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xen-devel
[Xen-devel] Re: [RFC PATCH 18/33] Subarch support for CPUID instruction
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zach@xxxxxxxxxx |
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Subject: |
[Xen-devel] Re: [RFC PATCH 18/33] Subarch support for CPUID instruction |
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From: |
David Miller <davem@xxxxxxxxxxxxx> |
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Date: |
Tue, 18 Jul 2006 13:46:25 -0700 (PDT) |
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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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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?
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