Re: [RFC PATCH 18/33] Subarch support for CPUID instruction

From: David Miller
Date: Tue Jul 18 2006 - 16:44:08 EST

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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