Re: [Xen-devel] [PATCH RFC 2/2] xen/x86: Introduce XEN_SYSCTL_cpuid hypercall

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.02.14 at 12:11, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> which permits a toolstack to execute an arbitrary cpuid instruction on a
> specified physical cpu.

For one - is it a good idea to expose the unprocessed CPUID to
any guest code? After all even the Dom0 kernel only gets to see
processed values, and the fact the without CPUID faulting apps
in PV guests can inadvertently use the raw values is known to be
a problem, not a feature.

And then - if you already have access to control operations, I
don't think you need the hyypervisor to help you: Limit your
vCPU's affinity to the particular pCPU you care about, and do
what you need doing from the kernel (by also setting the
processes affinity to the particular CPU you could achieve the
same even from user land).

Jan


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