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Re: [Xen-devel] [Patch] Adding back CPUID support for Xsave

To: Keir Fraser <keir@xxxxxxx>
Subject: Re: [Xen-devel] [Patch] Adding back CPUID support for Xsave
From: Haitao Shan <maillists.shan@xxxxxxxxx>
Date: Tue, 9 Nov 2010 17:02:17 +0800
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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I remember cpuid exposure is covered by hvm_cpuid(), which is done by
former (long ago) patches.
Probably we may clean that a bit? So that both PV and HVM have the
same mechanism.

I have considered AVX exposure. My concern is: if AVX is considered to
be relying on XSAVE(of course, it is the truth), will we need to add
future features one by one since they are likely all dependent on
Or could we just let it be, since even they see it, they can not use it, anyway.

Shan Haitao

2010/11/9 Keir Fraser <keir@xxxxxxx>:
> Thanks, this looks better. I have some further questions however.
> You appear to only be exposing XSAVE to PV guests -- Why is that?
> Also, the patch passes the AVX feature unconditionally through to HVM guests
> -- firstly, why only visible HVM guests; and secondly, should it not be
> conditional on XSAVE support in the hypervisor (don't we need XSAVE to be
> able to save/restore AVX state)?
>  -- Keir
> On 09/11/2010 02:31, "Haitao Shan" <maillists.shan@xxxxxxxxx> wrote:
>> Hi, Keir,
>> This patch adds back the reverted CPUID support for XSAVE feature. Can
>> you have a review?
>> Signed-off-by: Shan Haitao <haitao.shan@xxxxxxxxx>
>> Shan Haitao
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
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