Xen devel - May 2012 - [PATCH][RESEND] qemu-xen: Intel GPU passthrough, fix OpRegion mapping (v3)

The OpRegion shouldn''t be mapped 1:1 because the address in the host
can''t be used in the guest directly.

This patch traps read and write access to the opregion of the Intel
GPU config space (offset 0xfc).

To work correctly this patch needs a change in hvmloader.

HVMloader will allocate 2 pages for the OpRegion and write this address
on the config space of the Intel GPU. Qemu will trap and map the host
OpRegion to the guest. Any write to this offset after that won''t have
any effect. Any read of this config space offset will return the address
in the guest.

Signed-off-by: Jean Guyader <jean.guyader@eu.citrix.com>


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On 10 May 2012 20:07, Jean Guyader <jean.guyader@gmail.com>
wrote:
> The OpRegion shouldn''t be mapped 1:1 because the address in the
host
> can''t be used in the guest directly.
>
> This patch traps read and write access to the opregion of the Intel
> GPU config space (offset 0x).
>
> To work correctly this patch needs a change in hvmloader.
>
> HVMloader will allocate 2 pages for the OpRegion and write this address
> on the config space of the Intel GPU. Qemu will trap and map the host
> OpRegion to the guest. Any write to this offset after that won''t
have
> any effect. Any read of this config space offset will return the address
> in the guest.
>
> Signed-off-by: Jean Guyader <jean.guyader@eu.citrix.com>
Sorry forgot to say, it was acked by Stefano.

Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

Jean Guyader writes ("Re: [Xen-devel] [PATCH][RESEND] qemu-xen: Intel GPU
passthrough, fix OpRegion mapping (v3)"):
> On 10 May 2012 20:07, Jean Guyader <jean.guyader@gmail.com> wrote:
> > The OpRegion shouldn''t be mapped 1:1 because the address in
the host
> > can''t be used in the guest directly.
> 
> Sorry forgot to say, it was acked by Stefano.
> 
> Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Thanks.

Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>