diff mbox series

[v2,02/10] KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch'

Message ID 20210512150945.4591-3-ilstam@amazon.com (mailing list archive)
State New, archived
Headers show
Series KVM: Implement nested TSC scaling | expand

Commit Message

Stamatis, Ilias May 12, 2021, 3:09 p.m. UTC 
Store L1's scaling ratio in that struct like we already do for L1's TSC
offset. This allows for easy save/restore when we enter and then exit
the nested guest.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/include/asm/kvm_host.h | 5 +++--
 arch/x86/kvm/x86.c              | 6 ++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

Comments

Sean Christopherson May 18, 2021, 10:52 p.m. UTC | #1 
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@amazon.com>
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---

...

> 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;
}

>  		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
>
Stamatis, Ilias May 19, 2021, 8:54 a.m. UTC | #2 
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@amazon.com>
> > Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> > ---
> 
> ...
> 
> > 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
> >
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 55efbacfc244..7dfc609eacd6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -707,7 +707,7 @@  struct kvm_vcpu_arch {
 	} st;
 
 	u64 l1_tsc_offset;
-	u64 tsc_offset;
+	u64 tsc_offset; /* current tsc offset */
 	u64 last_guest_tsc;
 	u64 last_host_tsc;
 	u64 tsc_offset_adjustment;
@@ -721,7 +721,8 @@  struct kvm_vcpu_arch {
 	u32 virtual_tsc_khz;
 	s64 ia32_tsc_adjust_msr;
 	u64 msr_ia32_power_ctl;
-	u64 tsc_scaling_ratio;
+	u64 l1_tsc_scaling_ratio;
+	u64 tsc_scaling_ratio; /* current scaling ratio */
 
 	atomic_t nmi_queued;  /* unprocessed asynchronous NMIs */
 	unsigned nmi_pending; /* NMI queued after currently running handler */
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;
 		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);