Messages in this thread | | | Date | Wed, 13 Oct 2021 17:05:44 +0200 | Subject | Re: [patch 13/31] x86/fpu: Move KVMs FPU swapping to FPU core | From | Paolo Bonzini <> |
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On 13/10/21 16:59, Andy Lutomirski wrote: >> >> Thinking more about it, #NM only has to be trapped if XCR0 enables >> a dynamic feature. In other words, the guest value of XFD can be >> limited to (host_XFD|guest_XFD) & guest_XCR0. This avoids that >> KVM unnecessarily traps for old guests that use CR0.TS. >> > You could simplify this by allocating the state the first time XCR0 > enables the feature in question. > > (This is how regular non-virt userspace*should* work too, but it > looks like I’ve probably been outvoted on that front…)
Good point, you could do that too and do the work on the XCR0 vmexit instead of #NM.
Paolo
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