion on ABI issues such as this one.

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