Re: [Xen-devel] [PATCH] hvmloader: Intel GPU passthrough, reverse OpRegion

[Jean Guyader <jean.guyader@xxxxxxxxx>]

On 23 November 2011 17:28, Jean Guyader <jean.guyader@xxxxxxxxx> wrote:
> On 23 November 2011 17:20, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
>> On 23/11/2011 16:07, "Jean Guyader" <jean.guyader@xxxxxxxxxxxxx> wrote:
>>
>>>
>>> The Intel GPU uses a two pages NVS region called OpRegion.
>>> In order to get full support for the driver in the guest
>>> we need to map this region.
>>>
>>> This patch reserves 2 pages on the top of the RAM and
>>> mark this region as NVS in the e820. Then we write the
>>> address to the config space (offset 0xfc) so the device
>>> model can map the OpRegion at this address in the guest.
>>
>> Please use mem_hole_alloc() rather than adjusting {low,high}_mem_pgend.
>>
>
> Ok, that is handy.
>
>> Is it correct to do this for *all* gfx devices with Intel vendor id?
>>
>
> The OpRegion is a Intel GPU specific thing.
>

Sorry didn't read carefully the first time, yes I think it's correct
to do that for
all the Intel GPU. Maybe I can do a read on 0xfc first to check if I don't get
something dodgy like 0xfffffff or 0. I could also double check in Qemu that it's
a NVS region on the host, but that won't work for stub domain.

Jean

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