Re: GPU passthrough issue when VM is configured with 4G memory

[George Dunlap <george.dunlap@eu.citrix.com>]

On 15/04/13 22:22, Pasi Kärkkäinen wrote:
> On Tue, Mar 26, 2013 at 09:37:53AM +0000, Hanweidong wrote:
>>>> HVM_BELOW_4G_RAM_END is f0000000. If we change HVM_BELOW_4G_RAM_END
>>> to e0000000,
>>>> Which it's consistent with hvmloader when assigning a GPU, and then
>>> guest worked
>>>> for us. So we wondering that xen_ram_init in QEMU should be
>>> consistent with
>>>> hvmloader.
>>>>
>>>> In addition, we found QEMU uses hardcode 0xe0000000 in pc_init1() as
>>> below.
>>>> Should keep these places handle the consistent mmio hole or not?
>>>>
>>>>      if (ram_size >= 0xe0000000 ) {
>>>>          above_4g_mem_size = ram_size - 0xe0000000;
>>>>          below_4g_mem_size = 0xe0000000;
>>>>      } else {
>>>>          above_4g_mem_size = 0;
>>>>          below_4g_mem_size = ram_size;
>>>>      }
>>> The guys at Intel sent a couple of patches recently to fix this issue:
>>>
>>> http://marc.info/?l=xen-devel&m=136150317011027
>>> http://marc.info/?l=qemu-devel&m=136177475215360&w=2
>>>
>>> Do they solve your problem?
>> These two patches didn't solve our problem.
>>
> Any updates on this? It'd be nice to get this fixed before Xen 4.3.

It looks like the qemu guys didn't like the patch; they said there was 
already an interface to get this information.  I didn't see whether Xu 
Dong followed that up or not.

I'm going to list this as a bug, hopefully we can get it sorted out.

  -George


>
> Thanks,
>
> -- Pasi
>   
>> --weidong
>>
>>> Xudong and Xiantao,
>>> are you going to send an update of the second patch to QEMU?