Re: [PATCH] libxl: Remove qxl support for the 4.3 release

[Fabio Fantoni <fabio.fantoni@m2r.biz>]

Il 18/09/2013 10:07, Jan Beulich ha scritto:
>>>> On 16.09.13 at 16:10, Fabio Fantoni <fabio.fantoni@m2r.biz> wrote:
>> Il 05/07/2013 18:59, George Dunlap ha scritto:
>>> On Wed, May 29, 2013 at 11:25 PM, Andrew Cooper
>>> <andrew.cooper3@citrix.com> wrote:
>>>> On 29/05/2013 08:43, Ian Campbell wrote:
>>>>> On Tue, 2013-05-28 at 19:09 +0100, Keir Fraser wrote:
>>>>>> On 28/05/2013 17:51, "Ian Jackson" <Ian.Jackson@eu.citrix.com> wrote:
>>>>>>
>>>>>>> George Dunlap writes ("[PATCH] libxl: Remove qxl support for the 4.3
>>>>>>> release"):
>>>>>>>> The qxl drivers for Windows and Linux end up calling instructions
>>>>>>>> that cannot be used for MMIO at the moment.  Just for the 4.3 release,
>>>>>>>> remove qxl support.
>>>>>>>>
>>>>>>>> This patch should be reverted as soon as the 4.4 development window opens.
>>>>>>>>
>>>>>>>> The issue in question:
>>>>>>>>
>>>>>>>> (XEN) emulate.c:88:d18 bad mmio size 16
>>>>>>>> (XEN) io.c:201:d18 MMIO emulation failed @ 0033:7fd2de390430: f3 0f 6f
>>>>>>>> 19 41 83 e8 403
>>>>>>>>
>>>>>>>> The instruction in question is "movdqu (%rcx),%xmm3".  Xen knows how
>>>>>>>> to emulate it, but unfortunately %xmm3 is 16 bytes long, and the interface
>>>>>>>> between Xen and qemu at the moment would appear to only allow MMIO accesses
>>>>>>>> of 8 bytes.
>>>>>>>>
>>>>>>>> It's too late in the release cycle to find a fix or a workaround.
>>>>>>> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
>>>>>> It could be plumbed through hvmemul_do_io's multi-cycle read/write logic,
>>>>>> and done as two 8-byte cycles to qemu. This would avoid bloating the ioreq
>>>>>> structure that communicates to qemu.
>>>>> Are you proposing we do this for 4.3? I'm not sure how big that change
>>>>> would be in terms of impact (just that one instruction, any 16 byte
>>>>> operand?).
>>>>>
>>>>> Of course even if we did this for 4.3 we don't know what the next issue
>>>>> will be with QXL.
>>>>>
>>>>> Ian.
>>>> Furthermore, AVX instruction emulation would require support for 32byte
>>>> operands.  I don't see the multi-cycle logic scaling sensibly.
>>> Andrew, Keir, Jan, does any one of you fancy taking this on for 4.4?
>> Is there someone that can add full support for SSE on hvm domUs?
>> Thanks for any reply.
> Mind giving the attached patch a try?
>
> Jan
>

Thanks, I have tested your patch but qxl seems to have the same problem 
(qemu crash on domU xorg start).
I not see the MMIO error on logs, what must I do to see it or any 
similar debug information?
Tell me if I must do other specific test or you need other details.
Thanks for any reply.