* [PATCH v2] intel_idle: avoid tracing MSR writes while idling
@ 2022-08-24 23:42 Peter Shier
2022-08-25 8:41 ` Peter Zijlstra
2022-08-25 11:43 ` Rafael J. Wysocki
0 siblings, 2 replies; 3+ messages in thread
From: Peter Shier @ 2022-08-24 23:42 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Jacob Pan, Len Brown, Peter Zijlstra,
Michael Roth, Alexei Starovoitov, Josh Poimboeuf
Cc: linux-kernel, linux-pm, Peter Shier
With commit bf5835bcdb963 ("intel_idle: Disable IBRS during long idle"),
enabling wrmsr trace with CONFIG_LOCKDEP causes "suspicious
rcu_dereference_check() usage" warning because do_trace_write_msr does not
use trace_write_msr_rcuidle.
Change intel_idle_ibrs to use native_wrmsr to avoid tracing
Sample warning:
============================
WARNING: suspicious RCU usage
6.0.0-dbg-DEV #7 Tainted: G S O
-----------------------------
arch/x86/include/asm/msr-trace.h:48 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
RCU used illegally from extended quiescent state!
no locks held by swapper/59/0.
stack backtrace:
CPU: 59 PID: 0 Comm: swapper/59 Tainted: G S O 6.0.0-dbg-DEV #7
Call Trace:
dump_stack_lvl
dump_stack
lockdep_rcu_suspicious
trace_write_msr
do_trace_write_msr
intel_idle_ibrs
cpuidle_enter_state
cpuidle_enter
do_idle
cpu_startup_entry
start_secondary
secondary_startup_64_no_verify
Tested on skylake using:
echo "msr:write_msr" >/sys/kernel/debug/tracing/set_event
with and without patch.
Signed-off-by: Peter Shier <pshier@google.com>
---
v2:
- changed to avoid tracing
v1: https://lore.kernel.org/all/20220823234353.937002-1-pshier@google.com/
drivers/idle/intel_idle.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 3e101719689a..df129c73786f 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -187,12 +187,12 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev,
int ret;
if (smt_active)
- wrmsrl(MSR_IA32_SPEC_CTRL, 0);
+ native_wrmsr(MSR_IA32_SPEC_CTRL, 0);
ret = __intel_idle(dev, drv, index);
if (smt_active)
- wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl);
+ native_wrmsr(MSR_IA32_SPEC_CTRL, spec_ctrl);
return ret;
}
--
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v2] intel_idle: avoid tracing MSR writes while idling
2022-08-24 23:42 [PATCH v2] intel_idle: avoid tracing MSR writes while idling Peter Shier
@ 2022-08-25 8:41 ` Peter Zijlstra
2022-08-25 11:43 ` Rafael J. Wysocki
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2022-08-25 8:41 UTC (permalink / raw)
To: Peter Shier
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Jacob Pan, Len Brown, Michael Roth,
Alexei Starovoitov, Josh Poimboeuf, linux-kernel, linux-pm
On Wed, Aug 24, 2022 at 04:42:11PM -0700, Peter Shier wrote:
> With commit bf5835bcdb963 ("intel_idle: Disable IBRS during long idle"),
> enabling wrmsr trace with CONFIG_LOCKDEP causes "suspicious
> rcu_dereference_check() usage" warning because do_trace_write_msr does not
> use trace_write_msr_rcuidle.
>
> Change intel_idle_ibrs to use native_wrmsr to avoid tracing
>
> Signed-off-by: Peter Shier <pshier@google.com>
> ---
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> drivers/idle/intel_idle.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 3e101719689a..df129c73786f 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -187,12 +187,12 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev,
> int ret;
>
> if (smt_active)
> - wrmsrl(MSR_IA32_SPEC_CTRL, 0);
> + native_wrmsr(MSR_IA32_SPEC_CTRL, 0);
>
> ret = __intel_idle(dev, drv, index);
>
> if (smt_active)
> - wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl);
> + native_wrmsr(MSR_IA32_SPEC_CTRL, spec_ctrl);
>
> return ret;
> }
> --
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v2] intel_idle: avoid tracing MSR writes while idling
2022-08-24 23:42 [PATCH v2] intel_idle: avoid tracing MSR writes while idling Peter Shier
2022-08-25 8:41 ` Peter Zijlstra
@ 2022-08-25 11:43 ` Rafael J. Wysocki
1 sibling, 0 replies; 3+ messages in thread
From: Rafael J. Wysocki @ 2022-08-25 11:43 UTC (permalink / raw)
To: Peter Shier
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen,
the arch/x86 maintainers, H. Peter Anvin, Jacob Pan, Len Brown,
Peter Zijlstra, Michael Roth, Alexei Starovoitov, Josh Poimboeuf,
Linux Kernel Mailing List, Linux PM
On Thu, Aug 25, 2022 at 1:42 AM Peter Shier <pshier@google.com> wrote:
>
> With commit bf5835bcdb963 ("intel_idle: Disable IBRS during long idle"),
> enabling wrmsr trace with CONFIG_LOCKDEP causes "suspicious
> rcu_dereference_check() usage" warning because do_trace_write_msr does not
> use trace_write_msr_rcuidle.
>
> Change intel_idle_ibrs to use native_wrmsr to avoid tracing
>
> Sample warning:
> ============================
> WARNING: suspicious RCU usage
> 6.0.0-dbg-DEV #7 Tainted: G S O
> -----------------------------
> arch/x86/include/asm/msr-trace.h:48 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> RCU used illegally from extended quiescent state!
> no locks held by swapper/59/0.
>
> stack backtrace:
> CPU: 59 PID: 0 Comm: swapper/59 Tainted: G S O 6.0.0-dbg-DEV #7
> Call Trace:
> dump_stack_lvl
> dump_stack
> lockdep_rcu_suspicious
> trace_write_msr
> do_trace_write_msr
> intel_idle_ibrs
> cpuidle_enter_state
> cpuidle_enter
> do_idle
> cpu_startup_entry
> start_secondary
> secondary_startup_64_no_verify
>
> Tested on skylake using:
> echo "msr:write_msr" >/sys/kernel/debug/tracing/set_event
> with and without patch.
>
> Signed-off-by: Peter Shier <pshier@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> v2:
> - changed to avoid tracing
>
> v1: https://lore.kernel.org/all/20220823234353.937002-1-pshier@google.com/
>
> drivers/idle/intel_idle.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 3e101719689a..df129c73786f 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -187,12 +187,12 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev,
> int ret;
>
> if (smt_active)
> - wrmsrl(MSR_IA32_SPEC_CTRL, 0);
> + native_wrmsr(MSR_IA32_SPEC_CTRL, 0);
>
> ret = __intel_idle(dev, drv, index);
>
> if (smt_active)
> - wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl);
> + native_wrmsr(MSR_IA32_SPEC_CTRL, spec_ctrl);
>
> return ret;
> }
> --
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-08-24 23:42 [PATCH v2] intel_idle: avoid tracing MSR writes while idling Peter Shier
2022-08-25 8:41 ` Peter Zijlstra
2022-08-25 11:43 ` Rafael J. Wysocki
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