Re: [Xen-devel] Xen 4.3 development update RC2 imminent

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.05.13 at 18:54, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
> On 22/05/13 17:30, Pasi KÃrkkÃinen 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.

However, just like the hypervisor itself does, 64-bit code may
imply SSE2 to be available unconditionally (i.e. without looking at
any feature flags). In particular, both single and double precision
math are done via SSE/SSE2 instructions rather than FPU ones by
default on x86-64.

Jan

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