* [PATCH v8 0/2] x86/apic: x2apic write eoi msr notrace
@ 2016-11-07 3:13 Wanpeng Li
2016-11-07 3:13 ` [PATCH v8 1/2] x86/msr: Add write " Wanpeng Li
2016-11-07 3:13 ` [PATCH v8 2/2] x86/apic: x2apic write eoi msr notrace Wanpeng Li
0 siblings, 2 replies; 5+ messages in thread
From: Wanpeng Li @ 2016-11-07 3:13 UTC (permalink / raw)
To: linux-kernel, kvm
Cc: Ingo Molnar, Mike Galbraith, Peter Zijlstra, Thomas Gleixner,
Paolo Bonzini, Borislav Petkov, Wanpeng Li
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 0
RCU used illegally from extended quiescent state!
no locks held by swapper/1/0.
do_trace_write_msr
native_write_msr
native_apic_msr_eoi_write
smp_reschedule_interrupt
reschedule_interrupt
Reschedule interrupt may be called in CPU idle state. This causes lockdep
check warning above.
As Peterz pointed out:
| The thing is, many many smp_reschedule_interrupt() invocations don't
| actually execute anything much at all and are only sent to tickle the
| return to user path (which does the actual preemption).
|
| Having to do the whole irq_enter/irq_exit dance just for this unlikely
| debug case totally blows.
This patchset adds x2apic write eoi msr notrace to avoid the debug codes
splash and reverts irq_enter/irq_exit dance to avoid to make a very frequent
interrupt slower because of debug code.
v7 -> v8:
* cleanup patch 2/2 descriptions
v6 -> v7:
* cleanup storage class should be at the beginning of the declaration
v5 -> v6:
* split the patch
* don't duplicate the inline asm
v4 -> v5:
* add notrace mark
v3 -> v4:
* add notrace mark
v2 -> v3:
* revert irq_enter/irq_exit() since it is merged
v1 -> v2:
* add write msr notrace to avoid debug codes splash instead of slowdown
a very frequent interrupt
Wanpeng Li (2):
x86/msr: Add write msr notrace
x86/apic: x2apic write eoi msr notrace
arch/x86/include/asm/apic.h | 3 ++-
arch/x86/include/asm/msr.h | 14 +++++++++++++-
arch/x86/kernel/apic/apic.c | 1 +
arch/x86/kernel/kvm.c | 4 ++--
arch/x86/kernel/smp.c | 2 --
5 files changed, 18 insertions(+), 6 deletions(-)
--
1.9.1
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v8 1/2] x86/msr: Add write msr notrace
2016-11-07 3:13 [PATCH v8 0/2] x86/apic: x2apic write eoi msr notrace Wanpeng Li
@ 2016-11-07 3:13 ` Wanpeng Li
2016-11-09 21:09 ` [tip:x86/apic] x86/msr: Add wrmsr_notrace() tip-bot for Wanpeng Li
2016-11-07 3:13 ` [PATCH v8 2/2] x86/apic: x2apic write eoi msr notrace Wanpeng Li
1 sibling, 1 reply; 5+ messages in thread
From: Wanpeng Li @ 2016-11-07 3:13 UTC (permalink / raw)
To: linux-kernel, kvm
Cc: Ingo Molnar, Mike Galbraith, Peter Zijlstra, Thomas Gleixner,
Paolo Bonzini, Borislav Petkov, Wanpeng Li
From: Wanpeng Li <wanpeng.li@hotmail.com>
Add write msr notrace, it will be used by later patch.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
arch/x86/include/asm/msr.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index b5fee97..eec29a7 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -115,17 +115,29 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
}
/* Can be uninlined because referenced by paravirt */
-notrace static inline void native_write_msr(unsigned int msr,
+static notrace inline void __native_write_msr_notrace(unsigned int msr,
unsigned low, unsigned high)
{
asm volatile("1: wrmsr\n"
"2:\n"
_ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
: : "c" (msr), "a"(low), "d" (high) : "memory");
+}
+
+/* Can be uninlined because referenced by paravirt */
+static notrace inline void native_write_msr(unsigned int msr,
+ unsigned low, unsigned high)
+{
+ __native_write_msr_notrace(msr, low, high);
if (msr_tracepoint_active(__tracepoint_write_msr))
do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
}
+static inline void wrmsr_notrace(unsigned msr, unsigned low, unsigned high)
+{
+ __native_write_msr_notrace(msr, low, high);
+}
+
/* Can be uninlined because referenced by paravirt */
notrace static inline int native_write_msr_safe(unsigned int msr,
unsigned low, unsigned high)
--
1.9.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v8 2/2] x86/apic: x2apic write eoi msr notrace
2016-11-07 3:13 [PATCH v8 0/2] x86/apic: x2apic write eoi msr notrace Wanpeng Li
2016-11-07 3:13 ` [PATCH v8 1/2] x86/msr: Add write " Wanpeng Li
@ 2016-11-07 3:13 ` Wanpeng Li
2016-11-09 21:10 ` [tip:x86/apic] x86/apic: Prevent tracing on apic_msr_write_eoi() tip-bot for Wanpeng Li
1 sibling, 1 reply; 5+ messages in thread
From: Wanpeng Li @ 2016-11-07 3:13 UTC (permalink / raw)
To: linux-kernel, kvm
Cc: Ingo Molnar, Mike Galbraith, Peter Zijlstra, Thomas Gleixner,
Paolo Bonzini, Borislav Petkov, Wanpeng Li
From: Wanpeng Li <wanpeng.li@hotmail.com>
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 0
RCU used illegally from extended quiescent state!
no locks held by swapper/1/0.
do_trace_write_msr
native_write_msr
native_apic_msr_eoi_write
smp_reschedule_interrupt
reschedule_interrupt
Reschedule interrupt may be called in CPU idle state. This causes lockdep
check warning above.
As Peterz pointed out:
| So now we're making a very frequent interrupt slower because of debug
| code.
|
| The thing is, many many smp_reschedule_interrupt() invocations don't
| actually execute anything much at all and are only sent to tickle the
| return to user path (which does the actual preemption).
|
| Having to do the whole irq_enter/irq_exit dance just for this unlikely
| debug case totally blows.
This patch converts x2apic write eoi msr to notrace to avoid the debug
codes splash and reverts irq_enter/irq_exit dance to avoid to make a very
frequent interrupt slower because of debug code.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
arch/x86/include/asm/apic.h | 3 ++-
arch/x86/kernel/apic/apic.c | 1 +
arch/x86/kernel/kvm.c | 4 ++--
arch/x86/kernel/smp.c | 2 --
4 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index f5aaf6c..a5a0bcf 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -196,7 +196,7 @@ static inline void native_apic_msr_write(u32 reg, u32 v)
static inline void native_apic_msr_eoi_write(u32 reg, u32 v)
{
- wrmsr(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
+ wrmsr_notrace(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
}
static inline u32 native_apic_msr_read(u32 reg)
@@ -332,6 +332,7 @@ struct apic {
* on write for EOI.
*/
void (*eoi_write)(u32 reg, u32 v);
+ void (*native_eoi_write)(u32 reg, u32 v);
u64 (*icr_read)(void);
void (*icr_write)(u32 low, u32 high);
void (*wait_icr_idle)(void);
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 88c657b..2686894 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2263,6 +2263,7 @@ void __init apic_set_eoi_write(void (*eoi_write)(u32 reg, u32 v))
for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
/* Should happen once for each apic */
WARN_ON((*drv)->eoi_write == eoi_write);
+ (*drv)->native_eoi_write = (*drv)->eoi_write;
(*drv)->eoi_write = eoi_write;
}
}
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index edbbfc8..d230513 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -308,7 +308,7 @@ static void kvm_register_steal_time(void)
static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
-static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
+static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val)
{
/**
* This relies on __test_and_clear_bit to modify the memory
@@ -319,7 +319,7 @@ static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
*/
if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
return;
- apic_write(APIC_EOI, APIC_EOI_ACK);
+ apic->native_eoi_write(APIC_EOI, APIC_EOI_ACK);
}
static void kvm_guest_cpu_init(void)
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index c00cb64..68f8cc2 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -261,10 +261,8 @@ static inline void __smp_reschedule_interrupt(void)
__visible void smp_reschedule_interrupt(struct pt_regs *regs)
{
- irq_enter();
ack_APIC_irq();
__smp_reschedule_interrupt();
- irq_exit();
/*
* KVM uses this interrupt to force a cpu out of guest mode
*/
--
1.9.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip:x86/apic] x86/msr: Add wrmsr_notrace()
2016-11-07 3:13 ` [PATCH v8 1/2] x86/msr: Add write " Wanpeng Li
@ 2016-11-09 21:09 ` tip-bot for Wanpeng Li
0 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Wanpeng Li @ 2016-11-09 21:09 UTC (permalink / raw)
To: linux-tip-commits
Cc: pbonzini, mingo, linux-kernel, efault, tglx, bp, peterz, wanpeng.li, hpa
Commit-ID: b2c5ea4f759190ee9f75687a00035c1a66d0d743
Gitweb: http://git.kernel.org/tip/b2c5ea4f759190ee9f75687a00035c1a66d0d743
Author: Wanpeng Li <wanpeng.li@hotmail.com>
AuthorDate: Mon, 7 Nov 2016 11:13:39 +0800
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 9 Nov 2016 22:03:14 +0100
x86/msr: Add wrmsr_notrace()
Required to remove the extra irq_enter()/irq_exit() in
smp_reschedule_interrupt().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: kvm@vger.kernel.org
Cc: Mike Galbraith <efault@gmx.de>
Link: http://lkml.kernel.org/r/1478488420-5982-2-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/msr.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index b5fee97..9b0a232 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -115,17 +115,29 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
}
/* Can be uninlined because referenced by paravirt */
-notrace static inline void native_write_msr(unsigned int msr,
+static notrace inline void __native_write_msr_notrace(unsigned int msr,
unsigned low, unsigned high)
{
asm volatile("1: wrmsr\n"
"2:\n"
_ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
: : "c" (msr), "a"(low), "d" (high) : "memory");
+}
+
+/* Can be uninlined because referenced by paravirt */
+static notrace inline void native_write_msr(unsigned int msr,
+ unsigned low, unsigned high)
+{
+ __native_write_msr_notrace(msr, low, high);
if (msr_tracepoint_active(__tracepoint_write_msr))
do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
}
+static inline void wrmsr_notrace(unsigned msr, unsigned low, unsigned high)
+{
+ __native_write_msr_notrace(msr, low, high);
+}
+
/* Can be uninlined because referenced by paravirt */
notrace static inline int native_write_msr_safe(unsigned int msr,
unsigned low, unsigned high)
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip:x86/apic] x86/apic: Prevent tracing on apic_msr_write_eoi()
2016-11-07 3:13 ` [PATCH v8 2/2] x86/apic: x2apic write eoi msr notrace Wanpeng Li
@ 2016-11-09 21:10 ` tip-bot for Wanpeng Li
0 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Wanpeng Li @ 2016-11-09 21:10 UTC (permalink / raw)
To: linux-tip-commits
Cc: peterz, pbonzini, efault, wanpeng.li, linux-kernel, bp, mingo, hpa, tglx
Commit-ID: 8ca225520e278e41396dab0524989f4848626f83
Gitweb: http://git.kernel.org/tip/8ca225520e278e41396dab0524989f4848626f83
Author: Wanpeng Li <wanpeng.li@hotmail.com>
AuthorDate: Mon, 7 Nov 2016 11:13:40 +0800
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 9 Nov 2016 22:03:14 +0100
x86/apic: Prevent tracing on apic_msr_write_eoi()
The following RCU lockdep warning led to adding irq_enter()/irq_exit() into
smp_reschedule_interrupt():
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 0
RCU used illegally from extended quiescent state!
no locks held by swapper/1/0.
do_trace_write_msr
native_write_msr
native_apic_msr_eoi_write
smp_reschedule_interrupt
reschedule_interrupt
As Peterz pointed out:
| So now we're making a very frequent interrupt slower because of debug
| code.
|
| The thing is, many many smp_reschedule_interrupt() invocations don't
| actually execute anything much at all and are only sent to tickle the
| return to user path (which does the actual preemption).
|
| Having to do the whole irq_enter/irq_exit dance just for this unlikely
| debug case totally blows.
Use the wrmsr_notrace() variant in native_apic_msr_write_eoi, annotate the
kvm variant with notrace and add a native_apic_eoi callback to the apic
structure so KVM guests are covered as well.
This allows to revert the irq_enter/irq_exit dance in
smp_reschedule_interrupt().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Mike Galbraith <efault@gmx.de>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1478488420-5982-3-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/apic.h | 3 ++-
arch/x86/kernel/apic/apic.c | 1 +
arch/x86/kernel/kvm.c | 4 ++--
arch/x86/kernel/smp.c | 2 --
4 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index f5aaf6c..a5a0bcf 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -196,7 +196,7 @@ static inline void native_apic_msr_write(u32 reg, u32 v)
static inline void native_apic_msr_eoi_write(u32 reg, u32 v)
{
- wrmsr(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
+ wrmsr_notrace(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
}
static inline u32 native_apic_msr_read(u32 reg)
@@ -332,6 +332,7 @@ struct apic {
* on write for EOI.
*/
void (*eoi_write)(u32 reg, u32 v);
+ void (*native_eoi_write)(u32 reg, u32 v);
u64 (*icr_read)(void);
void (*icr_write)(u32 low, u32 high);
void (*wait_icr_idle)(void);
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 88c657b..2686894 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2263,6 +2263,7 @@ void __init apic_set_eoi_write(void (*eoi_write)(u32 reg, u32 v))
for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
/* Should happen once for each apic */
WARN_ON((*drv)->eoi_write == eoi_write);
+ (*drv)->native_eoi_write = (*drv)->eoi_write;
(*drv)->eoi_write = eoi_write;
}
}
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index edbbfc8..aad52f1 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -308,7 +308,7 @@ static void kvm_register_steal_time(void)
static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
-static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
+static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val)
{
/**
* This relies on __test_and_clear_bit to modify the memory
@@ -319,7 +319,7 @@ static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
*/
if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
return;
- apic_write(APIC_EOI, APIC_EOI_ACK);
+ apic->native_eoi_write(APIC_EOI, APIC_EOI_ACK);
}
static void kvm_guest_cpu_init(void)
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index c00cb64..68f8cc2 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -261,10 +261,8 @@ static inline void __smp_reschedule_interrupt(void)
__visible void smp_reschedule_interrupt(struct pt_regs *regs)
{
- irq_enter();
ack_APIC_irq();
__smp_reschedule_interrupt();
- irq_exit();
/*
* KVM uses this interrupt to force a cpu out of guest mode
*/
^ permalink raw reply related [flat|nested] 5+ messages in thread
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