Messages in this thread | | | From | Len Brown <> | Date | Mon, 29 Mar 2021 14:57:25 -0400 | Subject | Re: [PATCH v4 14/22] x86/fpu/xstate: Expand the xstate buffer on the first use of dynamic user state |
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On Mon, Mar 29, 2021 at 1:43 PM Andy Lutomirski <luto@amacapital.net> wrote:
> > *switching* XCR0 on context switch is slow, but perfectly legal. > > How slow is it? And how slow is switching XFD? XFD is definitely serializing?
XCR0 writes in a VM guest cause a VMEXIT.. XCR writes in a VM guest do not.
I will find out what the relative cost is on bare metal, where VMEXIT is not an issue. -- Len Brown, Intel Open Source Technology Center
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