[Xen-devel] Re: [RFC, PATCH 17/24] i386 Vmi msr patch

[Andi Kleen <ak@xxxxxxx>]

On Monday 13 March 2006 19:12, Zachary Amsden wrote:
> Fairly straightforward code motion of MSR / TSC / PMC accessors
> to the sub-arch level.  Note that rdmsr/wrmsr_safe functions are
> not moved; Linux relies on the fault behavior here in the event
> that certain MSRs are not supported on hardware, and combining
> this with a VMI wrapper is overly complicated.  The instructions
> are virtualizable with trap and emulate, not on critical code
> paths, and only used as part of the MSR /proc device, which is
> highly sketchy to use inside a virtual machine, but must be
> allowed as part of the compile, since it is useful on native.

I'm not aware of any MSR access being on a critical code
path on a 32bit kernel. 

And I don't think it's a good idea to virtualize the TSC 
without CPU support.

Why would you want to do any of this?

-Andi

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