On 02/03/2021 02:29, Michael Kelley wrote:
> From: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> 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 <mikelley@xxxxxxxxxxxxx>
>>> Reviewed-by: Boqun Feng <boqun.feng@xxxxxxxxx>
>>> ---
>>> 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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