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Subject[tip:x86/vdso] x86/vdso: Enforce 64bit clocksource
Commit-ID:  a51e996d48ac9fa0a1260a3822a14f3d570d3be7
Gitweb: https://git.kernel.org/tip/a51e996d48ac9fa0a1260a3822a14f3d570d3be7
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Mon, 17 Sep 2018 14:45:36 +0200
Committer: Thomas Gleixner <tglx@linutronix.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@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Rickard <matt@softrans.com.au>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: devel@linuxdriverproject.org
Cc: virtualization@lists.linux-foundation.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Juergen Gross <jgross@suse.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;
+ }
}
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