Re: [PATCH 3/6] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest_fpu()

From: H. Peter Anvin
Date: Wed Sep 19 2012 - 13:26:22 EST


On 09/19/2012 10:22 AM, Avi Kivity wrote:
>
> Note, we could also go in a different direction and make
> kernel_fpu_begin() use preempt notifiers and thus make its users
> preemptible. But that's for a separate patchset.
>

Where would you put the state if you were preempted? You want to
allocate a full extra buffer for the kernel xstate for each thread just
in case? ("Yes" is a valid answer to that question, but it is a fair
chunk of memory.)

-hpa

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