Re: [PATCH 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline

[Boqun Feng]

On Wed, Jan 27, 2021 at 12:23:42PM -0800, Michael Kelley wrote:
> While the driver for the Hyper-V Reference TSC and STIMERs is architecture
> neutral, vDSO is implemented for x86/x64, but not for ARM64.  Current code
> calls into utility functions under arch/x86 (and coming, under arch/arm64)
> to handle the difference.
> 
> Change this approach to handle the difference inline based on whether
> VDSO_CLOCK_MODE_HVCLOCK is present.  The new approach removes code under
> arch/* since the difference is tied more to the specifics of the Linux
> implementation than to the architecture.
> 
> No functional change.
> 
> Signed-off-by: Michael Kelley 

Reviewed-by: Boqun Feng 

Regards,
Boqun

> ---
>  arch/x86/include/asm/mshyperv.h|  4 
>  drivers/clocksource/hyperv_timer.c | 10 --
>  2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 4d3e0c5..ed9dc56 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -27,10 +27,6 @@ static inline u64 hv_get_register(unsigned int reg)
>   return value;
>  }
>  
> -#define hv_set_clocksource_vdso(val) \
> - ((val).vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK)
> -#define hv_enable_vdso_clocksource() \
> - vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
>  #define hv_get_raw_timer() rdtsc_ordered()
>  
>  /*
> diff --git a/drivers/clocksource/hyperv_timer.c 
> b/drivers/clocksource/hyperv_timer.c
> index 9425308..9cee6db 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -372,7 +372,9 @@ static void resume_hv_clock_tsc(struct clocksource *arg)
>  
>  static int hv_cs_enable(struct clocksource *cs)
>  {
> - hv_enable_vdso_clocksource();
> +#ifdef VDSO_CLOCKMODE_HVCLOCK
> + vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
> +#endif
>   return 0;
>  }
>  
> @@ -385,6 +387,11 @@ static int hv_cs_enable(struct clocksource *cs)
>   .suspend= suspend_hv_clock_tsc,
>   .resume = resume_hv_clock_tsc,
>   .enable = hv_cs_enable,
> +#ifdef VDSO_CLOCKMODE_HVCLOCK
> + .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
> +#else
> + .vdso_clock_mode = VDSO_CLOCKMODE_NONE,
> +#endif
>  };
>  
>  static u64 notrace read_hv_clock_msr(void)
> @@ -439,7 +446,6 @@ static bool __init hv_init_tsc_clocksource(void)
>   tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
>   hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr);
>  
> - hv_set_clocksource_vdso(hyperv_cs_tsc);
>   clocksource_register_hz(_cs_tsc, NSEC_PER_SEC/100);
>  
>   hv_sched_clock_offset = hv_read_reference_counter();
> -- 
> 1.8.3.1
> 

[PATCH 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline

[Michael Kelley]

While the driver for the Hyper-V Reference TSC and STIMERs is architecture
neutral, vDSO is implemented for x86/x64, but not for ARM64.  Current code
calls into utility functions under arch/x86 (and coming, under arch/arm64)
to handle the difference.

Change this approach to handle the difference inline based on whether
VDSO_CLOCK_MODE_HVCLOCK is present.  The new approach removes code under
arch/* since the difference is tied more to the specifics of the Linux
implementation than to the architecture.

No functional change.

Signed-off-by: Michael Kelley 
---
 arch/x86/include/asm/mshyperv.h|  4 
 drivers/clocksource/hyperv_timer.c | 10 --
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 4d3e0c5..ed9dc56 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -27,10 +27,6 @@ static inline u64 hv_get_register(unsigned int reg)
return value;
 }
 
-#define hv_set_clocksource_vdso(val) \
-   ((val).vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK)
-#define hv_enable_vdso_clocksource() \
-   vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
 #define hv_get_raw_timer() rdtsc_ordered()
 
 /*
diff --git a/drivers/clocksource/hyperv_timer.c 
b/drivers/clocksource/hyperv_timer.c
index 9425308..9cee6db 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -372,7 +372,9 @@ static void resume_hv_clock_tsc(struct clocksource *arg)
 
 static int hv_cs_enable(struct clocksource *cs)
 {
-   hv_enable_vdso_clocksource();
+#ifdef VDSO_CLOCKMODE_HVCLOCK
+   vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
+#endif
return 0;
 }
 
@@ -385,6 +387,11 @@ static int hv_cs_enable(struct clocksource *cs)
.suspend= suspend_hv_clock_tsc,
.resume = resume_hv_clock_tsc,
.enable = hv_cs_enable,
+#ifdef VDSO_CLOCKMODE_HVCLOCK
+   .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
+#else
+   .vdso_clock_mode = VDSO_CLOCKMODE_NONE,
+#endif
 };
 
 static u64 notrace read_hv_clock_msr(void)
@@ -439,7 +446,6 @@ static bool __init hv_init_tsc_clocksource(void)
tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr);
 
-   hv_set_clocksource_vdso(hyperv_cs_tsc);
clocksource_register_hz(_cs_tsc, NSEC_PER_SEC/100);
 
hv_sched_clock_offset = hv_read_reference_counter();
-- 
1.8.3.1