[PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[K. Y. Srinivasan]

Hyper-V supports a mechanism for retrieving the local APIC 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 <olaf@aepfle.de>, Jan Beulich <JBeulich@suse.com> and
H. Peter Anvin <h.peter.anvin@intel.com> for their help in this effort.

In this version of the patch, I have addressed Jan's comments.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 arch/x86/include/uapi/asm/hyperv.h |   19 +++++++++++++++++++
 arch/x86/kernel/cpu/mshyperv.c     |   24 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index b80420b..b8f1c01 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -27,6 +27,19 @@
 #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)
+
+/*
+ * There is a single feature flag that signifies the presence of the MSR
+ * that can be used to retrieve both the local APIC Timer frequency as
+ * well as the TSC frequency.
+ */
+
+/* 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 +149,12 @@
 /* MSR used to read the per-partition time reference counter */
 #define HV_X64_MSR_TIME_REF_COUNT		0x40000020
 
+/* MSR used to retrieve the TSC frequency */
+#define HV_X64_MSR_TSC_FREQUENCY		0x40000022
+
+/* MSR used to retrieve the local APIC timer frequency */
+#define HV_X64_MSR_APIC_FREQUENCY		0x40000023
+
 /* Define the virtual APIC registers */
 #define HV_X64_MSR_EOI				0x40000070
 #define HV_X64_MSR_ICR				0x40000071
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 71a39f3..b3dc639 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -15,6 +15,7 @@
 #include <linux/clocksource.h>
 #include <linux/module.h>
 #include <linux/hardirq.h>
+#include <linux/efi.h>
 #include <linux/interrupt.h>
 #include <asm/processor.h>
 #include <asm/hypervisor.h>
@@ -23,6 +24,7 @@
 #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);
@@ -67,6 +69,8 @@ static struct clocksource hyperv_cs = {
 
 static void __init ms_hyperv_init_platform(void)
 {
+	u64	hv_lapic_frequency;
+
 	/*
 	 * Extract the features and hints
 	 */
@@ -76,6 +80,26 @@ 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) {
+		/*
+		 * Get the APIC frequency.
+		 */
+		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
+		hv_lapic_frequency /= HZ;
+		lapic_timer_frequency = hv_lapic_frequency;
+		printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
+				lapic_timer_frequency);
+
+		/*
+		 * On Hyper-V, when we are booting off an EFI firmware stack,
+		 * we do not have many legacy devices including PIC, PIT etc.
+		 */
+		if (efi_enabled(EFI_BOOT)) {
+			printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
+			legacy_pic = &null_legacy_pic;
+		}
+	}
+
 	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
 		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
 }
-- 
1.7.4.1

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Jan Beulich]

>>> On 03.09.13 at 20:30, "K. Y. Srinivasan" <kys@microsoft.com> wrote:
> @@ -76,6 +80,26 @@ 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) {
> +		/*
> +		 * Get the APIC frequency.
> +		 */
> +		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
> +		hv_lapic_frequency /= HZ;
> +		lapic_timer_frequency = hv_lapic_frequency;
> +		printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
> +				lapic_timer_frequency);
> +
> +		/*
> +		 * On Hyper-V, when we are booting off an EFI firmware stack,
> +		 * we do not have many legacy devices including PIC, PIT etc.
> +		 */
> +		if (efi_enabled(EFI_BOOT)) {
> +			printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
> +			legacy_pic = &null_legacy_pic;
> +		}

And this check is really connected to the feature check around the
whole block, rather than being independent? (I'd also think that
this latter message would suffice to be KERN_DEBUG).

Jan

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Gleb Natapov]

On Tue, Sep 03, 2013 at 11:30:23AM -0700, K. Y. Srinivasan wrote:
> Hyper-V supports a mechanism for retrieving the local APIC 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 <olaf@aepfle.de>, Jan Beulich <JBeulich@suse.com> and
> H. Peter Anvin <h.peter.anvin@intel.com> for their help in this effort.
> 
> In this version of the patch, I have addressed Jan's comments.
> 
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  arch/x86/include/uapi/asm/hyperv.h |   19 +++++++++++++++++++
>  arch/x86/kernel/cpu/mshyperv.c     |   24 ++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
> index b80420b..b8f1c01 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -27,6 +27,19 @@
>  #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)
> +
> +/*
> + * There is a single feature flag that signifies the presence of the MSR
> + * that can be used to retrieve both the local APIC Timer frequency as
> + * well as the TSC frequency.
> + */
> +
> +/* 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 +149,12 @@
>  /* MSR used to read the per-partition time reference counter */
>  #define HV_X64_MSR_TIME_REF_COUNT		0x40000020
>  
> +/* MSR used to retrieve the TSC frequency */
> +#define HV_X64_MSR_TSC_FREQUENCY		0x40000022
> +
You do not use this MSR in the patch, but in general how it suppose to
work during migration if host TSC frequency changes?

> +/* MSR used to retrieve the local APIC timer frequency */
> +#define HV_X64_MSR_APIC_FREQUENCY		0x40000023
> +
>  /* Define the virtual APIC registers */
>  #define HV_X64_MSR_EOI				0x40000070
>  #define HV_X64_MSR_ICR				0x40000071
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 71a39f3..b3dc639 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -15,6 +15,7 @@
>  #include <linux/clocksource.h>
>  #include <linux/module.h>
>  #include <linux/hardirq.h>
> +#include <linux/efi.h>
>  #include <linux/interrupt.h>
>  #include <asm/processor.h>
>  #include <asm/hypervisor.h>
> @@ -23,6 +24,7 @@
>  #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);
> @@ -67,6 +69,8 @@ static struct clocksource hyperv_cs = {
>  
>  static void __init ms_hyperv_init_platform(void)
>  {
> +	u64	hv_lapic_frequency;
> +
>  	/*
>  	 * Extract the features and hints
>  	 */
> @@ -76,6 +80,26 @@ 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) {
> +		/*
> +		 * Get the APIC frequency.
> +		 */
> +		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
> +		hv_lapic_frequency /= HZ;
> +		lapic_timer_frequency = hv_lapic_frequency;
> +		printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
> +				lapic_timer_frequency);
> +
> +		/*
> +		 * On Hyper-V, when we are booting off an EFI firmware stack,
> +		 * we do not have many legacy devices including PIC, PIT etc.
> +		 */
> +		if (efi_enabled(EFI_BOOT)) {
> +			printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
> +			legacy_pic = &null_legacy_pic;
> +		}
> +	}
> +
>  	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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--
			Gleb.

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Wednesday, September 04, 2013 12:17 AM
> To: KY Srinivasan
> Cc: olaf@aepfle.de; bp@alien8.de; apw@canonical.com; x86@kernel.org;
> tglx@linutronix.de; devel@linuxdriverproject.org; gregkh@linuxfoundation.org;
> jasowang@redhat.com; linux-kernel@vger.kernel.org; hpa@zytor.com
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> >>> On 03.09.13 at 20:30, "K. Y. Srinivasan" <kys@microsoft.com> wrote:
> > @@ -76,6 +80,26 @@ 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) {
> > +		/*
> > +		 * Get the APIC frequency.
> > +		 */
> > +		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
> > +		hv_lapic_frequency /= HZ;
> > +		lapic_timer_frequency = hv_lapic_frequency;
> > +		printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
> > +				lapic_timer_frequency);
> > +
> > +		/*
> > +		 * On Hyper-V, when we are booting off an EFI firmware stack,
> > +		 * we do not have many legacy devices including PIC, PIT etc.
> > +		 */
> > +		if (efi_enabled(EFI_BOOT)) {
> > +			printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
> > +			legacy_pic = &null_legacy_pic;
> > +		}
> 
> And this check is really connected to the feature check around the
> whole block, rather than being independent? (I'd also think that
> this latter message would suffice to be KERN_DEBUG).

I felt it was safer to first check for the feature  since if the feature is not
there, we need to calibrate based on PIT. Furthermore, the feature is available
even in legacy environments when we are not booting on an EFI stack.

Regards,

K. Y

> 
> Jan

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: Gleb Natapov [mailto:gleb@redhat.com]
> Sent: Wednesday, September 04, 2013 2:40 AM
> To: KY Srinivasan
> Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com; tglx@linutronix.de; hpa@zytor.com;
> JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On Tue, Sep 03, 2013 at 11:30:23AM -0700, K. Y. Srinivasan wrote:
> > Hyper-V supports a mechanism for retrieving the local APIC 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 <olaf@aepfle.de>, Jan Beulich
> <JBeulich@suse.com> and
> > H. Peter Anvin <h.peter.anvin@intel.com> for their help in this effort.
> >
> > In this version of the patch, I have addressed Jan's comments.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> >  arch/x86/include/uapi/asm/hyperv.h |   19 +++++++++++++++++++
> >  arch/x86/kernel/cpu/mshyperv.c     |   24 ++++++++++++++++++++++++
> >  2 files changed, 43 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> > index b80420b..b8f1c01 100644
> > --- a/arch/x86/include/uapi/asm/hyperv.h
> > +++ b/arch/x86/include/uapi/asm/hyperv.h
> > @@ -27,6 +27,19 @@
> >  #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)
> > +
> > +/*
> > + * There is a single feature flag that signifies the presence of the MSR
> > + * that can be used to retrieve both the local APIC Timer frequency as
> > + * well as the TSC frequency.
> > + */
> > +
> > +/* 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 +149,12 @@
> >  /* MSR used to read the per-partition time reference counter */
> >  #define HV_X64_MSR_TIME_REF_COUNT		0x40000020
> >
> > +/* MSR used to retrieve the TSC frequency */
> > +#define HV_X64_MSR_TSC_FREQUENCY		0x40000022
> > +
> You do not use this MSR in the patch, but in general how it suppose to
> work during migration if host TSC frequency changes?

TSC related migration issues are distinct from how we calibrate the TSC frequency. This MSR
allows you to retrieve the TSC frequency without having to do explicit calibration.

To address the migration issues; the hypervisor provides additional information on the host
that you are running that can be used to compensate for differences in TSC across hosts.  

Regards,

K. Y

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Gleb Natapov]

On Wed, Sep 04, 2013 at 03:16:30PM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Gleb Natapov [mailto:gleb@redhat.com]
> > Sent: Wednesday, September 04, 2013 2:40 AM
> > To: KY Srinivasan
> > Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> > devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> > jasowang@redhat.com; tglx@linutronix.de; hpa@zytor.com;
> > JBeulich@suse.com; bp@alien8.de
> > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> > from the hypervisor
> > 
> > On Tue, Sep 03, 2013 at 11:30:23AM -0700, K. Y. Srinivasan wrote:
> > > Hyper-V supports a mechanism for retrieving the local APIC 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 <olaf@aepfle.de>, Jan Beulich
> > <JBeulich@suse.com> and
> > > H. Peter Anvin <h.peter.anvin@intel.com> for their help in this effort.
> > >
> > > In this version of the patch, I have addressed Jan's comments.
> > >
> > > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > > ---
> > >  arch/x86/include/uapi/asm/hyperv.h |   19 +++++++++++++++++++
> > >  arch/x86/kernel/cpu/mshyperv.c     |   24 ++++++++++++++++++++++++
> > >  2 files changed, 43 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/arch/x86/include/uapi/asm/hyperv.h
> > b/arch/x86/include/uapi/asm/hyperv.h
> > > index b80420b..b8f1c01 100644
> > > --- a/arch/x86/include/uapi/asm/hyperv.h
> > > +++ b/arch/x86/include/uapi/asm/hyperv.h
> > > @@ -27,6 +27,19 @@
> > >  #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)
> > > +
> > > +/*
> > > + * There is a single feature flag that signifies the presence of the MSR
> > > + * that can be used to retrieve both the local APIC Timer frequency as
> > > + * well as the TSC frequency.
> > > + */
> > > +
> > > +/* 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 +149,12 @@
> > >  /* MSR used to read the per-partition time reference counter */
> > >  #define HV_X64_MSR_TIME_REF_COUNT		0x40000020
> > >
> > > +/* MSR used to retrieve the TSC frequency */
> > > +#define HV_X64_MSR_TSC_FREQUENCY		0x40000022
> > > +
> > You do not use this MSR in the patch, but in general how it suppose to
> > work during migration if host TSC frequency changes?
> 
> TSC related migration issues are distinct from how we calibrate the TSC frequency. This MSR
> allows you to retrieve the TSC frequency without having to do explicit calibration.
> 
But the value retrieved can be obsolete by the time guest sues it due to
migration.

> To address the migration issues; the hypervisor provides additional information on the host
> that you are running that can be used to compensate for differences in TSC across hosts.  
> 
Are you referring to "Reference TSC Page" here?

--
			Gleb.

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: K. Y. Srinivasan [mailto:kys@microsoft.com]
> Sent: Tuesday, September 03, 2013 11:30 AM
> To: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com; tglx@linutronix.de; hpa@zytor.com;
> JBeulich@suse.com; bp@alien8.de
> Cc: KY Srinivasan
> Subject: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from
> the hypervisor
> 
> Hyper-V supports a mechanism for retrieving the local APIC 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 <olaf@aepfle.de>, Jan Beulich
> <JBeulich@suse.com> and
> H. Peter Anvin <h.peter.anvin@intel.com> for their help in this effort.
> 
> In this version of the patch, I have addressed Jan's comments.
> 
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  arch/x86/include/uapi/asm/hyperv.h |   19 +++++++++++++++++++
>  arch/x86/kernel/cpu/mshyperv.c     |   24 ++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> index b80420b..b8f1c01 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -27,6 +27,19 @@
>  #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)
> +
> +/*
> + * There is a single feature flag that signifies the presence of the MSR
> + * that can be used to retrieve both the local APIC Timer frequency as
> + * well as the TSC frequency.
> + */
> +
> +/* 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 +149,12 @@
>  /* MSR used to read the per-partition time reference counter */
>  #define HV_X64_MSR_TIME_REF_COUNT		0x40000020
> 
> +/* MSR used to retrieve the TSC frequency */
> +#define HV_X64_MSR_TSC_FREQUENCY		0x40000022
> +
> +/* MSR used to retrieve the local APIC timer frequency */
> +#define HV_X64_MSR_APIC_FREQUENCY		0x40000023
> +
>  /* Define the virtual APIC registers */
>  #define HV_X64_MSR_EOI				0x40000070
>  #define HV_X64_MSR_ICR				0x40000071
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 71a39f3..b3dc639 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -15,6 +15,7 @@
>  #include <linux/clocksource.h>
>  #include <linux/module.h>
>  #include <linux/hardirq.h>
> +#include <linux/efi.h>
>  #include <linux/interrupt.h>
>  #include <asm/processor.h>
>  #include <asm/hypervisor.h>
> @@ -23,6 +24,7 @@
>  #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);
> @@ -67,6 +69,8 @@ static struct clocksource hyperv_cs = {
> 
>  static void __init ms_hyperv_init_platform(void)
>  {
> +	u64	hv_lapic_frequency;
> +
>  	/*
>  	 * Extract the features and hints
>  	 */
> @@ -76,6 +80,26 @@ 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) {
> +		/*
> +		 * Get the APIC frequency.
> +		 */
> +		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
> +		hv_lapic_frequency /= HZ;
> +		lapic_timer_frequency = hv_lapic_frequency;
> +		printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
> +				lapic_timer_frequency);
> +
> +		/*
> +		 * On Hyper-V, when we are booting off an EFI firmware stack,
> +		 * we do not have many legacy devices including PIC, PIT etc.
> +		 */
> +		if (efi_enabled(EFI_BOOT)) {
> +			printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
> +			legacy_pic = &null_legacy_pic;
> +		}
> +	}
> +
>  	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
>  		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
>  }
> --
> 1.7.4.1

Peter,

Let me know if you want me to address any additional issues in this patch.


Regards,

K. Y

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[H. Peter Anvin]

On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> 
> Peter,
> 
> Let me know if you want me to address any additional issues in this patch.
> 

Please address Jan and Gleb's feedback.

	-hpa

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: H. Peter Anvin [mailto:hpa@zytor.com]
> Sent: Thursday, September 12, 2013 5:28 PM
> To: KY Srinivasan
> Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> >
> > Peter,
> >
> > Let me know if you want me to address any additional issues in this patch.
> >
> 
> Please address Jan and Gleb's feedback.

Gleb's feedback was a question and I answered that as I did Jan's feedback as well.
Gleb, Jan, please let me know if there is something else you want addressed here.

Regards,

K. Y

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Jan Beulich]

>>> On 13.09.13 at 03:43, KY Srinivasan <kys@microsoft.com> wrote:

> 
>> -----Original Message-----
>> From: H. Peter Anvin [mailto:hpa@zytor.com]
>> Sent: Thursday, September 12, 2013 5:28 PM
>> To: KY Srinivasan
>> Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
>> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
>> jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com; bp@alien8.de 
>> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
>> from the hypervisor
>> 
>> On 09/12/2013 05:06 PM, KY Srinivasan wrote:
>> >
>> > Peter,
>> >
>> > Let me know if you want me to address any additional issues in this patch.
>> >
>> 
>> Please address Jan and Gleb's feedback.
> 
> Gleb's feedback was a question and I answered that as I did Jan's feedback 
> as well.
> Gleb, Jan, please let me know if there is something else you want addressed 
> here.

Indeed, apart from the question whether to change that one
message's level from KERN_INFO to KERN_DEBUG, there was
nothing really left unexplained (the aspect of the artificial tying
together of distinct features is really something KY has to
decide - I merely tried to point out that this is odd).

Jan

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Gleb Natapov]

On Fri, Sep 13, 2013 at 01:43:09AM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: H. Peter Anvin [mailto:hpa@zytor.com]
> > Sent: Thursday, September 12, 2013 5:28 PM
> > To: KY Srinivasan
> > Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> > devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> > jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com; bp@alien8.de
> > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> > from the hypervisor
> > 
> > On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> > >
> > > Peter,
> > >
> > > Let me know if you want me to address any additional issues in this patch.
> > >
> > 
> > Please address Jan and Gleb's feedback.
> 
> Gleb's feedback was a question and I answered that as I did Jan's feedback as well.
> Gleb, Jan, please let me know if there is something else you want addressed here.
> 
No, I am just interesting to know some details about the interface since
I cannot find it documented in Hyper-V spec.

--
			Gleb.

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Thursday, September 12, 2013 11:39 PM
> To: KY Srinivasan; H. Peter Anvin
> Cc: olaf@aepfle.de; bp@alien8.de; apw@canonical.com; x86@kernel.org;
> tglx@linutronix.de; devel@linuxdriverproject.org; gregkh@linuxfoundation.org;
> jasowang@redhat.com; linux-kernel@vger.kernel.org
> Subject: RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> >>> On 13.09.13 at 03:43, KY Srinivasan <kys@microsoft.com> wrote:
> 
> >
> >> -----Original Message-----
> >> From: H. Peter Anvin [mailto:hpa@zytor.com]
> >> Sent: Thursday, September 12, 2013 5:28 PM
> >> To: KY Srinivasan
> >> Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org;
> >> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> >> jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com;
> bp@alien8.de
> >> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> >> from the hypervisor
> >>
> >> On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> >> >
> >> > Peter,
> >> >
> >> > Let me know if you want me to address any additional issues in this patch.
> >> >
> >>
> >> Please address Jan and Gleb's feedback.
> >
> > Gleb's feedback was a question and I answered that as I did Jan's feedback
> > as well.
> > Gleb, Jan, please let me know if there is something else you want addressed
> > here.
> 
> Indeed, apart from the question whether to change that one
> message's level from KERN_INFO to KERN_DEBUG, there was
> nothing really left unexplained (the aspect of the artificial tying
> together of distinct features is really something KY has to
> decide - I merely tried to point out that this is odd).

Thanks Jan. Peter, if it is ok with you, I would like to keep the message
level at KERN_INFO.

Regards,

K. Y

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: Gleb Natapov [mailto:gleb@redhat.com]
> Sent: Friday, September 13, 2013 2:55 AM
> To: KY Srinivasan
> Cc: H. Peter Anvin; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On Fri, Sep 13, 2013 at 01:43:09AM +0000, KY Srinivasan wrote:
> >
> >
> > > -----Original Message-----
> > > From: H. Peter Anvin [mailto:hpa@zytor.com]
> > > Sent: Thursday, September 12, 2013 5:28 PM
> > > To: KY Srinivasan
> > > Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org;
> > > devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> > > jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com;
> bp@alien8.de
> > > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> > > from the hypervisor
> > >
> > > On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> > > >
> > > > Peter,
> > > >
> > > > Let me know if you want me to address any additional issues in this patch.
> > > >
> > >
> > > Please address Jan and Gleb's feedback.
> >
> > Gleb's feedback was a question and I answered that as I did Jan's feedback as
> well.
> > Gleb, Jan, please let me know if there is something else you want addressed
> here.
> >
> No, I am just interesting to know some details about the interface since
> I cannot find it documented in Hyper-V spec.

Thanks Gleb. Here is the link for the latest Hyper-V specification:
http://www.microsoft.com/en-us/download/details.aspx?id=39289

This spec talks about how migration is handled with regards to TSC.

Peter, if you are ok with the message level, there is no other current issue
that is left unaddressed.

Regards,

K. Y 
> 
> --
> 			Gleb.

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Gleb Natapov]

On Fri, Sep 13, 2013 at 02:28:35PM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Gleb Natapov [mailto:gleb@redhat.com]
> > Sent: Friday, September 13, 2013 2:55 AM
> > To: KY Srinivasan
> > Cc: H. Peter Anvin; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> > kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> > apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> > JBeulich@suse.com; bp@alien8.de
> > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> > from the hypervisor
> > 
> > On Fri, Sep 13, 2013 at 01:43:09AM +0000, KY Srinivasan wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: H. Peter Anvin [mailto:hpa@zytor.com]
> > > > Sent: Thursday, September 12, 2013 5:28 PM
> > > > To: KY Srinivasan
> > > > Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-
> > kernel@vger.kernel.org;
> > > > devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> > > > jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com;
> > bp@alien8.de
> > > > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> > > > from the hypervisor
> > > >
> > > > On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> > > > >
> > > > > Peter,
> > > > >
> > > > > Let me know if you want me to address any additional issues in this patch.
> > > > >
> > > >
> > > > Please address Jan and Gleb's feedback.
> > >
> > > Gleb's feedback was a question and I answered that as I did Jan's feedback as
> > well.
> > > Gleb, Jan, please let me know if there is something else you want addressed
> > here.
> > >
> > No, I am just interesting to know some details about the interface since
> > I cannot find it documented in Hyper-V spec.
> 
> Thanks Gleb. Here is the link for the latest Hyper-V specification:
> http://www.microsoft.com/en-us/download/details.aspx?id=39289
> 
> This spec talks about how migration is handled with regards to TSC.
> 
All I can see is "15.4.3 Partition Reference TSC Mechanism". I see
nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
a partition needs AccessFrequencyMsrs privilege, may be partition that
cab be migrated does not have this privilege?

--
			Gleb.

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: Gleb Natapov [mailto:gleb@redhat.com]
> Sent: Tuesday, September 17, 2013 6:59 AM
> To: KY Srinivasan
> Cc: H. Peter Anvin; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On Fri, Sep 13, 2013 at 02:28:35PM +0000, KY Srinivasan wrote:
> >
> >
> > > -----Original Message-----
> > > From: Gleb Natapov [mailto:gleb@redhat.com]
> > > Sent: Friday, September 13, 2013 2:55 AM
> > > To: KY Srinivasan
> > > Cc: H. Peter Anvin; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> > > kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> > > apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> > > JBeulich@suse.com; bp@alien8.de
> > > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> > > from the hypervisor
> > >
> > > On Fri, Sep 13, 2013 at 01:43:09AM +0000, KY Srinivasan wrote:
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: H. Peter Anvin [mailto:hpa@zytor.com]
> > > > > Sent: Thursday, September 12, 2013 5:28 PM
> > > > > To: KY Srinivasan
> > > > > Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-
> > > kernel@vger.kernel.org;
> > > > > devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> > > > > jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com;
> > > bp@alien8.de
> > > > > Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer
> frequency
> > > > > from the hypervisor
> > > > >
> > > > > On 09/12/2013 05:06 PM, KY Srinivasan wrote:
> > > > > >
> > > > > > Peter,
> > > > > >
> > > > > > Let me know if you want me to address any additional issues in this
> patch.
> > > > > >
> > > > >
> > > > > Please address Jan and Gleb's feedback.
> > > >
> > > > Gleb's feedback was a question and I answered that as I did Jan's feedback
> as
> > > well.
> > > > Gleb, Jan, please let me know if there is something else you want
> addressed
> > > here.
> > > >
> > > No, I am just interesting to know some details about the interface since
> > > I cannot find it documented in Hyper-V spec.
> >
> > Thanks Gleb. Here is the link for the latest Hyper-V specification:
> > http://www.microsoft.com/en-us/download/details.aspx?id=39289
> >
> > This spec talks about how migration is handled with regards to TSC.
> >
> All I can see is "15.4.3 Partition Reference TSC Mechanism". I see
> nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
> a partition needs AccessFrequencyMsrs privilege, may be partition that
> cab be migrated does not have this privilege?

If you use the MSR to read the TSC frequency, then indeed when you migrate then there
is no guarantee that the TSC frequency won't change when you migrate. The approach
described in section 15.4.3 is the preferred approach that can accommodate migration.

Regards,

K. Y 
> 
> --
> 			Gleb.

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Gleb Natapov]

On Tue, Sep 17, 2013 at 07:53:36PM +0000, KY Srinivasan wrote:
> > > Thanks Gleb. Here is the link for the latest Hyper-V specification:
> > > http://www.microsoft.com/en-us/download/details.aspx?id=39289
> > >
> > > This spec talks about how migration is handled with regards to TSC.
> > >
> > All I can see is "15.4.3 Partition Reference TSC Mechanism". I see
> > nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
> > a partition needs AccessFrequencyMsrs privilege, may be partition that
> > cab be migrated does not have this privilege?
> 
> If you use the MSR to read the TSC frequency, then indeed when you migrate then there
> is no guarantee that the TSC frequency won't change when you migrate. The approach
> described in section 15.4.3 is the preferred approach that can accommodate migration.
> 
Thanks.

--
			Gleb.

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: Gleb Natapov [mailto:gleb@redhat.com]
> Sent: Tuesday, September 17, 2013 10:44 PM
> To: KY Srinivasan
> Cc: H. Peter Anvin; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On Tue, Sep 17, 2013 at 07:53:36PM +0000, KY Srinivasan wrote:
> > > > Thanks Gleb. Here is the link for the latest Hyper-V specification:
> > > > http://www.microsoft.com/en-us/download/details.aspx?id=39289
> > > >
> > > > This spec talks about how migration is handled with regards to TSC.
> > > >
> > > All I can see is "15.4.3 Partition Reference TSC Mechanism". I see
> > > nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
> > > a partition needs AccessFrequencyMsrs privilege, may be partition that
> > > cab be migrated does not have this privilege?
> >
> > If you use the MSR to read the TSC frequency, then indeed when you migrate
> then there
> > is no guarantee that the TSC frequency won't change when you migrate. The
> approach
> > described in section 15.4.3 is the preferred approach that can accommodate
> migration.
> >
> Thanks.

Peter,
Please let me know if there are other issues I need to address here. Now that Dmitry has queued up the
Hyper-V keyboard driver, with this patch we can fully support Linux on our uefi firmware.

Regards,

K. Y 

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[H. Peter Anvin]

On 09/23/2013 06:02 AM, KY Srinivasan wrote:
> 
> Peter,
> Please let me know if there are other issues I need to address here. Now that Dmitry has queued up the
> Hyper-V keyboard driver, with this patch we can fully support Linux on our uefi firmware.
> 

I just got back from Plumber's -- this is on my short list of things to
look at.  If you haven't heard anything by Wednesday, ping me.

	-hpa

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: H. Peter Anvin [mailto:hpa@zytor.com]
> Sent: Monday, September 23, 2013 8:50 AM
> To: KY Srinivasan
> Cc: Gleb Natapov; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> JBeulich@suse.com; bp@alien8.de; dmitry.torokhov@gmail.com
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On 09/23/2013 06:02 AM, KY Srinivasan wrote:
> >
> > Peter,
> > Please let me know if there are other issues I need to address here. Now that
> Dmitry has queued up the
> > Hyper-V keyboard driver, with this patch we can fully support Linux on our uefi
> firmware.
> >
> 
> I just got back from Plumber's -- this is on my short list of things to
> look at.  If you haven't heard anything by Wednesday, ping me.

Thank you.

K. Y

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Olaf Hering]

On Tue, Sep 03, K. Y. Srinivasan wrote:

> Hyper-V supports a mechanism for retrieving the local APIC 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.

> +	if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
> +		/*
> +		 * Get the APIC frequency.
> +		 */
> +		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
> +		hv_lapic_frequency /= HZ;

This leads to build errors on 32bit:

linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to `__udivdi3'

Up to now I have only tested on 64bit, sorry for that.


Olaf

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

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> -----Original Message-----
> From: Olaf Hering [mailto:olaf@aepfle.de]
> Sent: Friday, September 27, 2013 8:10 AM
> To: KY Srinivasan
> Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; apw@canonical.com; jasowang@redhat.com;
> tglx@linutronix.de; hpa@zytor.com; JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On Tue, Sep 03, K. Y. Srinivasan wrote:
> 
> > Hyper-V supports a mechanism for retrieving the local APIC 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.
> 
> > +	if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
> > +		/*
> > +		 * Get the APIC frequency.
> > +		 */
> > +		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
> > +		hv_lapic_frequency /= HZ;
> 
> This leads to build errors on 32bit:
> 
> linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to
> `__udivdi3'
> 
> Up to now I have only tested on 64bit, sorry for that.

Thanks Olaf. I am travelling currently; I will fix it when I get back (early next week).

K. Y
> 
> 
> Olaf
ÿôèº{.nÇ+‰·Ÿ®‰­†+%ŠËÿ±éݶ\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dʇڙë,j\a­¢f£¢·hšïêÿ‘êçz_è®\x03(­éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨è­Ú&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[Olaf Hering]

On Fri, Sep 27, KY Srinivasan wrote:

> > This leads to build errors on 32bit:
> > 
> > linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to
> > `__udivdi3'
> > 
> > Up to now I have only tested on 64bit, sorry for that.
> 
> Thanks Olaf. I am travelling currently; I will fix it when I get back (early next week).

This change seems to fix it:

-+              hv_lapic_frequency /= HZ;
++              div_u64(hv_lapic_frequency, HZ);

Olaf

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

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> -----Original Message-----
> From: Olaf Hering [mailto:olaf@aepfle.de]
> Sent: Friday, September 27, 2013 8:33 AM
> To: KY Srinivasan
> Cc: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; apw@canonical.com; jasowang@redhat.com;
> tglx@linutronix.de; hpa@zytor.com; JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On Fri, Sep 27, KY Srinivasan wrote:
> 
> > > This leads to build errors on 32bit:
> > >
> > > linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to
> > > `__udivdi3'
> > >
> > > Up to now I have only tested on 64bit, sorry for that.
> >
> > Thanks Olaf. I am travelling currently; I will fix it when I get back (early next
> week).
> 
> This change seems to fix it:
> 
> -+              hv_lapic_frequency /= HZ;
> ++              div_u64(hv_lapic_frequency, HZ);

Thanks Olaf. Could you submit the patch.

Regards,

K. Y
ÿôèº{.nÇ+‰·Ÿ®‰­†+%ŠËÿ±éݶ\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dʇڙë,j\a­¢f£¢·hšïêÿ‘êçz_è®\x03(­éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨è­Ú&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

> -----Original Message-----
> From: H. Peter Anvin [mailto:hpa@zytor.com]
> Sent: Monday, September 23, 2013 8:50 AM
> To: KY Srinivasan
> Cc: Gleb Natapov; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; jasowang@redhat.com; tglx@linutronix.de;
> JBeulich@suse.com; bp@alien8.de; dmitry.torokhov@gmail.com
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On 09/23/2013 06:02 AM, KY Srinivasan wrote:
> >
> > Peter,
> > Please let me know if there are other issues I need to address here. Now that
> Dmitry has queued up the
> > Hyper-V keyboard driver, with this patch we can fully support Linux on our uefi
> firmware.
> >
> 
> I just got back from Plumber's -- this is on my short list of things to
> look at.  If you haven't heard anything by Wednesday, ping me.

Ping.

K. Y
> 
> 	-hpa
> 

Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[H. Peter Anvin]

On 09/27/2013 08:35 AM, KY Srinivasan wrote:
> 
> Thanks Olaf. Could you submit the patch.
> 

Haven't heard anything from Olaf... could you fold in the fix and resumbit?

	-hpa

RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

[KY Srinivasan]

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> -----Original Message-----
> From: H. Peter Anvin [mailto:hpa@zytor.com]
> Sent: Wednesday, October 09, 2013 3:50 PM
> To: KY Srinivasan
> Cc: Olaf Hering; x86@kernel.org; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; apw@canonical.com;
> jasowang@redhat.com; tglx@linutronix.de; JBeulich@suse.com; bp@alien8.de
> Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
> from the hypervisor
> 
> On 09/27/2013 08:35 AM, KY Srinivasan wrote:
> >
> > Thanks Olaf. Could you submit the patch.
> >
> 
> Haven't heard anything from Olaf... could you fold in the fix and resumbit?

I think Olaf sent the updated patch out; I will dig up the email and resend it.

Regards,

K. Y
> 
> 	-hpa
> 

ÿôèº{.nÇ+‰·Ÿ®‰­†+%ŠËÿ±éݶ\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dʇڙë,j\a­¢f£¢·hšïêÿ‘êçz_è®\x03(­éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨è­Ú&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥