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

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Date:   Thu, 13 May 2021 09:32:46 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     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>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE_HVCLOCK on X86

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