lkml.org 
[lkml]   [2022]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH] x86/msr: add idle version of wrmsr trace
From
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;
}
--

\
 
 \ /
  Last update: 2022-08-24 01:44    [W:0.038 / U:0.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site