On 02/03/2021 02:29, Michael Kelley wrote:

From: Daniel Lezcano <redacted> Sent: Monday, March 1, 2021 4:22 AM

quoted

On 01/03/2021 02:15, Michael Kelley wrote:

quoted

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

quoted

Signed-off-by: Michael Kelley <redacted>
Reviewed-by: Boqun Feng <redacted>
---
 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)

quoted

 {
-	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.



-- 
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog