linux-kernel - Re: [Xen-devel] [PATCH 10/24] xen: mask XSAVE from cpuid

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Message-ID: <20090316072904.733e7e43@infradead.org>
Date:	Mon, 16 Mar 2009 07:29:04 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	"Jeremy Fitzhardinge" <jeremy.fitzhardinge@...rix.com>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	"Xen-devel" <xen-devel@...ts.xensource.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [Xen-devel] [PATCH 10/24] xen: mask XSAVE from cpuid

On Mon, 16 Mar 2009 14:16:32 +0000
"Jan Beulich" <jbeulich@...ell.com> wrote:

> >>> Arjan van de Ven <arjan@...radead.org> 16.03.09 01:09 >>>
> >Well.. pretty much all new instructions need Xen modifications due to
> >the need to be emulate to deal with traps/vmexits/etc right? 
> >So I don't quite see many cpuid bits that would NOT involve some Xen
> >modification or another ;)
> 
> No, new (user-mode accessible) instructions represent precisely the
> kind of extension that do not require hypervisor (or OS) awareness
> (see SSE2 etc, AES, FMA). 

so Xen doesn't need to handle a case where the kernel does AES on
uncached IO memory ?


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
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