On 15/03/21 19:19, Maxim Levitsky wrote:
On Mon, 2021-03-15 at 18:56 +0100, Paolo Bonzini wrote:
On 15/03/21 18:43, Maxim Levitsky wrote:
+ if (!guest_cpuid_is_intel(vcpu)) {
+ /*
+ * If hardware supports Virtual VMLOAD VMSAVE then enable it
+ * in VMCB and clear intercepts to avoid #VMEXIT.
+ */
+ if (vls) {
+ svm_clr_intercept(svm, INTERCEPT_VMLOAD);
+ svm_clr_intercept(svm, INTERCEPT_VMSAVE);
+ svm->vmcb->control.virt_ext |= VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK;
+ }
+ /* No need to intercept these msrs either */
+ set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SYSENTER_EIP, 1, 1);
+ set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SYSENTER_ESP, 1, 1);
+ }
An "else" is needed here to do the opposite setup (removing the "if
(vls)" from init_vmcb).
init_vmcb currently set the INTERCEPT_VMLOAD and INTERCEPT_VMSAVE and it doesn't enable vls
There's also this towards the end of the function:
/*
* If hardware supports Virtual VMLOAD VMSAVE then enable it
* in VMCB and clear intercepts to avoid #VMEXIT.
*/
if (vls) {
svm_clr_intercept(svm, INTERCEPT_VMLOAD);
svm_clr_intercept(svm, INTERCEPT_VMSAVE);
svm->vmcb->control.virt_ext |=
VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK;
}
thus there is nothing to do if I don't want to enable vls.
It seems reasonable to me.
Both msrs I marked as '.always = false' in the
'direct_access_msrs', which makes them be intercepted by the default.
If I were to use '.always = true' it would feel a bit wrong as the intercept is not always
enabled.
I agree that .always = false is correct.
What do you think?
You can set the CPUID multiple times, so you could go from AMD to Intel
and back.
Thanks,
Paolo
