linux.git/arch/powerpc/kernel/time.c, branch v5.10.258 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git powerpc/kcsan: Exclude udelay to prevent recursive instrumentation 2023-03-17T07:45:14+00:00 Rohan McLure rmclure@linux.ibm.com 2023-02-06T02:17:58+00:00 9a61a3a6ec660915b641dacc6ac40bb52cc9e06b [ Upstream commit 2a7ce82dc46c591c9244057d89a6591c9639b9b9 ] In order for KCSAN to increase its likelihood of observing a data race, it sets a watchpoint on memory accesses and stalls, allowing for detection of conflicting accesses by other kernel threads or interrupts. Stalls are implemented by injecting a call to udelay in instrumented code. To prevent recursive instrumentation, exclude udelay from being instrumented. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20230206021801.105268-3-rmclure@linux.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 2a7ce82dc46c591c9244057d89a6591c9639b9b9 ]

In order for KCSAN to increase its likelihood of observing a data race,
it sets a watchpoint on memory accesses and stalls, allowing for
detection of conflicting accesses by other kernel threads or interrupts.

Stalls are implemented by injecting a call to udelay in instrumented code.
To prevent recursive instrumentation, exclude udelay from being instrumented.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230206021801.105268-3-rmclure@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/time: Enable sched clock for irqtime 2021-03-04T10:38:01+00:00 Pingfan Liu kernelfans@gmail.com 2020-10-22T06:51:19+00:00 99e7c8d157707f735c406f93d8a3811aa2c73151 [ Upstream commit b709e32ef570b8b91dfbcb63cffac4324c87799f ] When CONFIG_IRQ_TIME_ACCOUNTING and CONFIG_VIRT_CPU_ACCOUNTING_GEN, powerpc does not enable "sched_clock_irqtime" and can not utilize irq time accounting. Like x86, powerpc does not use the sched_clock_register() interface. So it needs an dedicated call to enable_sched_clock_irqtime() to enable irq time accounting. Fixes: 518470fe962e ("powerpc: Add HAVE_IRQ_TIME_ACCOUNTING") Signed-off-by: Pingfan Liu <kernelfans@gmail.com> [mpe: Add fixes tag] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1603349479-26185-1-git-send-email-kernelfans@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit b709e32ef570b8b91dfbcb63cffac4324c87799f ]

When CONFIG_IRQ_TIME_ACCOUNTING and CONFIG_VIRT_CPU_ACCOUNTING_GEN, powerpc
does not enable "sched_clock_irqtime" and can not utilize irq time
accounting.

Like x86, powerpc does not use the sched_clock_register() interface. So it
needs an dedicated call to enable_sched_clock_irqtime() to enable irq time
accounting.

Fixes: 518470fe962e ("powerpc: Add HAVE_IRQ_TIME_ACCOUNTING")
Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
[mpe: Add fixes tag]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1603349479-26185-1-git-send-email-kernelfans@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/64: irq replay remove decrementer overflow check 2021-01-06T13:56:54+00:00 Nicholas Piggin npiggin@gmail.com 2020-11-07T01:43:36+00:00 b1e155ccc882cd54ca613965df5653860438b67a [ Upstream commit 59d512e4374b2d8a6ad341475dc94c4a4bdec7d3 ] This is way to catch some cases of decrementer overflow, when the decrementer has underflowed an odd number of times, while MSR[EE] was disabled. With a typical small decrementer, a timer that fires when MSR[EE] is disabled will be "lost" if MSR[EE] remains disabled for between 4.3 and 8.6 seconds after the timer expires. In any case, the decrementer interrupt would be taken at 8.6 seconds and the timer would be found at that point. So this check is for catching extreme latency events, and it prevents those latencies from being a further few seconds long. It's not obvious this is a good tradeoff. This is already a watchdog magnitude event and that situation is not improved a significantly with this check. For large decrementers, it's useless. Therefore remove this check, which avoids a mftb when enabling hard disabled interrupts (e.g., when enabling after coming from hardware interrupt handlers). Perhaps more importantly, it also removes the clunky MSR[EE] vs PACA_IRQ_HARD_DIS incoherency in soft-interrupt replay which simplifies the code. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201107014336.2337337-1-npiggin@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 59d512e4374b2d8a6ad341475dc94c4a4bdec7d3 ]

This is way to catch some cases of decrementer overflow, when the
decrementer has underflowed an odd number of times, while MSR[EE] was
disabled.

With a typical small decrementer, a timer that fires when MSR[EE] is
disabled will be "lost" if MSR[EE] remains disabled for between 4.3 and
8.6 seconds after the timer expires. In any case, the decrementer
interrupt would be taken at 8.6 seconds and the timer would be found at
that point.

So this check is for catching extreme latency events, and it prevents
those latencies from being a further few seconds long.  It's not obvious
this is a good tradeoff. This is already a watchdog magnitude event and
that situation is not improved a significantly with this check. For
large decrementers, it's useless.

Therefore remove this check, which avoids a mftb when enabling hard
disabled interrupts (e.g., when enabling after coming from hardware
interrupt handlers). Perhaps more importantly, it also removes the
clunky MSR[EE] vs PACA_IRQ_HARD_DIS incoherency in soft-interrupt replay
which simplifies the code.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201107014336.2337337-1-npiggin@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/time: Avoid using get_tbl() and get_tbu() internally 2020-10-08T10:17:15+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2020-10-01T12:42:41+00:00 942e89115b588b4b5df86930b5302a5c07b820ba get_tbl() is confusing as it returns the content of TBL register on PPC32 but the concatenation of TBL and TBU on PPC64. Use mftb() instead. Do the same with get_tbu() for consistency allthough it's name is less confusing. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/41573406a4eab98838decaa91649086fef1e6119.1601556145.git.christophe.leroy@csgroup.eu 
get_tbl() is confusing as it returns the content of TBL register
on PPC32 but the concatenation of TBL and TBU on PPC64.

Use mftb() instead.

Do the same with get_tbu() for consistency allthough it's name
is less confusing.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/41573406a4eab98838decaa91649086fef1e6119.1601556145.git.christophe.leroy@csgroup.eu
powerpc: Remove get_tb_or_rtc() 2020-10-08T10:17:14+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2020-09-29T06:48:39+00:00 6601ec1c2ba929430f5585ce7f9d9960b0e0a01d 601 is gone, get_tb_or_rtc() is equivalent to get_tb(). Replace the former by the later. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/3e8a13ee83418630c753c30cb722ae682d5b2d39.1601362098.git.christophe.leroy@csgroup.eu 
601 is gone, get_tb_or_rtc() is equivalent to get_tb().

Replace the former by the later.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/3e8a13ee83418630c753c30cb722ae682d5b2d39.1601362098.git.christophe.leroy@csgroup.eu
powerpc: Remove __USE_RTC() 2020-10-08T10:17:14+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2020-09-29T06:48:38+00:00 a4c5a355422920bcbfe3fd1f01aead2d3a2a820c Now that PowerPC 601 is gone, __USE_RTC() is never true. Remove it. That also leads to removing get_rtc() and get_rtcl() Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/4757e1ed21fe1968c761ae081d1f3d790a9673f8.1601362098.git.christophe.leroy@csgroup.eu 
Now that PowerPC 601 is gone, __USE_RTC() is never true.

Remove it.

That also leads to removing get_rtc() and get_rtcl()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/4757e1ed21fe1968c761ae081d1f3d790a9673f8.1601362098.git.christophe.leroy@csgroup.eu
powerpc64: Break asm/percpu.h vs spinlock_types.h dependency 2020-07-10T10:00:01+00:00 Peter Zijlstra peterz@infradead.org 2020-05-29T20:41:01+00:00 d6bdceb6c2276276c0392b926ccd2e5991d5cb9a In order to use <asm/percpu.h> in lockdep.h, we need to make sure asm/percpu.h does not itself depend on lockdep. The below seems to make that so and builds powerpc64-defconfig + PROVE_LOCKING. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ingo Molnar <mingo@kernel.org> https://lkml.kernel.org/r/20200623083721.336906073@infradead.org 
In order to use <asm/percpu.h> in lockdep.h, we need to make sure
asm/percpu.h does not itself depend on lockdep.

The below seems to make that so and builds powerpc64-defconfig +
PROVE_LOCKING.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
https://lkml.kernel.org/r/20200623083721.336906073@infradead.org
Revert "powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled" 2020-04-03T05:55:34+00:00 Nicholas Piggin npiggin@gmail.com 2020-04-02T12:04:01+00:00 abc3fce76adbdfa8f87272c784b388cd20b46049 This reverts commit ebb37cf3ffd39fdb6ec5b07111f8bb2f11d92c5f. That commit does not play well with soft-masked irq state manipulations in idle, interrupt replay, and possibly others due to tracing code sometimes using irq_work_queue (e.g., in trace_hardirqs_on()). That can cause PACA_IRQ_DEC to become set when it is not expected, and be ignored or cleared or cause warnings. The net result seems to be missing an irq_work until the next timer interrupt in the worst case which is usually not going to be noticed, however it could be a long time if the tick is disabled, which is against the spirit of irq_work and might cause real problems. The idea is still solid, but it would need more work. It's not really clear if it would be worth added complexity, so revert this for now (not a straight revert, but replace with a comment explaining why we might see interrupts happening, and gives git blame something to find). Fixes: ebb37cf3ffd3 ("powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled") Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200402120401.1115883-1-npiggin@gmail.com 
This reverts commit ebb37cf3ffd39fdb6ec5b07111f8bb2f11d92c5f.

That commit does not play well with soft-masked irq state
manipulations in idle, interrupt replay, and possibly others due to
tracing code sometimes using irq_work_queue (e.g., in
trace_hardirqs_on()). That can cause PACA_IRQ_DEC to become set when
it is not expected, and be ignored or cleared or cause warnings.

The net result seems to be missing an irq_work until the next timer
interrupt in the worst case which is usually not going to be noticed,
however it could be a long time if the tick is disabled, which is
against the spirit of irq_work and might cause real problems.

The idea is still solid, but it would need more work. It's not really
clear if it would be worth added complexity, so revert this for
now (not a straight revert, but replace with a comment explaining why
we might see interrupts happening, and gives git blame something to
find).

Fixes: ebb37cf3ffd3 ("powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200402120401.1115883-1-npiggin@gmail.com
powerpc/time: Replace <linux/clk-provider.h> by <linux/of_clk.h> 2020-04-03T05:17:22+00:00 Geert Uytterhoeven geert+renesas@glider.be 2020-02-13T08:38:04+00:00 60083063b755e29685902609e024ecd0c4a1a7d9 The PowerPC time code is not a clock provider, and just needs to call of_clk_init(). Hence it can include <linux/of_clk.h> instead of <linux/clk-provider.h>. Remove the #ifdef protecting the of_clk_init() call, as a stub is available for the !CONFIG_COMMON_CLK case. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Stephen Boyd <sboyd@kernel.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200213083804.24315-1-geert+renesas@glider.be 
The PowerPC time code is not a clock provider, and just needs to call
of_clk_init().

Hence it can include <linux/of_clk.h> instead of <linux/clk-provider.h>.

Remove the #ifdef protecting the of_clk_init() call, as a stub is
available for the !CONFIG_COMMON_CLK case.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200213083804.24315-1-geert+renesas@glider.be
powerpc/64s/exception: Avoid touching the stack in hdecrementer 2020-04-01T02:42:12+00:00 Nicholas Piggin npiggin@gmail.com 2020-02-25T17:35:25+00:00 2babd6ea43edacfc1577432baa187a7d212f3f4f The hdec interrupt handler is reported to sometimes fire in Linux if KVM leaves it pending after a guest exists. This is harmless, so there is a no-op handler for it. The interrupt handler currently uses the regular kernel stack. Change this to avoid touching the stack entirely. This should be the last place where the regular Linux stack can be accessed with asynchronous interrupts (including PMI) soft-masked. It might be possible to take advantage of this invariant, e.g., to context switch the kernel stack SLB entry without clearing MSR[EE]. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200225173541.1549955-17-npiggin@gmail.com 
The hdec interrupt handler is reported to sometimes fire in Linux if
KVM leaves it pending after a guest exists. This is harmless, so there
is a no-op handler for it.

The interrupt handler currently uses the regular kernel stack. Change
this to avoid touching the stack entirely.

This should be the last place where the regular Linux stack can be
accessed with asynchronous interrupts (including PMI) soft-masked.
It might be possible to take advantage of this invariant, e.g., to
context switch the kernel stack SLB entry without clearing MSR[EE].

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-17-npiggin@gmail.com