linux-kernel - RE: [PATCH v2] clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE

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Message-ID: <MWHPR21MB15932C5EC2FA75D50B268951D7519@MWHPR21MB1593.namprd21.prod.outlook.com>
Date:   Thu, 13 May 2021 13:29:12 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     vkuznets <vkuznets@...hat.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
CC:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Mohammed Gamal <mgamal@...hat.com>,
        Wei Liu <wei.liu@...nel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] clocksource/drivers/hyper-v: Re-enable
 VDSO_CLOCKMODE_HVCLOCK on X86

From: Vitaly Kuznetsov <vkuznets@...hat.com> Sent: Thursday, May 13, 2021 12:33 AM
> 
> 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). Use a dedicated HAVE_VDSO_CLOCKMODE_HVCLOCK define instead.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> 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>
> ---
>  arch/x86/include/asm/vdso/clocksource.h | 2 ++
>  drivers/clocksource/hyperv_timer.c      | 4 ++--
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vdso/clocksource.h
> b/arch/x86/include/asm/vdso/clocksource.h
> index 119ac8612d89..136e5e57cfe1 100644
> --- 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 */
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 977fd05ac35f..d6ece7bbce89 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 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
> --
> 2.31.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>