Re: [PATCH v2 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline
On 02/03/2021 02:29, Michael Kelley wrote:
> From: Daniel Lezcano Sent: Monday, March 1, 2021
> 4:22 AM
>>
>> On 01/03/2021 02:15, 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.
>>
>> A suggestion below
>>
>>
>>> Signed-off-by: Michael Kelley
>>> Reviewed-by: Boqun Feng
>>> ---
>>> arch/x86/include/asm/mshyperv.h| 4
>>> drivers/clocksource/hyperv_timer.c | 10 --
>>> 2 files changed, 8 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/clocksource/hyperv_timer.c
>>> b/drivers/clocksource/hyperv_timer.c
>>> index c73c127..5e5e08aa 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)
>>
>> static __maybe_unused 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
>>
>> #ifdef VDSO_CLOCKMODE_HVCLOCK
>> .enable = hv_cs_enable,
>> .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
>> #else
>> .vdso_clock_mode = VDSO_CLOCKMODE_NONE,
>> #endif
>>
>
> Is there any particular benefit (that I might not be recognizing)
> to having the .enable function be NULL vs. a function that
> does nothing? I can see the handful of places where the
> .enable function is invoked, and there doesn't seem to be
> much difference.
>
> In any case, I have no problem with making the change in
> a v3 of the patch set.
It is just coding style, it allows to remove a #ifdef in the code.
--
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RE: [PATCH v2 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline
From: Daniel Lezcano Sent: Monday, March 1, 2021
4:22 AM
>
> On 01/03/2021 02:15, 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.
>
> A suggestion below
>
>
> > Signed-off-by: Michael Kelley
> > Reviewed-by: Boqun Feng
> > ---
> > arch/x86/include/asm/mshyperv.h| 4
> > drivers/clocksource/hyperv_timer.c | 10 --
> > 2 files changed, 8 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/clocksource/hyperv_timer.c
> > b/drivers/clocksource/hyperv_timer.c
> > index c73c127..5e5e08aa 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)
>
> static __maybe_unused 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
>
> #ifdef VDSO_CLOCKMODE_HVCLOCK
> .enable = hv_cs_enable,
> .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
> #else
> .vdso_clock_mode = VDSO_CLOCKMODE_NONE,
> #endif
>
Is there any particular benefit (that I might not be recognizing)
to having the .enable function be NULL vs. a function that
does nothing? I can see the handful of places where the
.enable function is invoked, and there doesn't seem to be
much difference.
In any case, I have no problem with making the change in
a v3 of the patch set.
Michael
Re: [PATCH v2 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline
On 01/03/2021 02:15, 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.
A suggestion below
> Signed-off-by: Michael Kelley
> Reviewed-by: Boqun Feng
> ---
> 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 c10dd1c..4f566db 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 c73c127..5e5e08aa 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)
static __maybe_unused 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
#ifdef VDSO_CLOCKMODE_HVCLOCK
.enable = hv_cs_enable,
.vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
#else
.vdso_clock_mode = VDSO_CLOCKMODE_NONE,
#endif
> };
>
> static u64 notrace read_hv_clock_msr(void)
> @@ -442,7 +449,6 @@ 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();
>
--
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