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SubjectRe: [PATCH, RFC] x86-64: properly handle FPU code/data selectors
On Wed, Oct 16, 2013 at 05:13:40PM +0100, Jan Beulich wrote:
> > It preserves *less* state, because the upper 32 bits of rip are now
> > corrupted. Any 64-bit application that actually looks at the FP
> > rip/rdp fields now get the WRONG VALUES.
>
> But again - this isn't being done for ordinary 64-bit applications,
> this is only happening for KVM guests. And there not being a
> protocol for telling the caller whether a certain context hold
> 64-bit offsets or selector/offset pairs shouldn't be a reason to
> think of a solution to the problem.
>
KVM knows what mode guest vcpu is in. is_long_mode(vcpu) will tell you
if it is in long mode or not. No need to guess it.

--
Gleb.


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