* [PATCH] x86/msr: add idle version of wrmsr trace
@ 2022-08-23 23:43 FirstName LastName
2022-08-24 6:48 ` Peter Zijlstra
0 siblings, 1 reply; 3+ messages in thread
From: FirstName LastName @ 2022-08-23 23:43 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
From: Peter Shier <pshier@google.com>
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.
Add idle versions of needed routines and change intel_idle_ibrs to use it.
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>
---
arch/x86/include/asm/msr.h | 16 ++++++++++++++++
arch/x86/lib/msr.c | 6 ++++++
drivers/idle/intel_idle.c | 4 ++--
3 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 65ec1965cd28..248cc58b7758 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -62,10 +62,12 @@ DECLARE_TRACEPOINT(read_msr);
DECLARE_TRACEPOINT(write_msr);
DECLARE_TRACEPOINT(rdpmc);
extern void do_trace_write_msr(unsigned int msr, u64 val, int failed);
+extern void do_trace_write_msr_idle(unsigned int msr, u64 val, int failed);
extern void do_trace_read_msr(unsigned int msr, u64 val, int failed);
extern void do_trace_rdpmc(unsigned int msr, u64 val, int failed);
#else
static inline void do_trace_write_msr(unsigned int msr, u64 val, int failed) {}
+extern void do_trace_write_msr_idle(unsigned int msr, u64 val, int failed) {}
static inline void do_trace_read_msr(unsigned int msr, u64 val, int failed) {}
static inline void do_trace_rdpmc(unsigned int msr, u64 val, int failed) {}
#endif
@@ -148,6 +150,15 @@ native_write_msr(unsigned int msr, u32 low, u32 high)
do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
}
+static inline void notrace
+native_write_msr_idle(unsigned int msr, u32 low, u32 high)
+{
+ __wrmsr(msr, low, high);
+
+ if (tracepoint_enabled(write_msr))
+ do_trace_write_msr_idle(msr, ((u64)high << 32 | low), 0);
+}
+
/* Can be uninlined because referenced by paravirt */
static inline int notrace
native_write_msr_safe(unsigned int msr, u32 low, u32 high)
@@ -262,6 +273,11 @@ static inline void wrmsrl(unsigned int msr, u64 val)
native_write_msr(msr, (u32)(val & 0xffffffffULL), (u32)(val >> 32));
}
+static inline void wrmsrl_idle(unsigned int msr, u64 val)
+{
+ native_write_msr_idle(msr, (u32)(val & 0xffffffffULL), (u32)(val >> 32));
+}
+
/* wrmsr with exception handling */
static inline int wrmsr_safe(unsigned int msr, u32 low, u32 high)
{
diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
index b09cd2ad426c..58fdf0f13850 100644
--- a/arch/x86/lib/msr.c
+++ b/arch/x86/lib/msr.c
@@ -121,6 +121,12 @@ void do_trace_write_msr(unsigned int msr, u64 val, int failed)
EXPORT_SYMBOL(do_trace_write_msr);
EXPORT_TRACEPOINT_SYMBOL(write_msr);
+void do_trace_write_msr_idle(unsigned int msr, u64 val, int failed)
+{
+ trace_write_msr_rcuidle(msr, val, failed);
+}
+EXPORT_SYMBOL(do_trace_write_msr_idle);
+
void do_trace_read_msr(unsigned int msr, u64 val, int failed)
{
trace_read_msr(msr, val, failed);
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 3e101719689a..bdecd2638c59 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);
+ wrmsrl_idle(MSR_IA32_SPEC_CTRL, 0);
ret = __intel_idle(dev, drv, index);
if (smt_active)
- wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl);
+ wrmsrl_idle(MSR_IA32_SPEC_CTRL, spec_ctrl);
return ret;
}
--
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/msr: add idle version of wrmsr trace
2022-08-23 23:43 [PATCH] x86/msr: add idle version of wrmsr trace FirstName LastName
@ 2022-08-24 6:48 ` Peter Zijlstra
2022-08-24 7:22 ` Peter Zijlstra
0 siblings, 1 reply; 3+ messages in thread
From: Peter Zijlstra @ 2022-08-24 6:48 UTC (permalink / raw)
To: FirstName LastName
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
Dear FirstName LastName, pleae fix your MUA.
On Tue, Aug 23, 2022 at 04:43:53PM -0700, FirstName LastName wrote:
> From: Peter Shier <pshier@google.com>
>
> 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.
>
No, the right thing here is to not do tracing at all.
*sigh* I should go finish this series:
https://lore.kernel.org/lkml/20220608142723.103523089@infradead.org/
---
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 3e101719689a..6e82b2df29cb 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] x86/msr: add idle version of wrmsr trace
2022-08-24 6:48 ` Peter Zijlstra
@ 2022-08-24 7:22 ` Peter Zijlstra
0 siblings, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2022-08-24 7:22 UTC (permalink / raw)
To: FirstName LastName
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 08:48:33AM +0200, Peter Zijlstra wrote:
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 3e101719689a..6e82b2df29cb 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;
> }
Clearly I should not be sending email before having wake-up-juice.. that
should of course be native_wrmsr(SPEC_CTRL, val, 0) etc..
^ permalink raw reply [flat|nested] 3+ messages in thread
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