On Sat, Feb 11, 2023, lirongqing@xxxxxxxxx wrote:
> From: Li RongQing <lirongqing@xxxxxxxxx>
>
> MWAIT is advertised in host is not overcommitted scenario, however,
> pvspinlock should be enabled in host overcommitted scenario. Let's
> add the MWAIT checking when enabling pvspinlock
>
> Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
> ---
> arch/x86/kernel/kvm.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 1cceac5..dfa1451 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -1087,6 +1087,11 @@ void __init kvm_spinlock_init(void)
> goto out;
> }
>
> + if (boot_cpu_has(X86_FEATURE_MWAIT)) {
IMO this is a bad idea. Odds are good that there are less-than-perfect VM configs
that advertise MONITOR+MWAIT but don't disable interception. Ugh, but we've already
added this logic for other features guaraded by KVM_HINTS_REALTIME in commit
40cd58dbf121 ("x86/kvm: Don't use PV TLB/yield when mwait is advertised")
Why doesn't the host simply advertise KVM_HINTS_REALTIME?
