Re: [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
Reviewed-by: Boqun Feng
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
>
Re: [PATCH 08/10] clocksource/drivers/hyper-v: Handle sched_clock differences inline
On Thu, Feb 04, 2021 at 04:28:38PM +, Michael Kelley wrote: > From: Wei Liu Sent: Monday, February 1, 2021 10:55 AM > > > > On Wed, Jan 27, 2021 at 12:23:43PM -0800, Michael Kelley wrote: > > [...] > > > +/* > > > + * 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) > > > > sched_clock_register is not trivial. Having __always_inline here is > > going to make the compiled object bloated. > > > > Given this is a static function, I don't think we need to specify any > > inline keyword. The compiler should be able to determine whether this > > function should be inlined all by itself. > > > > Wei. > > There was an explicit request from Peter Zijlstra and Thomas Gleixner > to force it inline. See https://lore.kernel.org/patchwork/patch/1283635/ and > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/x86/include/asm/mshyperv.h?id=b9d8cf2eb3ceecdee3434b87763492aee9e28845 Oh. noinstr. I failed to notice the comment. Sorry for the noise. Wei.
RE: [PATCH 08/10] clocksource/drivers/hyper-v: Handle sched_clock differences inline
From: Wei Liu Sent: Monday, February 1, 2021 10:55 AM
>
> On Wed, Jan 27, 2021 at 12:23:43PM -0800, Michael Kelley wrote:
> [...]
> > +/*
> > + * 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)
>
> sched_clock_register is not trivial. Having __always_inline here is
> going to make the compiled object bloated.
>
> Given this is a static function, I don't think we need to specify any
> inline keyword. The compiler should be able to determine whether this
> function should be inlined all by itself.
>
> Wei.
There was an explicit request from Peter Zijlstra and Thomas Gleixner
to force it inline. See https://lore.kernel.org/patchwork/patch/1283635/ and
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/x86/include/asm/mshyperv.h?id=b9d8cf2eb3ceecdee3434b87763492aee9e28845
Michael
>
> > +{
> > +#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
> >
Re: [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:
[...]
> +/*
> + * 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)
sched_clock_register is not trivial. Having __always_inline here is
going to make the compiled object bloated.
Given this is a static function, I don't think we need to specify any
inline keyword. The compiler should be able to determine whether this
function should be inlined all by itself.
Wei.
> +{
> +#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
>
[PATCH 08/10] clocksource/drivers/hyper-v: Handle sched_clock differences inline
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
---
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
