On Tue, 2021-05-18 at 22:52 +0000, Sean Christopherson wrote:
> On Wed, May 12, 2021, Ilias Stamatis wrote:
> > Store L1's scaling ratio in that struct like we already do for L1's TSC
>
> s/that struct/kvm_vcpu_arch. Forcing the reader to look at the subject to
> understand the changelog is annoying, especially when it saves all of a handful
> of characters. E.g. I often read patches without the subject in scope.
>
> > offset. This allows for easy save/restore when we enter and then exit
> > the nested guest.
> >
> > Signed-off-by: Ilias Stamatis <ilstam@xxxxxxxxxx>
> > Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> > ---
>
> ...
>
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 9b6bca616929..07cf5d7ece38 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2185,6 +2185,7 @@ static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
> >
> > /* Guest TSC same frequency as host TSC? */
> > if (!scale) {
> > + vcpu->arch.l1_tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
> > vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
>
> Looks like these are always set as a pair, maybe add a helper, e.g.
>
> static void kvm_set_l1_tsc_scaling_ratio(u64 ratio)
> {
> vcpu->arch.l1_tsc_scaling_ratio = ratio;
> vcpu->arch.tsc_scaling_ratio = ratio;
> }
>
Hmm, they are not *always* set as a pair. Plus wouldn't this name be a bit
misleading suggesting that L1's scaling ratio is updated but implicitly
changing the current ratio too?
I'm not sure a helper function would add much
value here.
> > return 0;
> > }
> > @@ -2211,7 +2212,7 @@ static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
> > return -1;
> > }
> >
> > - vcpu->arch.tsc_scaling_ratio = ratio;
> > + vcpu->arch.l1_tsc_scaling_ratio = vcpu->arch.tsc_scaling_ratio = ratio;
> > return 0;
> > }
> >
> > @@ -2223,6 +2224,7 @@ static int kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz)
> > /* tsc_khz can be zero if TSC calibration fails */
> > if (user_tsc_khz == 0) {
> > /* set tsc_scaling_ratio to a safe value */
> > + vcpu->arch.l1_tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
> > vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
> > return -1;
> > }
> > @@ -2459,7 +2461,7 @@ static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu,
> >
> > static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
> > {
> > - if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio)
> > + if (vcpu->arch.l1_tsc_scaling_ratio != kvm_default_tsc_scaling_ratio)
> > WARN_ON(adjustment < 0);
> > adjustment = kvm_scale_tsc(vcpu, (u64) adjustment);
> > adjust_tsc_offset_guest(vcpu, adjustment);
> > --
> > 2.17.1
> >
