From: Heiko Carstens <hca@linux.ibm.com>
To: Li Wang <liwang@redhat.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>
Cc: ltp@lists.linux.it, linux-kernel@vger.kernel.org,
linux-s390@vger.kernel.org
Subject: [PATCH 1/3] s390/vdso: fix tod clock steering
Date: Tue, 23 Mar 2021 22:58:17 +0100 [thread overview]
Message-ID: <20210323215819.4161164-2-hca@linux.ibm.com> (raw)
In-Reply-To: <20210323215819.4161164-1-hca@linux.ibm.com>
The s390 specific vdso function __arch_get_hw_counter() is supposed to
consider tod clock steering.
If a tod clock steering event happens and the tod clock is set to a
new value __arch_get_hw_counter() will not return the real tod clock
value but slowly drift it from the old delta until the returned value
finally matches the real tod clock value again.
When converting the assembler code to C it was forgotten to tell user
space in which direction the clock has to be adjusted.
Worst case is now that instead of drifting the clock slowly it will
jump into the opposite direction by a factor of two.
Fix this by simply providing the missing value to user space.
Fixes: 4bff8cb54502 ("s390: convert to GENERIC_VDSO")
Cc: <stable@vger.kernel.org> # 5.10
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
arch/s390/kernel/time.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 165da961f901..e37285a5101b 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -382,6 +382,7 @@ static void clock_sync_global(unsigned long delta)
tod_steering_delta);
tod_steering_end = now + (abs(tod_steering_delta) << 15);
vdso_data->arch_data.tod_steering_end = tod_steering_end;
+ vdso_data->arch_data.tod_steering_delta = tod_steering_delta;
/* Update LPAR offset. */
if (ptff_query(PTFF_QTO) && ptff(&qto, sizeof(qto), PTFF_QTO) == 0)
--
2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Heiko Carstens <hca@linux.ibm.com>
To: ltp@lists.linux.it
Subject: [LTP] [PATCH 1/3] s390/vdso: fix tod clock steering
Date: Tue, 23 Mar 2021 22:58:17 +0100 [thread overview]
Message-ID: <20210323215819.4161164-2-hca@linux.ibm.com> (raw)
In-Reply-To: <20210323215819.4161164-1-hca@linux.ibm.com>
The s390 specific vdso function __arch_get_hw_counter() is supposed to
consider tod clock steering.
If a tod clock steering event happens and the tod clock is set to a
new value __arch_get_hw_counter() will not return the real tod clock
value but slowly drift it from the old delta until the returned value
finally matches the real tod clock value again.
When converting the assembler code to C it was forgotten to tell user
space in which direction the clock has to be adjusted.
Worst case is now that instead of drifting the clock slowly it will
jump into the opposite direction by a factor of two.
Fix this by simply providing the missing value to user space.
Fixes: 4bff8cb54502 ("s390: convert to GENERIC_VDSO")
Cc: <stable@vger.kernel.org> # 5.10
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
arch/s390/kernel/time.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 165da961f901..e37285a5101b 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -382,6 +382,7 @@ static void clock_sync_global(unsigned long delta)
tod_steering_delta);
tod_steering_end = now + (abs(tod_steering_delta) << 15);
vdso_data->arch_data.tod_steering_end = tod_steering_end;
+ vdso_data->arch_data.tod_steering_delta = tod_steering_delta;
/* Update LPAR offset. */
if (ptff_query(PTFF_QTO) && ptff(&qto, sizeof(qto), PTFF_QTO) == 0)
--
2.25.1
next prev parent reply other threads:[~2021-03-23 21:59 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-23 6:21 [LTP] [s390x vDSO Bug?] clock_gettime(CLOCK_MONOTONIC_RAW, ...) gets abnormal ts value Li Wang
2021-03-23 7:11 ` Heiko Carstens
2021-03-23 7:11 ` [LTP] " Heiko Carstens
2021-03-23 13:48 ` Heiko Carstens
2021-03-23 13:48 ` [LTP] " Heiko Carstens
2021-03-23 21:58 ` [PATCH 0/3] s390 vdso fixes Heiko Carstens
2021-03-23 21:58 ` [LTP] " Heiko Carstens
2021-03-23 21:58 ` Heiko Carstens [this message]
2021-03-23 21:58 ` [LTP] [PATCH 1/3] s390/vdso: fix tod clock steering Heiko Carstens
2021-03-24 9:50 ` Heiko Carstens
2021-03-24 9:50 ` [LTP] " Heiko Carstens
2021-03-23 21:58 ` [PATCH 2/3] s390/vdso: fix arch_data access for __arch_get_hw_counter() Heiko Carstens
2021-03-23 21:58 ` [LTP] " Heiko Carstens
2021-03-24 5:53 ` Heiko Carstens
2021-03-24 5:53 ` [LTP] " Heiko Carstens
2021-03-23 21:58 ` [PATCH 3/3] lib/vdso: remove struct arch_vdso_data from vdso data struct Heiko Carstens
2021-03-23 21:58 ` [LTP] " Heiko Carstens
2021-03-25 17:55 ` Thomas Gleixner
2021-03-25 17:55 ` [LTP] " Thomas Gleixner
2021-03-25 17:57 ` Thomas Gleixner
2021-03-25 17:57 ` [LTP] " Thomas Gleixner
2021-03-25 8:56 ` [LTP] [PATCH 0/3] s390 vdso fixes Li Wang
2021-03-25 12:33 ` Heiko Carstens
2021-03-25 12:33 ` [LTP] " Heiko Carstens
2021-03-25 14:11 ` Li Wang
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