From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: Borislav Petkov <bp@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <john.stultz@linaro.org>,
linux-kernel@vger.kernel.org, Len Brown <lenb@kernel.org>,
Huang Rui <ray.huang@amd.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
kvm@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>,
Andy Lutomirski <luto@kernel.org>
Subject: [PATCH v3 16/18] x86/tsc: In read_tsc, use rdtsc_ordered() instead of get_cycles()
Date: Tue, 16 Jun 2015 17:36:04 -0700 [thread overview]
Message-ID: <c6ff621a053127a65b70f175443578db7a0711be.1434501121.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1434501120.git.luto@kernel.org>
In-Reply-To: <cover.1434501120.git.luto@kernel.org>
There are two logical changes here. First, this removes a check for
cpu_has_tsc. That check is unnecessary, as we don't register the
TSC as a clocksource on systems that have no TSC. Second, it adds a
barrier, thus preventing observable non-monotonicity.
I suspect that the missing barrier was never a problem in practice
because system calls themselves were heavy enough barriers to
prevent user code from observing time warps due to speculation.
(Without the corresponding barrier in the vDSO, however,
non-monotonicity is easy to detect.)
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/kernel/tsc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 21d6e04e3e82..451bade0d320 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -961,7 +961,7 @@ static struct clocksource clocksource_tsc;
*/
static cycle_t read_tsc(struct clocksource *cs)
{
- return (cycle_t)get_cycles();
+ return (cycle_t)rdtsc_ordered();
}
/*
--
2.4.2
next prev parent reply other threads:[~2015-06-17 0:38 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-17 0:35 [PATCH v3 00/18] x86/tsc: Clean up rdtsc helpers Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 01/18] x86/tsc: Inline native_read_tsc and remove __native_read_tsc Andy Lutomirski
2015-06-17 9:26 ` Borislav Petkov
2015-07-06 15:39 ` [tip:x86/asm] x86/asm/tsc: Inline native_read_tsc() and remove __native_read_tsc() tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 02/18] x86/msr/kvm: Remove vget_cycles() Andy Lutomirski
2015-06-17 9:42 ` Borislav Petkov
2015-06-17 13:34 ` Paolo Bonzini
2015-07-06 15:40 ` [tip:x86/asm] x86/asm/tsc, kvm: " tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 03/18] x86/tsc/paravirt: Remove the read_tsc and read_tscp paravirt hooks Andy Lutomirski
2015-06-17 9:56 ` Borislav Petkov
2015-06-17 9:56 ` Borislav Petkov
2015-06-19 15:32 ` Borislav Petkov
2015-06-19 15:32 ` Borislav Petkov
2015-06-19 16:14 ` Andy Lutomirski
2015-06-19 16:14 ` Andy Lutomirski
2015-06-19 17:13 ` Borislav Petkov
2015-06-19 17:13 ` Borislav Petkov
2015-07-06 15:40 ` [tip:x86/asm] x86/asm/tsc, x86/paravirt: Remove read_tsc() and read_tscp() " tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 04/18] x86/tsc: Replace rdtscll with native_read_tsc Andy Lutomirski
2015-06-17 10:03 ` Borislav Petkov
2015-07-06 15:40 ` [tip:x86/asm] x86/asm/tsc: Replace rdtscll() with native_read_tsc () tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 05/18] x86/tsc: Remove the rdtscp and rdtscpll macros Andy Lutomirski
2015-07-06 15:41 ` [tip:x86/asm] x86/asm/tsc: Remove the rdtscp() and rdtscpll() macros tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 06/18] x86/tsc: Use the full 64-bit tsc in tsc_delay Andy Lutomirski
2015-07-06 15:41 ` [tip:x86/asm] x86/asm/tsc: Use the full 64-bit TSC in delay_tsc() tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 07/18] x86/cpu/amd: Use the full 64-bit TSC to detect the 2.6.2 bug Andy Lutomirski
2015-07-06 15:41 ` [tip:x86/asm] x86/asm/tsc, " tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 08/18] baycom_epp: Replace rdtscl() with native_read_tsc() Andy Lutomirski
2015-06-17 0:49 ` Thomas Sailer
2015-06-20 13:54 ` walter harms
2015-06-20 13:54 ` walter harms
2015-06-20 14:14 ` Thomas Gleixner
2015-06-20 14:14 ` Thomas Gleixner
2015-06-20 14:26 ` Andy Lutomirski
2015-06-20 14:26 ` Andy Lutomirski
2015-06-20 16:30 ` Thomas Gleixner
2015-06-20 16:30 ` Thomas Gleixner
2015-07-06 15:42 ` [tip:x86/asm] x86/asm/tsc, drivers/net/hamradio/baycom_epp: " tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 09/18] staging/lirc_serial: Remove TSC-based timing Andy Lutomirski
2015-06-17 0:35 ` Andy Lutomirski
2015-07-06 15:42 ` [tip:x86/asm] x86/asm/tsc, " tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 10/18] input/joystick/analog: Switch from rdtscl() to native_read_tsc() Andy Lutomirski
2015-07-06 15:42 ` [tip:x86/asm] x86/asm/tsc, " tip-bot for Andy Lutomirski
2015-06-17 0:35 ` [PATCH v3 11/18] drivers/input/gameport: Replace rdtscl() with native_read_tsc() Andy Lutomirski
2015-07-06 15:43 ` [tip:x86/asm] x86/asm/tsc, drivers/input/gameport: Replace rdtscl () " tip-bot for Andy Lutomirski
2015-06-17 0:36 ` [PATCH v3 12/18] x86/tsc: Remove rdtscl() Andy Lutomirski
2015-07-06 15:43 ` [tip:x86/asm] x86/asm/tsc: " tip-bot for Andy Lutomirski
2015-06-17 0:36 ` [PATCH v3 13/18] x86/tsc: Rename native_read_tsc() to rdtsc() Andy Lutomirski
2015-06-24 21:38 ` Borislav Petkov
2015-07-06 15:43 ` [tip:x86/asm] x86/asm/tsc: " tip-bot for Andy Lutomirski
2015-06-17 0:36 ` [PATCH v3 14/18] x86: Add rdtsc_ordered() and use it in trivial call sites Andy Lutomirski
2015-07-06 15:44 ` [tip:x86/asm] x86/asm/tsc: " tip-bot for Andy Lutomirski
2015-08-21 7:45 ` [tip:x86/asm] x86/asm/tsc: Add rdtscll() merge helper tip-bot for Ingo Molnar
2015-06-17 0:36 ` [PATCH v3 15/18] x86/tsc: Use rdtsc_ordered() in check_tsc_warp() and drop extra barriers Andy Lutomirski
2015-07-06 15:44 ` [tip:x86/asm] x86/asm/tsc/sync: " tip-bot for Andy Lutomirski
2015-06-17 0:36 ` Andy Lutomirski [this message]
2015-07-06 15:44 ` [tip:x86/asm] x86/asm/tsc: Use rdtsc_ordered() in read_tsc() instead of get_cycles() tip-bot for Andy Lutomirski
2015-06-17 0:36 ` [PATCH v3 17/18] x86/kvm/tsc: Drop extra barrier and use rdtsc_ordered in kvmclock Andy Lutomirski
2015-06-17 7:47 ` Paolo Bonzini
2015-06-17 13:31 ` Paolo Bonzini
2015-06-20 21:50 ` Borislav Petkov
2015-06-20 21:50 ` Borislav Petkov
2015-07-06 15:45 ` [tip:x86/asm] x86/asm/tsc, x86/kvm: Drop open-coded barrier and use rdtsc_ordered() " tip-bot for Andy Lutomirski
2015-06-17 0:36 ` [PATCH v3 18/18] x86/tsc: Remove rdtsc_barrier() Andy Lutomirski
2015-07-06 15:45 ` [tip:x86/asm] x86/asm/tsc: " tip-bot for Andy Lutomirski
2015-06-17 11:11 ` [PATCH v3 00/18] x86/tsc: Clean up rdtsc helpers Borislav Petkov
2015-06-17 13:37 ` Paolo Bonzini
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