Re: Xen 4.3 development update RC2 imminent

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

On 05/21/2013 03:31 PM, Andrew Cooper wrote:
> On 21/05/13 15:06, Anthony PERARD wrote:
>> On 20/05/13 11:33, George Dunlap wrote:
>>> * qxl not actually working
>>>    > qxl apparently not enabled during compile by default
>>>    > Appear to be some other bugs even when it is working:
>>>    >   http://lists.xen.org/archives/html/xen-devel/2012-11/msg00713.html
>>>    owner: ? (Anthony was going to take a look)
>>>    We need to either fix both of these problems or disable qxl for 4.3
>> I've been able to track down this error:
>>> Spice-CRITICAL **: red_memslots.c:123:get_virt: slot_id 194 too big,
>> addr=c2c2c2c2c2c2c2c2
>>
>> This little patch fix it:
>> diff --git a/hw/qxl.c b/hw/qxl.c
>> index 96887c4..db2e02e 100644
>> --- a/hw/qxl.c
>> +++ b/hw/qxl.c
>> @@ -390,6 +390,7 @@ static void init_qxl_ram(PCIQXLDevice *d)
>>       d->ram->int_pending = cpu_to_le32(0);
>>       d->ram->int_mask    = cpu_to_le32(0);
>>       d->ram->update_surface = 0;
>> +    d->ram->monitors_config = 0;
>>       SPICE_RING_INIT(&d->ram->cmd_ring);
>>       SPICE_RING_INIT(&d->ram->cursor_ring);
>>       SPICE_RING_INIT(&d->ram->release_ring);
>>
>> But then, once this applied, qxl is still not able to start. Xorg crash
>> (in the guest), and here is why:
>>
>> (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
>> (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
>
> Disassembly of section .data:
>
> 0000000000000000 <.data>:
>     0:    f3 0f 6f 19              movdqu (%rcx),%xmm3
>
> Xen does not support emulating SSE instructions.  We have sporadically
> seen similar errors from Windows guests.  The best guess I have managed
> to get so far is that %rcx is a pointer to something which Xen thinks is
> an MMIO page.
>
> In this case, it looks like X is copying from MMIO into an xmm register,
> scraping the framebuffer perhaps?  In the windows failure, it was the
> pagescrub trying to zero ram, which clearly indicated something wonky in
> the combined idea of the memory map.
>
> If Spice is doing something valid and sensible, then Xen will likely
> need extending to be able to emulate SSE instructions.
>
> Not that this helps much with the problem for 4.3

Hmm, is there any way to disable the SSE instructions in X and/or the 
qxl driver?

I'll take a quick look around to see what I can see...

  -George