On Wed, 2018-04-11 at 11:16 +0200, KarimAllah Ahmed wrote: > If the processor does not have an "Always Running APIC Timer" (aka ARAT), > we should not give guests direct access to MWAIT. The LAPIC timer would > stop ticking in deep C-states, so any host deadlines would not wakeup the > host kernel. > > The host kernel intel_idle driver handles this by switching to broadcast > mode when ARAT is not available and MWAIT is issued with a deep C-state > that would stop the LAPIC timer. When MWAIT is passed through, we can not > tell when MWAIT is issued. > > So just disable this capability when LAPIC ARAT is not available. I am not > even sure if there are any CPUs with VMX support but no LAPIC ARAT or not.
ARAT was added on WSM, so NHM, the Core 2 family and a few PSC SKUs support VMX+MWAIT but not ARAT. > Cc: Paolo Bonzini <[email protected]> > Cc: Radim Krčmář <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: H. Peter Anvin <[email protected]> > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Reported-by: Wanpeng Li <[email protected]> > Signed-off-by: KarimAllah Ahmed <[email protected]> > --- > arch/x86/kvm/x86.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index b2ff74b..0334b25 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2819,7 +2819,8 @@ static int msr_io(struct kvm_vcpu *vcpu, struct > kvm_msrs __user *user_msrs, > static inline bool kvm_can_mwait_in_guest(void) > { > return boot_cpu_has(X86_FEATURE_MWAIT) && > - !boot_cpu_has_bug(X86_BUG_MONITOR); > + !boot_cpu_has_bug(X86_BUG_MONITOR) && > + boot_cpu_has(X86_FEATURE_ARAT); > } > > int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
