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xen-devel
[Xen-devel] Re: [RFC PATCH 18/33] Subarch support for CPUID instruction
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To: |
David Miller <davem@xxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [RFC PATCH 18/33] Subarch support for CPUID instruction |
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From: |
Chris Wright <chrisw@xxxxxxxxxxxx> |
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Date: |
Tue, 18 Jul 2006 14:00:25 -0700 |
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zach@xxxxxxxxxx, akpm@xxxxxxxx, jeremy@xxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, ian.pratt@xxxxxxxxxxxxx, rusty@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, ak@xxxxxxx, chrisw@xxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxx, Christian.Limpach@xxxxxxxxxxxx, arjan@xxxxxxxxxxxxx |
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Tue, 18 Jul 2006 14:00:13 -0700 |
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* David Miller (davem@xxxxxxxxxxxxx) wrote:
> From: Zachary Amsden <zach@xxxxxxxxxx>
> Date: Tue, 18 Jul 2006 04:33:52 -0700
>
> > You really need a CPUID hook. The instruction is non-virtualizable, and
> > anything claiming to be a hypervisor really has to support masking and
> > flattening the cpuid namespace for the instruction itself. It is used
> > in assembler code and very early in boot. The alternative is injecting
> > a bunch of Xen-specific code to filter feature bits into the i386 layer,
> > which is both bad for Linux and bad for Xen - and was quite ugly in the
> > last set of Xen patches.
>
> Userspace will still see the full set of cpuid bits, since
> it can still execute cpuid unimpeded, is this ok?
Yup, it's for the kernel (things like systenter vs int 80 in vdso).
thanks,
-chris
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