linux-kernel - Re: [PATCH] clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE

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Message-ID: <87tun766kv.ffs@nanos.tec.linutronix.de>
Date:   Wed, 12 May 2021 22:27:28 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-hyperv@...r.kernel.org
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Mohammed Gamal <mgamal@...hat.com>,
        Wei Liu <wei.liu@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE_HVCLOCK on X86

On Wed, May 12 2021 at 10:46, Vitaly Kuznetsov wrote:
> Mohammed reports (https://bugzilla.kernel.org/show_bug.cgi?id=213029)
> the commit e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO
> differences inline") broke vDSO on x86. The problem appears to be that
> VDSO_CLOCKMODE_HVCLOCK is an enum value in 'enum vdso_clock_mode' and
> '#ifdef VDSO_CLOCKMODE_HVCLOCK' branch evaluates to false (it is not
> a define). Replace it with CONFIG_X86 as it is the only arch which
> has this mode currently.
>
> Reported-by: Mohammed Gamal <mgamal@...hat.com>
> Fixes: e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline")
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  drivers/clocksource/hyperv_timer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 977fd05ac35f..e17421f5e47d 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -419,7 +419,7 @@ static void resume_hv_clock_tsc(struct clocksource *arg)
>  	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr);
>  }
>  
> -#ifdef VDSO_CLOCKMODE_HVCLOCK
> +#ifdef CONFIG_X86
>  static int hv_cs_enable(struct clocksource *cs)
>  {
>  	vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
> @@ -435,7 +435,7 @@ static struct clocksource hyperv_cs_tsc = {
>  	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
>  	.suspend= suspend_hv_clock_tsc,
>  	.resume	= resume_hv_clock_tsc,
> -#ifdef VDSO_CLOCKMODE_HVCLOCK
> +#ifdef CONFIG_X86
>  	.enable = hv_cs_enable,
>  	.vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
>  #else

That's lame as it needs to be patched differently once ARM64 gains
support. What about the below?

Thanks,

        tglx
---
--- a/arch/x86/include/asm/vdso/clocksource.h
+++ b/arch/x86/include/asm/vdso/clocksource.h
@@ -7,4 +7,6 @@
 	VDSO_CLOCKMODE_PVCLOCK,	\
 	VDSO_CLOCKMODE_HVCLOCK
 
+#define HAVE_VDSO_CLOCKMODE_HVCLOCK
+
 #endif /* __ASM_VDSO_CLOCKSOURCE_H */
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -419,7 +419,7 @@ static void resume_hv_clock_tsc(struct c
 	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr);
 }
 
-#ifdef VDSO_CLOCKMODE_HVCLOCK
+#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK
 static int hv_cs_enable(struct clocksource *cs)
 {
 	vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
@@ -435,7 +435,7 @@ static struct clocksource hyperv_cs_tsc
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 	.suspend= suspend_hv_clock_tsc,
 	.resume	= resume_hv_clock_tsc,
-#ifdef VDSO_CLOCKMODE_HVCLOCK
+#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK
 	.enable = hv_cs_enable,
 	.vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
 #else