RE: [PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-08-27 Thread KY Srinivasan 
> -Original Message-
> From: Jan Beulich [mailto:jbeul...@suse.com]
> Sent: Tuesday, August 27, 2013 12:26 AM
> To: KY Srinivasan
> Cc: o...@aepfle.de; a...@canonical.com; x...@kernel.org;
> de...@linuxdriverproject.org; gre...@linuxfoundation.org;
> jasow...@redhat.com; linux-kernel@vger.kernel.org; h...@zytor.com
> Subject: Re: [PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from
> the hypervisor
> 
> >>> On 27.08.13 at 01:42, "K. Y. Srinivasan"  wrote:
> > Hyper-V supports a mechanism for retrieving the local API frequency.
> 
> "APIC"?
> 
> > @@ -27,6 +27,13 @@
> >  #define HV_X64_MSR_VP_RUNTIME_AVAILABLE(1 << 0)
> >  /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
> >  #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE(1 << 1)
> > +
> > +/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is
> available */
> > +#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1 << 11)
> > +
> > +/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
> > +#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1 << 11)
> 
> Are these two really the same bit? If so, why two different names?
> 
> > @@ -136,6 +143,12 @@
> >  /* MSR used to read the per-partition time reference counter */
> >  #define HV_X64_MSR_TIME_REF_COUNT  0x4020
> >
> > +/* MSR used to retrive the TSC frequency */
> > +#define HV_X64_MSR_TSC_FREQUENCY   0x4022
> > +
> > +/* MSR used to retrive the local APIC timer frequency */
> > +#define HV_X64_MSR_APIC_FREQUENCY  0x4023
> 
> "retrieve" (twice)?
> 
> > @@ -76,6 +77,22 @@ static void __init ms_hyperv_init_platform(void)
> > printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
> >ms_hyperv.features, ms_hyperv.hints);
> >
> > +   if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
> > +   /*
> > +* There is no need to calibrate APIC timer frequency;
> > +* nor is there a need to calibrate timer.
> > +*/
> > +   legacy_pic = _legacy_pic;
> 
> This clearly disables more than just the calibration, so the comment
> may be misleading to future readers.
> 
> > +
> > +   /*
> > +* Get the APIC frequency.
> > +*/
> > +   rdmsrl(HV_X64_MSR_APIC_FREQUENCY,
> lapic_timer_frequency);
> > +   lapic_timer_frequency /= HZ;
> 
> Is this safe? I.e. are the high 32 bits of the MSR guaranteed to
> be zero, now and forever?
> 
> > +   printk(KERN_INFO "HyperV: LAPIC Timer Frequency: 0x%x\n",
> > +   lapic_timer_frequency);
> 
> As a minor note, I generally recommend using %#x as being one
> byte shorter than the spelled out 0x%x.
> 
> Jan

Thanks Jan. I will fix the issues you have pointed out and resubmit the patch.

Regards,

K. Y
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Re: [PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-08-27 Thread Jan Beulich 
>>> On 27.08.13 at 01:42, "K. Y. Srinivasan"  wrote:
> Hyper-V supports a mechanism for retrieving the local API frequency.

"APIC"?

> @@ -27,6 +27,13 @@
>  #define HV_X64_MSR_VP_RUNTIME_AVAILABLE  (1 << 0)
>  /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
>  #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE  (1 << 1)
> +
> +/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
> +#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1 << 11)
> +
> +/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
> +#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1 << 11)

Are these two really the same bit? If so, why two different names?

> @@ -136,6 +143,12 @@
>  /* MSR used to read the per-partition time reference counter */
>  #define HV_X64_MSR_TIME_REF_COUNT0x4020
>  
> +/* MSR used to retrive the TSC frequency */
> +#define HV_X64_MSR_TSC_FREQUENCY 0x4022
> +
> +/* MSR used to retrive the local APIC timer frequency */
> +#define HV_X64_MSR_APIC_FREQUENCY0x4023

"retrieve" (twice)?

> @@ -76,6 +77,22 @@ static void __init ms_hyperv_init_platform(void)
>   printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
>  ms_hyperv.features, ms_hyperv.hints);
>  
> + if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
> + /*
> +  * There is no need to calibrate APIC timer frequency;
> +  * nor is there a need to calibrate timer.
> +  */
> + legacy_pic = _legacy_pic;

This clearly disables more than just the calibration, so the comment
may be misleading to future readers.

> +
> + /*
> +  * Get the APIC frequency.
> +  */
> + rdmsrl(HV_X64_MSR_APIC_FREQUENCY, lapic_timer_frequency);
> + lapic_timer_frequency /= HZ;

Is this safe? I.e. are the high 32 bits of the MSR guaranteed to
be zero, now and forever?

> + printk(KERN_INFO "HyperV: LAPIC Timer Frequency: 0x%x\n",
> + lapic_timer_frequency);

As a minor note, I generally recommend using %#x as being one
byte shorter than the spelled out 0x%x.

Jan

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Re: [PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-08-27 Thread Jan Beulich 
 On 27.08.13 at 01:42, K. Y. Srinivasan k...@microsoft.com wrote:
 Hyper-V supports a mechanism for retrieving the local API frequency.

APIC?

 @@ -27,6 +27,13 @@
  #define HV_X64_MSR_VP_RUNTIME_AVAILABLE  (1  0)
  /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
  #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE  (1  1)
 +
 +/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
 +#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1  11)
 +
 +/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
 +#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1  11)

Are these two really the same bit? If so, why two different names?

 @@ -136,6 +143,12 @@
  /* MSR used to read the per-partition time reference counter */
  #define HV_X64_MSR_TIME_REF_COUNT0x4020
  
 +/* MSR used to retrive the TSC frequency */
 +#define HV_X64_MSR_TSC_FREQUENCY 0x4022
 +
 +/* MSR used to retrive the local APIC timer frequency */
 +#define HV_X64_MSR_APIC_FREQUENCY0x4023

retrieve (twice)?

 @@ -76,6 +77,22 @@ static void __init ms_hyperv_init_platform(void)
   printk(KERN_INFO HyperV: features 0x%x, hints 0x%x\n,
  ms_hyperv.features, ms_hyperv.hints);
  
 + if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
 + /*
 +  * There is no need to calibrate APIC timer frequency;
 +  * nor is there a need to calibrate timer.
 +  */
 + legacy_pic = null_legacy_pic;

This clearly disables more than just the calibration, so the comment
may be misleading to future readers.

 +
 + /*
 +  * Get the APIC frequency.
 +  */
 + rdmsrl(HV_X64_MSR_APIC_FREQUENCY, lapic_timer_frequency);
 + lapic_timer_frequency /= HZ;

Is this safe? I.e. are the high 32 bits of the MSR guaranteed to
be zero, now and forever?

 + printk(KERN_INFO HyperV: LAPIC Timer Frequency: 0x%x\n,
 + lapic_timer_frequency);

As a minor note, I generally recommend using %#x as being one
byte shorter than the spelled out 0x%x.

Jan

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RE: [PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-08-27 Thread KY Srinivasan 
 -Original Message-
 From: Jan Beulich [mailto:jbeul...@suse.com]
 Sent: Tuesday, August 27, 2013 12:26 AM
 To: KY Srinivasan
 Cc: o...@aepfle.de; a...@canonical.com; x...@kernel.org;
 de...@linuxdriverproject.org; gre...@linuxfoundation.org;
 jasow...@redhat.com; linux-kernel@vger.kernel.org; h...@zytor.com
 Subject: Re: [PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from
 the hypervisor
 
  On 27.08.13 at 01:42, K. Y. Srinivasan k...@microsoft.com wrote:
  Hyper-V supports a mechanism for retrieving the local API frequency.
 
 APIC?
 
  @@ -27,6 +27,13 @@
   #define HV_X64_MSR_VP_RUNTIME_AVAILABLE(1  0)
   /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
   #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE(1  1)
  +
  +/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is
 available */
  +#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1  11)
  +
  +/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
  +#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1  11)
 
 Are these two really the same bit? If so, why two different names?
 
  @@ -136,6 +143,12 @@
   /* MSR used to read the per-partition time reference counter */
   #define HV_X64_MSR_TIME_REF_COUNT  0x4020
 
  +/* MSR used to retrive the TSC frequency */
  +#define HV_X64_MSR_TSC_FREQUENCY   0x4022
  +
  +/* MSR used to retrive the local APIC timer frequency */
  +#define HV_X64_MSR_APIC_FREQUENCY  0x4023
 
 retrieve (twice)?
 
  @@ -76,6 +77,22 @@ static void __init ms_hyperv_init_platform(void)
  printk(KERN_INFO HyperV: features 0x%x, hints 0x%x\n,
 ms_hyperv.features, ms_hyperv.hints);
 
  +   if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
  +   /*
  +* There is no need to calibrate APIC timer frequency;
  +* nor is there a need to calibrate timer.
  +*/
  +   legacy_pic = null_legacy_pic;
 
 This clearly disables more than just the calibration, so the comment
 may be misleading to future readers.
 
  +
  +   /*
  +* Get the APIC frequency.
  +*/
  +   rdmsrl(HV_X64_MSR_APIC_FREQUENCY,
 lapic_timer_frequency);
  +   lapic_timer_frequency /= HZ;
 
 Is this safe? I.e. are the high 32 bits of the MSR guaranteed to
 be zero, now and forever?
 
  +   printk(KERN_INFO HyperV: LAPIC Timer Frequency: 0x%x\n,
  +   lapic_timer_frequency);
 
 As a minor note, I generally recommend using %#x as being one
 byte shorter than the spelled out 0x%x.
 
 Jan

Thanks Jan. I will fix the issues you have pointed out and resubmit the patch.

Regards,

K. Y
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[PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-08-26 Thread K. Y. Srinivasan 
Hyper-V supports a mechanism for retrieving the local API frequency.Use this 
and bypass
the calibration code in the kernel. This would allow us to boot the Linux 
kernel as a
"modern VM" on Hyper-V where many of the legacy devices (such as PIT) are not 
emulated.

I would like to thank Olaf Hering , Jan Beulich 
 and
H. Peter Anvin  for their help in this effort.

Signed-off-by: K. Y. Srinivasan 
---
 arch/x86/include/uapi/asm/hyperv.h |   13 +
 arch/x86/kernel/cpu/mshyperv.c |   17 +
 2 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h 
b/arch/x86/include/uapi/asm/hyperv.h
index b80420b..df3d680 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -27,6 +27,13 @@
 #define HV_X64_MSR_VP_RUNTIME_AVAILABLE(1 << 0)
 /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
 #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE(1 << 1)
+
+/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
+#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1 << 11)
+
+/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
+#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1 << 11)
+
 /*
  * Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
  * and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
@@ -136,6 +143,12 @@
 /* MSR used to read the per-partition time reference counter */
 #define HV_X64_MSR_TIME_REF_COUNT  0x4020
 
+/* MSR used to retrive the TSC frequency */
+#define HV_X64_MSR_TSC_FREQUENCY   0x4022
+
+/* MSR used to retrive the local APIC timer frequency */
+#define HV_X64_MSR_APIC_FREQUENCY  0x4023
+
 /* Define the virtual APIC registers */
 #define HV_X64_MSR_EOI 0x4070
 #define HV_X64_MSR_ICR 0x4071
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 71a39f3..0593fd9 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -23,6 +23,7 @@
 #include 
 #include 
 #include 
+#include 
 
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -76,6 +77,22 @@ static void __init ms_hyperv_init_platform(void)
printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
   ms_hyperv.features, ms_hyperv.hints);
 
+   if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
+   /*
+* There is no need to calibrate APIC timer frequency;
+* nor is there a need to calibrate timer.
+*/
+   legacy_pic = _legacy_pic;
+
+   /*
+* Get the APIC frequency.
+*/
+   rdmsrl(HV_X64_MSR_APIC_FREQUENCY, lapic_timer_frequency);
+   lapic_timer_frequency /= HZ;
+   printk(KERN_INFO "HyperV: LAPIC Timer Frequency: 0x%x\n",
+   lapic_timer_frequency);
+   }
+
if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
clocksource_register_hz(_cs, NSEC_PER_SEC/100);
 }
-- 
1.7.4.1

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[PATCH 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-08-26 Thread K. Y. Srinivasan 
Hyper-V supports a mechanism for retrieving the local API frequency.Use this 
and bypass
the calibration code in the kernel. This would allow us to boot the Linux 
kernel as a
modern VM on Hyper-V where many of the legacy devices (such as PIT) are not 
emulated.

I would like to thank Olaf Hering o...@aepfle.de, Jan Beulich 
jbeul...@suse.com and
H. Peter Anvin h.peter.an...@intel.com for their help in this effort.

Signed-off-by: K. Y. Srinivasan k...@microsoft.com
---
 arch/x86/include/uapi/asm/hyperv.h |   13 +
 arch/x86/kernel/cpu/mshyperv.c |   17 +
 2 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h 
b/arch/x86/include/uapi/asm/hyperv.h
index b80420b..df3d680 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -27,6 +27,13 @@
 #define HV_X64_MSR_VP_RUNTIME_AVAILABLE(1  0)
 /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
 #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE(1  1)
+
+/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
+#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1  11)
+
+/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
+#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1  11)
+
 /*
  * Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
  * and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
@@ -136,6 +143,12 @@
 /* MSR used to read the per-partition time reference counter */
 #define HV_X64_MSR_TIME_REF_COUNT  0x4020
 
+/* MSR used to retrive the TSC frequency */
+#define HV_X64_MSR_TSC_FREQUENCY   0x4022
+
+/* MSR used to retrive the local APIC timer frequency */
+#define HV_X64_MSR_APIC_FREQUENCY  0x4023
+
 /* Define the virtual APIC registers */
 #define HV_X64_MSR_EOI 0x4070
 #define HV_X64_MSR_ICR 0x4071
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 71a39f3..0593fd9 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -23,6 +23,7 @@
 #include asm/desc.h
 #include asm/idle.h
 #include asm/irq_regs.h
+#include asm/i8259.h
 
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -76,6 +77,22 @@ static void __init ms_hyperv_init_platform(void)
printk(KERN_INFO HyperV: features 0x%x, hints 0x%x\n,
   ms_hyperv.features, ms_hyperv.hints);
 
+   if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
+   /*
+* There is no need to calibrate APIC timer frequency;
+* nor is there a need to calibrate timer.
+*/
+   legacy_pic = null_legacy_pic;
+
+   /*
+* Get the APIC frequency.
+*/
+   rdmsrl(HV_X64_MSR_APIC_FREQUENCY, lapic_timer_frequency);
+   lapic_timer_frequency /= HZ;
+   printk(KERN_INFO HyperV: LAPIC Timer Frequency: 0x%x\n,
+   lapic_timer_frequency);
+   }
+
if (ms_hyperv.features  HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
clocksource_register_hz(hyperv_cs, NSEC_PER_SEC/100);
 }
-- 
1.7.4.1

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