Re: [Xen-devel] [PATCH v2 09/14] x86/hvm: Setup TSC scaling ratio

2015-12-10 Thread Zhang, Haozhong 
On 12/10/15 18:27, Tian, Kevin wrote:
> > From: Zhang, Haozhong
> > Sent: Monday, December 07, 2015 4:59 AM
> > 
> > This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
> > record the TSC scaling ratio, and sets it up when tsc_set_info() is
> > called for a vcpu or when a vcpu is restored or reset.
> > 
> > Signed-off-by: Haozhong Zhang 
> > ---
> >  xen/arch/x86/hvm/hvm.c| 30
> > ++
> >  xen/arch/x86/hvm/svm/svm.c|  6 --
> >  xen/arch/x86/time.c   | 13 -
> >  xen/include/asm-x86/hvm/hvm.h |  5 +
> >  xen/include/asm-x86/hvm/svm/svm.h |  3 ---
> >  xen/include/asm-x86/hvm/vcpu.h|  2 ++
> >  xen/include/asm-x86/math64.h  | 30
> > ++
> >  7 files changed, 83 insertions(+), 6 deletions(-)
> >  create mode 100644 xen/include/asm-x86/math64.h
> > 
> > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> > index 0e63c33..52a0ef8 100644
> > --- a/xen/arch/x86/hvm/hvm.c
> > +++ b/xen/arch/x86/hvm/hvm.c
> > @@ -65,6 +65,7 @@
> >  #include 
> >  #include 
> >  #include 
> > +#include 
> >  #include 
> >  #include 
> >  #include 
> > @@ -301,6 +302,29 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
> >  return 1;
> >  }
> > 
> > +void hvm_setup_tsc_scaling(struct vcpu *v)
> > +{
> > +u64 ratio;
> > +
> > +if ( !hvm_funcs.tsc_scaling_supported )
> > +return;
> > +
> > +/*
> > + * The multiplication of the first two terms may overflow a 64-bit
> > + * integer, so use mul_u64_u32_div() instead to keep precision.
> > + */
> > +ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
> > +v->domain->arch.tsc_khz, cpu_khz);
> > +
> > +if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
> > +return;
> 
> How will you check such error in other places? tsc_scaling_ratio is
> left w/ default value, while if you don't detect the issue that that
> ratio will be used for wrong scale...
>

The intention here is to fall back to the default ratio so that it
would work like no TSC scaling is used. However, I forgot here to fall
back v->domain->arch.tsc_khz and others to default values (i.e. values
used when no TSC scaling). I'll add them in the next version.

Haozhong

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Re: [Xen-devel] [PATCH v2 09/14] x86/hvm: Setup TSC scaling ratio

2015-12-10 Thread Tian, Kevin 
> From: Zhang, Haozhong
> Sent: Monday, December 07, 2015 4:59 AM
> 
> This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
> record the TSC scaling ratio, and sets it up when tsc_set_info() is
> called for a vcpu or when a vcpu is restored or reset.
> 
> Signed-off-by: Haozhong Zhang 
> ---
>  xen/arch/x86/hvm/hvm.c| 30
> ++
>  xen/arch/x86/hvm/svm/svm.c|  6 --
>  xen/arch/x86/time.c   | 13 -
>  xen/include/asm-x86/hvm/hvm.h |  5 +
>  xen/include/asm-x86/hvm/svm/svm.h |  3 ---
>  xen/include/asm-x86/hvm/vcpu.h|  2 ++
>  xen/include/asm-x86/math64.h  | 30
> ++
>  7 files changed, 83 insertions(+), 6 deletions(-)
>  create mode 100644 xen/include/asm-x86/math64.h
> 
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 0e63c33..52a0ef8 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -65,6 +65,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -301,6 +302,29 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
>  return 1;
>  }
> 
> +void hvm_setup_tsc_scaling(struct vcpu *v)
> +{
> +u64 ratio;
> +
> +if ( !hvm_funcs.tsc_scaling_supported )
> +return;
> +
> +/*
> + * The multiplication of the first two terms may overflow a 64-bit
> + * integer, so use mul_u64_u32_div() instead to keep precision.
> + */
> +ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
> +v->domain->arch.tsc_khz, cpu_khz);
> +
> +if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
> +return;

How will you check such error in other places? tsc_scaling_ratio is
left w/ default value, while if you don't detect the issue that that
ratio will be used for wrong scale...

Thanks
Kevin

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Re: [Xen-devel] [PATCH v2 09/14] x86/hvm: Setup TSC scaling ratio

2015-12-07 Thread Boris Ostrovsky 

On 12/06/2015 03:58 PM, Haozhong Zhang wrote:

This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
record the TSC scaling ratio, and sets it up when tsc_set_info() is
called for a vcpu or when a vcpu is restored or reset.

Signed-off-by: Haozhong Zhang 


Reviewed-by: Boris Ostrovsky 

with a few nits below.


---
  xen/arch/x86/hvm/hvm.c| 30 ++
  xen/arch/x86/hvm/svm/svm.c|  6 --
  xen/arch/x86/time.c   | 13 -
  xen/include/asm-x86/hvm/hvm.h |  5 +
  xen/include/asm-x86/hvm/svm/svm.h |  3 ---
  xen/include/asm-x86/hvm/vcpu.h|  2 ++
  xen/include/asm-x86/math64.h  | 30 ++
  7 files changed, 83 insertions(+), 6 deletions(-)
  create mode 100644 xen/include/asm-x86/math64.h

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0e63c33..52a0ef8 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -65,6 +65,7 @@
  #include 
  #include 
  #include 
+#include 
  #include 
  #include 
  #include 
@@ -301,6 +302,29 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
  return 1;
  }
  
+void hvm_setup_tsc_scaling(struct vcpu *v)

+{
+u64 ratio;
+
+if ( !hvm_funcs.tsc_scaling_supported )
+return;
+
+/*
+ * The multiplication of the first two terms may overflow a 64-bit
+ * integer, so use mul_u64_u32_div() instead to keep precision.
+ */
+ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
+v->domain->arch.tsc_khz, cpu_khz);
+
+if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
+return;
+
+v->arch.hvm_vcpu.tsc_scaling_ratio = ratio;
+
+if ( hvm_funcs.setup_tsc_scaling )
+hvm_funcs.setup_tsc_scaling(v);
+}
+
  void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
  {
  uint64_t tsc;
@@ -2024,6 +2048,9 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
  if ( hvm_funcs.load_cpu_ctxt(v, ) < 0 )
  return -EINVAL;
  
+if ( hvm_funcs.tsc_scaling_supported )

+hvm_setup_tsc_scaling(v);
+



I think you can drop the test here (and below) since you do the same 
check inside hvm_setup_tsc_scaling()




  v->arch.hvm_vcpu.msr_tsc_aux = ctxt.msr_tsc_aux;
  
  seg.limit = ctxt.idtr_limit;

@@ -5584,6 +5611,9 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, 
uint16_t ip)
  hvm_set_segment_register(v, x86_seg_gdtr, );
  hvm_set_segment_register(v, x86_seg_idtr, );
  
+if ( hvm_funcs.tsc_scaling_supported )

+hvm_setup_tsc_scaling(v);
+
  /* Sync AP's TSC with BSP's. */
  v->arch.hvm_vcpu.cache_tsc_offset =
  v->domain->vcpu[0]->arch.hvm_vcpu.cache_tsc_offset;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 9f741d0..d291327 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -811,7 +811,7 @@ static uint64_t svm_scale_tsc(struct vcpu *v, uint64_t tsc)
  if ( !cpu_has_tsc_ratio || d->arch.vtsc )
  return tsc;
  
-return scale_tsc(tsc, vcpu_tsc_ratio(v));

+return scale_tsc(tsc, v->arch.hvm_vcpu.tsc_scaling_ratio);
  }
  
  static uint64_t svm_get_tsc_offset(uint64_t host_tsc, uint64_t guest_tsc,

@@ -987,7 +987,7 @@ static inline void svm_tsc_ratio_save(struct vcpu *v)
  static inline void svm_tsc_ratio_load(struct vcpu *v)
  {
  if ( cpu_has_tsc_ratio && !v->domain->arch.vtsc )
-wrmsrl(MSR_AMD64_TSC_RATIO, vcpu_tsc_ratio(v));
+wrmsrl(MSR_AMD64_TSC_RATIO, v->arch.hvm_vcpu.tsc_scaling_ratio);
  }
  
  static void svm_ctxt_switch_from(struct vcpu *v)

@@ -1193,6 +1193,8 @@ static int svm_vcpu_initialise(struct vcpu *v)
  
  svm_guest_osvw_init(v);
  
+v->arch.hvm_vcpu.tsc_scaling_ratio = DEFAULT_TSC_RATIO;

+
  return 0;
  }
  
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c

index 732d1e9..d4a94eb 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1902,8 +1902,19 @@ void tsc_set_info(struct domain *d,
  if ( has_hvm_container_domain(d) )
  {
  hvm_set_rdtsc_exiting(d, d->arch.vtsc);
-if ( d->vcpu && d->vcpu[0] && incarnation == 0 )
+if ( d->vcpu && d->vcpu[0] )
  {
+ /*
+ * TSC scaling ratio on BSP is set here during initial boot, while


During domain creation rather then during boot.


+ * the same TSC scaling ratio on APs will be set in
+ * hvm_vcpu_reset_state().
+ */
+if ( !d->arch.vtsc && hvm_funcs.tsc_scaling_supported )
+hvm_setup_tsc_scaling(d->vcpu[0]);
+
+if ( incarnation )
+return;
+
  /*
   * set_tsc_offset() is called from hvm_vcpu_initialise() before
   * tsc_set_info(). New vtsc mode may require recomputing TSC
diff --git

Re: [Xen-devel] [PATCH v2 09/14] x86/hvm: Setup TSC scaling ratio

2015-12-07 Thread Haozhong Zhang 
On 12/07/15 13:42, Boris Ostrovsky wrote:
> On 12/06/2015 03:58 PM, Haozhong Zhang wrote:
> >This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
> >record the TSC scaling ratio, and sets it up when tsc_set_info() is
> >called for a vcpu or when a vcpu is restored or reset.
> >
> >Signed-off-by: Haozhong Zhang 
> 
> Reviewed-by: Boris Ostrovsky 
> 
> with a few nits below.
> 
> >---
> >  xen/arch/x86/hvm/hvm.c| 30 ++
> >  xen/arch/x86/hvm/svm/svm.c|  6 --
> >  xen/arch/x86/time.c   | 13 -
> >  xen/include/asm-x86/hvm/hvm.h |  5 +
> >  xen/include/asm-x86/hvm/svm/svm.h |  3 ---
> >  xen/include/asm-x86/hvm/vcpu.h|  2 ++
> >  xen/include/asm-x86/math64.h  | 30 ++
> >  7 files changed, 83 insertions(+), 6 deletions(-)
> >  create mode 100644 xen/include/asm-x86/math64.h
> >
> >diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> >index 0e63c33..52a0ef8 100644
> >--- a/xen/arch/x86/hvm/hvm.c
> >+++ b/xen/arch/x86/hvm/hvm.c
> >@@ -65,6 +65,7 @@
> >  #include 
> >  #include 
> >  #include 
> >+#include 
> >  #include 
> >  #include 
> >  #include 
> >@@ -301,6 +302,29 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
> >  return 1;
> >  }
> >+void hvm_setup_tsc_scaling(struct vcpu *v)
> >+{
> >+u64 ratio;
> >+
> >+if ( !hvm_funcs.tsc_scaling_supported )
> >+return;
> >+
> >+/*
> >+ * The multiplication of the first two terms may overflow a 64-bit
> >+ * integer, so use mul_u64_u32_div() instead to keep precision.
> >+ */
> >+ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
> >+v->domain->arch.tsc_khz, cpu_khz);
> >+
> >+if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
> >+return;
> >+
> >+v->arch.hvm_vcpu.tsc_scaling_ratio = ratio;
> >+
> >+if ( hvm_funcs.setup_tsc_scaling )
> >+hvm_funcs.setup_tsc_scaling(v);
> >+}
> >+
> >  void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
> >  {
> >  uint64_t tsc;
> >@@ -2024,6 +2048,9 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
> >hvm_domain_context_t *h)
> >  if ( hvm_funcs.load_cpu_ctxt(v, ) < 0 )
> >  return -EINVAL;
> >+if ( hvm_funcs.tsc_scaling_supported )
> >+hvm_setup_tsc_scaling(v);
> >+
> 
> 
> I think you can drop the test here (and below) since you do the same check
> inside hvm_setup_tsc_scaling()
>

Yes, the check here is redundant.

> 
> >  v->arch.hvm_vcpu.msr_tsc_aux = ctxt.msr_tsc_aux;
> >  seg.limit = ctxt.idtr_limit;
> >@@ -5584,6 +5611,9 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, 
> >uint16_t ip)
> >  hvm_set_segment_register(v, x86_seg_gdtr, );
> >  hvm_set_segment_register(v, x86_seg_idtr, );
> >+if ( hvm_funcs.tsc_scaling_supported )
> >+hvm_setup_tsc_scaling(v);
> >+
> >  /* Sync AP's TSC with BSP's. */
> >  v->arch.hvm_vcpu.cache_tsc_offset =
> >  v->domain->vcpu[0]->arch.hvm_vcpu.cache_tsc_offset;
> >diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> >index 9f741d0..d291327 100644
> >--- a/xen/arch/x86/hvm/svm/svm.c
> >+++ b/xen/arch/x86/hvm/svm/svm.c
> >@@ -811,7 +811,7 @@ static uint64_t svm_scale_tsc(struct vcpu *v, uint64_t 
> >tsc)
> >  if ( !cpu_has_tsc_ratio || d->arch.vtsc )
> >  return tsc;
> >-return scale_tsc(tsc, vcpu_tsc_ratio(v));
> >+return scale_tsc(tsc, v->arch.hvm_vcpu.tsc_scaling_ratio);
> >  }
> >  static uint64_t svm_get_tsc_offset(uint64_t host_tsc, uint64_t guest_tsc,
> >@@ -987,7 +987,7 @@ static inline void svm_tsc_ratio_save(struct vcpu *v)
> >  static inline void svm_tsc_ratio_load(struct vcpu *v)
> >  {
> >  if ( cpu_has_tsc_ratio && !v->domain->arch.vtsc )
> >-wrmsrl(MSR_AMD64_TSC_RATIO, vcpu_tsc_ratio(v));
> >+wrmsrl(MSR_AMD64_TSC_RATIO, v->arch.hvm_vcpu.tsc_scaling_ratio);
> >  }
> >  static void svm_ctxt_switch_from(struct vcpu *v)
> >@@ -1193,6 +1193,8 @@ static int svm_vcpu_initialise(struct vcpu *v)
> >  svm_guest_osvw_init(v);
> >+v->arch.hvm_vcpu.tsc_scaling_ratio = DEFAULT_TSC_RATIO;
> >+
> >  return 0;
> >  }
> >diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
> >index 732d1e9..d4a94eb 100644
> >--- a/xen/arch/x86/time.c
> >+++ b/xen/arch/x86/time.c
> >@@ -1902,8 +1902,19 @@ void tsc_set_info(struct domain *d,
> >  if ( has_hvm_container_domain(d) )
> >  {
> >  hvm_set_rdtsc_exiting(d, d->arch.vtsc);
> >-if ( d->vcpu && d->vcpu[0] && incarnation == 0 )
> >+if ( d->vcpu && d->vcpu[0] )
> >  {
> >+ /*
> >+ * TSC scaling ratio on BSP is set here during initial boot, 
> >while
> 
> During domain creation rather then during boot.
>

Yes, will change.

> >+ * the same TSC scaling ratio on APs will be set in
> >+ *

[Xen-devel] [PATCH v2 09/14] x86/hvm: Setup TSC scaling ratio

2015-12-06 Thread Haozhong Zhang 
This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
record the TSC scaling ratio, and sets it up when tsc_set_info() is
called for a vcpu or when a vcpu is restored or reset.

Signed-off-by: Haozhong Zhang 
---
 xen/arch/x86/hvm/hvm.c| 30 ++
 xen/arch/x86/hvm/svm/svm.c|  6 --
 xen/arch/x86/time.c   | 13 -
 xen/include/asm-x86/hvm/hvm.h |  5 +
 xen/include/asm-x86/hvm/svm/svm.h |  3 ---
 xen/include/asm-x86/hvm/vcpu.h|  2 ++
 xen/include/asm-x86/math64.h  | 30 ++
 7 files changed, 83 insertions(+), 6 deletions(-)
 create mode 100644 xen/include/asm-x86/math64.h

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0e63c33..52a0ef8 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -65,6 +65,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -301,6 +302,29 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
 return 1;
 }
 
+void hvm_setup_tsc_scaling(struct vcpu *v)
+{
+u64 ratio;
+
+if ( !hvm_funcs.tsc_scaling_supported )
+return;
+
+/*
+ * The multiplication of the first two terms may overflow a 64-bit
+ * integer, so use mul_u64_u32_div() instead to keep precision.
+ */
+ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
+v->domain->arch.tsc_khz, cpu_khz);
+
+if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
+return;
+
+v->arch.hvm_vcpu.tsc_scaling_ratio = ratio;
+
+if ( hvm_funcs.setup_tsc_scaling )
+hvm_funcs.setup_tsc_scaling(v);
+}
+
 void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
 {
 uint64_t tsc;
@@ -2024,6 +2048,9 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
 if ( hvm_funcs.load_cpu_ctxt(v, ) < 0 )
 return -EINVAL;
 
+if ( hvm_funcs.tsc_scaling_supported )
+hvm_setup_tsc_scaling(v);
+
 v->arch.hvm_vcpu.msr_tsc_aux = ctxt.msr_tsc_aux;
 
 seg.limit = ctxt.idtr_limit;
@@ -5584,6 +5611,9 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, 
uint16_t ip)
 hvm_set_segment_register(v, x86_seg_gdtr, );
 hvm_set_segment_register(v, x86_seg_idtr, );
 
+if ( hvm_funcs.tsc_scaling_supported )
+hvm_setup_tsc_scaling(v);
+
 /* Sync AP's TSC with BSP's. */
 v->arch.hvm_vcpu.cache_tsc_offset =
 v->domain->vcpu[0]->arch.hvm_vcpu.cache_tsc_offset;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 9f741d0..d291327 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -811,7 +811,7 @@ static uint64_t svm_scale_tsc(struct vcpu *v, uint64_t tsc)
 if ( !cpu_has_tsc_ratio || d->arch.vtsc )
 return tsc;
 
-return scale_tsc(tsc, vcpu_tsc_ratio(v));
+return scale_tsc(tsc, v->arch.hvm_vcpu.tsc_scaling_ratio);
 }
 
 static uint64_t svm_get_tsc_offset(uint64_t host_tsc, uint64_t guest_tsc,
@@ -987,7 +987,7 @@ static inline void svm_tsc_ratio_save(struct vcpu *v)
 static inline void svm_tsc_ratio_load(struct vcpu *v)
 {
 if ( cpu_has_tsc_ratio && !v->domain->arch.vtsc ) 
-wrmsrl(MSR_AMD64_TSC_RATIO, vcpu_tsc_ratio(v));
+wrmsrl(MSR_AMD64_TSC_RATIO, v->arch.hvm_vcpu.tsc_scaling_ratio);
 }
 
 static void svm_ctxt_switch_from(struct vcpu *v)
@@ -1193,6 +1193,8 @@ static int svm_vcpu_initialise(struct vcpu *v)
 
 svm_guest_osvw_init(v);
 
+v->arch.hvm_vcpu.tsc_scaling_ratio = DEFAULT_TSC_RATIO;
+
 return 0;
 }
 
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 732d1e9..d4a94eb 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1902,8 +1902,19 @@ void tsc_set_info(struct domain *d,
 if ( has_hvm_container_domain(d) )
 {
 hvm_set_rdtsc_exiting(d, d->arch.vtsc);
-if ( d->vcpu && d->vcpu[0] && incarnation == 0 )
+if ( d->vcpu && d->vcpu[0] )
 {
+ /*
+ * TSC scaling ratio on BSP is set here during initial boot, while
+ * the same TSC scaling ratio on APs will be set in
+ * hvm_vcpu_reset_state().
+ */
+if ( !d->arch.vtsc && hvm_funcs.tsc_scaling_supported )
+hvm_setup_tsc_scaling(d->vcpu[0]);
+
+if ( incarnation )
+return;
+
 /*
  * set_tsc_offset() is called from hvm_vcpu_initialise() before
  * tsc_set_info(). New vtsc mode may require recomputing TSC
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 8b10a67..e74524e 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -226,6 +226,9 @@ struct hvm_function_table {
 int (*altp2m_vcpu_emulate_vmfunc)(struct cpu_user_regs *regs);
 
 uint64_t (*scale_tsc)(struct vcpu *v, uint64_t tsc);
+
+/* Architecture function to setup TSC scaling