Re: [Xen-devel] sse, mmx support for hvm guests

To:	"Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] sse, mmx support for hvm guests
From:	"Ashish Bijlani" <ashish.bijlani@xxxxxxxxx>
Date:	Sat, 25 Oct 2008 19:30:12 -0400
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date:	Sat, 25 Oct 2008 16:30:34 -0700
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it's just masking the sse/mmx features from cpuid return value or
something more to it? because i tried masking sse/mmx features from
cpuid and now the hvm domain doesn't boot!! any idea if sse/mmx
support can be disabled using bios?

Thanks,
Ashish

On Sat, Oct 25, 2008 at 7:13 PM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
> On 25/10/08 20:34, "Ashish Bijlani" <ashish.bijlani@xxxxxxxxx> wrote:
>
>> I've a quad-core x86_64 machine (Intel Xeon), with sse/mmx support.
>> However, I want to disable sse/mmx support from HVM guests. How can I
>> do this? Also, is it reasonable to expect illegal instruction fault in
>> non-root VMX mode if a guest VM runs an application with sse/mmx
>> instructions?
>
> You can hide SSE/MMX in CPUID info, so the guest should not attempt to use
> the instructions. This is obviously true since CPUID causes vmexit and then
> the instruction is always emulated. But I don't think you can make the
> sse/mmx instructions fault if the guest does actually try to use them
> anyway.
>
>  -- Keir
>
>
>

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Re: [Xen-devel] sse, mmx support for hvm guests