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
