[PATCH V2 0/2] clocksource/Hyper-V: Add Hyper-V specific sched clock

[PATCH V2 0/2] clocksource/Hyper-V: Add Hyper-V specific sched clock

[lantianyu1986]

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Hyper-V guests use the default native_sched_clock() in pv_ops.time.sched_clock
on x86. But native_sched_clock() directly uses the raw TSC value, which
can be discontinuous in a Hyper-V VM.   Add the generic hv_setup_sched_clock()
to set the sched clock function appropriately.  On x86, this sets
pv_ops.time.sched_clock to read the Hyper-V reference TSC value that is
scaled and adjusted to be continuous.

Also move the Hyper-V reference TSC initialization much earlier in the boot
process so no discontinuity is observed when pv_ops.time.sched_clock
calculates its offset.  This earlier initialization requires that the Hyper-V TSC
page be allocated statically instead of with vmalloc(), so fixup the references
to the TSC page and the method of getting its physical address.

Change since v1:
	- Update patch 1 commit log
	- Remove and operation of tsc page's va with PAGE_MASK
	in the read_hv_sched_clock_tsc().

Tianyu Lan (2):
  clocksource/Hyper-v: Allocate Hyper-V tsc page statically
  clocksource/Hyper-V:  Add Hyper-V specific sched clock function

 arch/x86/entry/vdso/vma.c          |  2 +-
 arch/x86/hyperv/hv_init.c          |  2 --
 arch/x86/kernel/cpu/mshyperv.c     |  8 ++++++++
 drivers/clocksource/hyperv_timer.c | 34 ++++++++++++++++------------------
 include/asm-generic/mshyperv.h     |  1 +
 5 files changed, 26 insertions(+), 21 deletions(-)

-- 
2.14.5

[PATCH V2 1/2] clocksource/Hyper-v: Allocate Hyper-V tsc page statically

[lantianyu1986]

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Prepare to add Hyper-V sched clock callback and move Hyper-V
Reference TSC initialization much earlier in the boot process.  Earlier
initialization is needed so that it happens while the timestamp value
is still 0 and no discontinuity in the timestamp will occur when
pv_ops.time.sched_clock calculates its offset.  The earlier
initialization requires that the Hyper-V TSC page be allocated
statically instead of with vmalloc(), so fixup the references
to the TSC page and the method of getting its physical address.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
    Change since v1:
           - Update commit log
           - Remove and operation of tsc page's va with PAGE_MASK

 arch/x86/entry/vdso/vma.c          |  2 +-
 drivers/clocksource/hyperv_timer.c | 12 ++++--------
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 349a61d8bf34..f5937742b290 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -122,7 +122,7 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 
 		if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
 			return vmf_insert_pfn(vma, vmf->address,
-					vmalloc_to_pfn(tsc_pg));
+					virt_to_phys(tsc_pg) >> PAGE_SHIFT);
 	}
 
 	return VM_FAULT_SIGBUS;
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index ba2c79e6a0ee..432aa331df04 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -214,17 +214,17 @@ EXPORT_SYMBOL_GPL(hyperv_cs);
 
 #ifdef CONFIG_HYPERV_TSCPAGE
 
-static struct ms_hyperv_tsc_page *tsc_pg;
+static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
 
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
-	return tsc_pg;
+	return &tsc_pg;
 }
 EXPORT_SYMBOL_GPL(hv_get_tsc_page);
 
 static u64 notrace read_hv_sched_clock_tsc(void)
 {
-	u64 current_tick = hv_read_tsc_page(tsc_pg);
+	u64 current_tick = hv_read_tsc_page(&tsc_pg);
 
 	if (current_tick == U64_MAX)
 		hv_get_time_ref_count(current_tick);
@@ -280,12 +280,8 @@ static bool __init hv_init_tsc_clocksource(void)
 	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
 		return false;
 
-	tsc_pg = vmalloc(PAGE_SIZE);
-	if (!tsc_pg)
-		return false;
-
 	hyperv_cs = &hyperv_cs_tsc;
-	phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
+	phys_addr = virt_to_phys(&tsc_pg);
 
 	/*
 	 * The Hyper-V TLFS specifies to preserve the value of reserved
-- 
2.14.5

[PATCH V2 2/2] clocksource/Hyper-V: Add Hyper-V specific sched clock function

[lantianyu1986]

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Hyper-V guests use the default native_sched_clock() in pv_ops.time.sched_clock
on x86.  But native_sched_clock() directly uses the raw TSC value, which
can be discontinuous in a Hyper-V VM. Add the generic hv_setup_sched_clock()
to set the sched clock function appropriately. On x86, this sets pv_ops.time.
sched_clock to read the Hyper-V reference TSC value that is scaled and adjusted
to be continuous.

Also move the Hyper-V reference TSC initialization much earlier in the boot
process so no discontinuity is observed when pv_ops.time.sched_clock
calculates its offset.

Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
 arch/x86/hyperv/hv_init.c          |  2 --
 arch/x86/kernel/cpu/mshyperv.c     |  8 ++++++++
 drivers/clocksource/hyperv_timer.c | 22 ++++++++++++----------
 include/asm-generic/mshyperv.h     |  1 +
 4 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 0d258688c8cf..866dfb3dca48 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -301,8 +301,6 @@ void __init hyperv_init(void)
 
 	x86_init.pci.arch_init = hv_pci_init;
 
-	/* Register Hyper-V specific clocksource */
-	hv_init_clocksource();
 	return;
 
 remove_cpuhp_state:
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 062f77279ce3..53afd33990eb 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -29,6 +29,7 @@
 #include <asm/timer.h>
 #include <asm/reboot.h>
 #include <asm/nmi.h>
+#include <clocksource/hyperv_timer.h>
 
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -338,9 +339,16 @@ static void __init ms_hyperv_init_platform(void)
 		x2apic_phys = 1;
 # endif
 
+	/* Register Hyper-V specific clocksource */
+	hv_init_clocksource();
 #endif
 }
 
+void hv_setup_sched_clock(void *sched_clock)
+{
+	pv_ops.time.sched_clock = sched_clock;
+}
+
 const __initconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
 	.name			= "Microsoft Hyper-V",
 	.detect			= ms_hyperv_platform,
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 432aa331df04..dad8af198e20 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -215,6 +215,7 @@ EXPORT_SYMBOL_GPL(hyperv_cs);
 #ifdef CONFIG_HYPERV_TSCPAGE
 
 static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
+static u64 hv_sched_clock_offset __ro_after_init;
 
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
@@ -222,7 +223,7 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 }
 EXPORT_SYMBOL_GPL(hv_get_tsc_page);
 
-static u64 notrace read_hv_sched_clock_tsc(void)
+static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
 {
 	u64 current_tick = hv_read_tsc_page(&tsc_pg);
 
@@ -232,9 +233,9 @@ static u64 notrace read_hv_sched_clock_tsc(void)
 	return current_tick;
 }
 
-static u64 read_hv_clock_tsc(struct clocksource *arg)
+static u64 read_hv_sched_clock_tsc(void)
 {
-	return read_hv_sched_clock_tsc();
+	return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
 }
 
 static struct clocksource hyperv_cs_tsc = {
@@ -246,7 +247,7 @@ static struct clocksource hyperv_cs_tsc = {
 };
 #endif
 
-static u64 notrace read_hv_sched_clock_msr(void)
+static u64 notrace read_hv_clock_msr(struct clocksource *arg)
 {
 	u64 current_tick;
 	/*
@@ -258,9 +259,9 @@ static u64 notrace read_hv_sched_clock_msr(void)
 	return current_tick;
 }
 
-static u64 read_hv_clock_msr(struct clocksource *arg)
+static u64 read_hv_sched_clock_msr(void)
 {
-	return read_hv_sched_clock_msr();
+	return read_hv_clock_msr(NULL) - hv_sched_clock_offset;
 }
 
 static struct clocksource hyperv_cs_msr = {
@@ -298,8 +299,9 @@ static bool __init hv_init_tsc_clocksource(void)
 	hv_set_clocksource_vdso(hyperv_cs_tsc);
 	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
 
-	/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
-	sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
+	hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
+	hv_setup_sched_clock(read_hv_sched_clock_tsc);
+
 	return true;
 }
 #else
@@ -329,7 +331,7 @@ void __init hv_init_clocksource(void)
 	hyperv_cs = &hyperv_cs_msr;
 	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
 
-	/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
-	sched_clock_register(read_hv_sched_clock_msr, 64, HV_CLOCK_HZ);
+	hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
+	hv_setup_sched_clock(read_hv_sched_clock_msr);
 }
 EXPORT_SYMBOL_GPL(hv_init_clocksource);
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 0becb7d9704d..18d8e2d8210f 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -167,6 +167,7 @@ void hyperv_report_panic(struct pt_regs *regs, long err);
 void hyperv_report_panic_msg(phys_addr_t pa, size_t size);
 bool hv_is_hyperv_initialized(void);
 void hyperv_cleanup(void);
+void hv_setup_sched_clock(void *sched_clock);
 #else /* CONFIG_HYPERV */
 static inline bool hv_is_hyperv_initialized(void) { return false; }
 static inline void hyperv_cleanup(void) {}
-- 
2.14.5

Re: [PATCH V2 1/2] clocksource/Hyper-v: Allocate Hyper-V tsc page statically

[Daniel Lezcano]

On 14/08/2019 14:32, lantianyu1986@gmail.com wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Prepare to add Hyper-V sched clock callback and move Hyper-V
> Reference TSC initialization much earlier in the boot process.  Earlier
> initialization is needed so that it happens while the timestamp value
> is still 0 and no discontinuity in the timestamp will occur when
> pv_ops.time.sched_clock calculates its offset.  The earlier
> initialization requires that the Hyper-V TSC page be allocated
> statically instead of with vmalloc(), so fixup the references
> to the TSC page and the method of getting its physical address.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

> ---
>     Change since v1:
>            - Update commit log
>            - Remove and operation of tsc page's va with PAGE_MASK
> 
>  arch/x86/entry/vdso/vma.c          |  2 +-
>  drivers/clocksource/hyperv_timer.c | 12 ++++--------
>  2 files changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index 349a61d8bf34..f5937742b290 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -122,7 +122,7 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
>  
>  		if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
>  			return vmf_insert_pfn(vma, vmf->address,
> -					vmalloc_to_pfn(tsc_pg));
> +					virt_to_phys(tsc_pg) >> PAGE_SHIFT);
>  	}
>  
>  	return VM_FAULT_SIGBUS;
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index ba2c79e6a0ee..432aa331df04 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -214,17 +214,17 @@ EXPORT_SYMBOL_GPL(hyperv_cs);
>  
>  #ifdef CONFIG_HYPERV_TSCPAGE
>  
> -static struct ms_hyperv_tsc_page *tsc_pg;
> +static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
>  
>  struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
>  {
> -	return tsc_pg;
> +	return &tsc_pg;
>  }
>  EXPORT_SYMBOL_GPL(hv_get_tsc_page);
>  
>  static u64 notrace read_hv_sched_clock_tsc(void)
>  {
> -	u64 current_tick = hv_read_tsc_page(tsc_pg);
> +	u64 current_tick = hv_read_tsc_page(&tsc_pg);
>  
>  	if (current_tick == U64_MAX)
>  		hv_get_time_ref_count(current_tick);
> @@ -280,12 +280,8 @@ static bool __init hv_init_tsc_clocksource(void)
>  	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
>  		return false;
>  
> -	tsc_pg = vmalloc(PAGE_SIZE);
> -	if (!tsc_pg)
> -		return false;
> -
>  	hyperv_cs = &hyperv_cs_tsc;
> -	phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
> +	phys_addr = virt_to_phys(&tsc_pg);
>  
>  	/*
>  	 * The Hyper-V TLFS specifies to preserve the value of reserved
> 


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