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SubjectRe: [PATCH 08/10] clocksource/drivers/hyper-v: Handle sched_clock differences inline
On Wed, Jan 27, 2021 at 12:23:43PM -0800, Michael Kelley wrote:
> While the Hyper-V Reference TSC code is architecture neutral, the
> pv_ops.time.sched_clock() function is implemented for x86/x64, but not
> for ARM64. Current code calls a utility function under arch/x86 (and
> coming, under arch/arm64) to handle the difference.
>
> Change this approach to handle the difference inline based on whether
> GENERIC_SCHED_CLOCK 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 <mikelley@microsoft.com>

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

Regards,
Boqun

> ---
> arch/x86/include/asm/mshyperv.h | 11 -----------
> drivers/clocksource/hyperv_timer.c | 21 +++++++++++++++++++++
> 2 files changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index ed9dc56..5ccbba8 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -29,17 +29,6 @@ static inline u64 hv_get_register(unsigned int reg)
>
> #define hv_get_raw_timer() rdtsc_ordered()
>
> -/*
> - * Reference to pv_ops must be inline so objtool
> - * detection of noinstr violations can work correctly.
> - */
> -static __always_inline void hv_setup_sched_clock(void *sched_clock)
> -{
> -#ifdef CONFIG_PARAVIRT
> - pv_ops.time.sched_clock = sched_clock;
> -#endif
> -}
> -
> void hyperv_vector_handler(struct pt_regs *regs);
>
> static inline void hv_enable_stimer0_percpu_irq(int irq) {}
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 9cee6db..a2bee50 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -423,6 +423,27 @@ static u64 notrace read_hv_sched_clock_msr(void)
> .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> };
>
> +/*
> + * Reference to pv_ops must be inline so objtool
> + * detection of noinstr violations can work correctly.
> + */
> +static __always_inline void hv_setup_sched_clock(void *sched_clock)
> +{
> +#ifdef CONFIG_GENERIC_SCHED_CLOCK
> + /*
> + * We're on an architecture with generic sched clock (not x86/x64).
> + * The Hyper-V sched clock read function returns nanoseconds, not
> + * the normal 100ns units of the Hyper-V synthetic clock.
> + */
> + sched_clock_register(sched_clock, 64, NSEC_PER_SEC);
> +#else
> +#ifdef CONFIG_PARAVIRT
> + /* We're on x86/x64 *and* using PV ops */
> + pv_ops.time.sched_clock = sched_clock;
> +#endif
> +#endif
> +}
> +
> static bool __init hv_init_tsc_clocksource(void)
> {
> u64 tsc_msr;
> --
> 1.8.3.1
>

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