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

To: Ashish Bijlani <ashish.bijlani@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] sse, mmx support for hvm guests
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Sun, 26 Oct 2008 00:13:32 +0100
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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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