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

[Keir Fraser <keir@xen.org>]

On 24/11/2011 09:35, "Jean Guyader" <jean.guyader@eu.citrix.com> wrote:

> On 23/11 05:20, Keir Fraser wrote:
>> On 23/11/2011 16:07, "Jean Guyader" <jean.guyader@eu.citrix.com> 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.
>> 
> 
> I'm calling mem_hole_alloc() in pci_setup (see patch attached),
> but that causes an overlap in e820, is that expected?

You'll have to adjust your changes to build_e820_table() to split the range
RESERVED_MEMBASE-0x10000000 into two pieces partitioned by your NVS region.

The region starting at RESERVED_MEMBASE comes *before* your NVS region. Then
you add an another reserved region up to 0x1000000 if your NVS region
exists.

 -- Keir

> (XEN) HVM5: E820 table:
> (XEN) HVM5:  [00]: 00000000:00000000 - 00000000:0009e000: RAM
> (XEN) HVM5:  [01]: 00000000:0009e000 - 00000000:000a0000: RESERVED
> (XEN) HVM5:  HOLE: 00000000:000a0000 - 00000000:000e0000
> (XEN) HVM5:  [02]: 00000000:000e0000 - 00000000:00100000: RESERVED
> (XEN) HVM5:  [03]: 00000000:00100000 - 00000000:3f800000: RAM
> (XEN) HVM5:  HOLE: 00000000:3f800000 - 00000000:feff8000
> (XEN) HVM5:  [04]: 00000000:feff8000 - 00000000:feffa000: NVS
> (XEN) HVM5:  OVERLAP!!
> (XEN) HVM5:  [05]: 00000000:fc000000 - 00000001:00000000: RESERVED
> 
> Jean