linux-kernel - [tip:x86/vdso] x86/vdso: Enforce 64bit clocksource

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Date:   Thu, 4 Oct 2018 14:05:06 -0700
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     luto@...nel.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de, john.stultz@...aro.org,
        pbonzini@...hat.com, arnd@...db.de, kys@...rosoft.com,
        mingo@...nel.org, fweimer@...hat.com, matt@...trans.com.au,
        vkuznets@...hat.com, sboyd@...nel.org, hpa@...or.com,
        jgross@...e.com
Subject: [tip:x86/vdso] x86/vdso: Enforce 64bit clocksource

Commit-ID:  a51e996d48ac9fa0a1260a3822a14f3d570d3be7
Gitweb:     https://git.kernel.org/tip/a51e996d48ac9fa0a1260a3822a14f3d570d3be7
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 17 Sep 2018 14:45:36 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 4 Oct 2018 23:00:25 +0200

x86/vdso: Enforce 64bit clocksource

All VDSO clock sources are TSC based and use CLOCKSOURCE_MASK(64). There is
no point in masking with all FF. Get rid of it and enforce the mask in the
sanity checker.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Andy Lutomirski <luto@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Matt Rickard <matt@...trans.com.au>
Cc: Stephen Boyd <sboyd@...nel.org>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Florian Weimer <fweimer@...hat.com>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: devel@...uxdriverproject.org
Cc: virtualization@...ts.linux-foundation.org
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Juergen Gross <jgross@...e.com>
Link: https://lkml.kernel.org/r/20180917130707.151963007@linutronix.de

---
 arch/x86/entry/vdso/vclock_gettime.c | 2 +-
 arch/x86/kernel/time.c               | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index e48ca3afa091..6a950854034f 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -201,7 +201,7 @@ notrace static inline u64 vgetsns(int *mode)
 #endif
 	else
 		return 0;
-	v = (cycles - gtod->cycle_last) & gtod->mask;
+	v = cycles - gtod->cycle_last;
 	return v * gtod->mult;
 }
 
diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index 1fa632e0829f..b23f5420b26a 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -120,4 +120,10 @@ void clocksource_arch_init(struct clocksource *cs)
 			cs->name, cs->archdata.vclock_mode);
 		cs->archdata.vclock_mode = VCLOCK_NONE;
 	}
+
+	if (cs->mask != CLOCKSOURCE_MASK(64)) {
+		pr_warn("clocksource %s registered with invalid mask %016llx. Disabling vclock.\n",
+			cs->name, cs->mask);
+		cs->archdata.vclock_mode = VCLOCK_NONE;
+	}
 }