Re: Xen 4.3 development update RC2 imminent

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

On 23/05/13 11:39, Andrew Cooper wrote:
> On 23/05/13 11:36, Fabio Fantoni wrote:
>> Il 23/05/2013 09:39, Jan Beulich ha scritto:
>>>>>> On 22.05.13 at 18:54, George Dunlap <george.dunlap@eu.citrix.com> wrote:
>>>> On 22/05/13 17:30, Pasi Kärkkäinen wrote:
>>>>> On Wed, May 22, 2013 at 04:05:27PM +0100, George Dunlap wrote:
>>>>> Hmm, for testing, can we use cpuid to mask out SSE,
>>>>> and then try qxl ?
>>>> That had occurred to me -- Andrew / Jan, do you know which flag might
>>>> disable this particular instruction?
>>>>
>>>> I guess we could try just disabling all the SSE instructions.
>>> movdqu is an SSE2 instruction, so disabling bit 26 of CPUID EDX
>>> output to EAX=1 input.
>> Can you explain better please?
>> Should I add this to test it?
>> cpuid="host,sse=0,sse2=0,ssse3=0,sse4_1=0,sse4_2=0,eax=1"
> It will likely not work.  SSE2 is an architectural requirement for 64bit.
>
> It means that 64bit code may assume the presence of SSE2.  Xen amongst
> other software does make this assumption.

It might work if he's using 32-bit.

Fabio, as I said in my initial e-mail, you need to:

1. Run "cat /proc/cpuinfo" on your dom0
2. Look at the line that says "features:"
3. Find all the things that contain "sse" > 2 (sse2, ssse3, &c)
4. Set them to 0 in the "cpuid" field like above.

Every processor will be a bit different -- you can't just copy mine and 
expect it to work.

Don't include "eax=1" -- Jan is thinking of a different interface.

  -George

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