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authorPeter Zijlstra <peterz@infradead.org>2023-11-15 10:13:23 -0500
committerPeter Zijlstra <peterz@infradead.org>2023-11-29 15:44:01 +0100
commitedc8fc01f608108b0b7580cb2c29dfb5135e5f0e (patch)
treec7b4fc57842e68df9706a6fb5194791875563b63
parent7d09a052a3bdb62de9a86d43359d6c22eeaf105a (diff)
x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram
intel_idle_irq() re-enables IRQs very early. As a result, an interrupt may fire before mwait() is eventually called. If such an interrupt queues a timer, it may go unnoticed until mwait returns and the idle loop handles the tick re-evaluation. And monitoring TIF_NEED_RESCHED doesn't help because a local timer enqueue doesn't set that flag. The issue is mitigated by the fact that this idle handler is only invoked for shallow C-states when, presumably, the next tick is supposed to be close enough. There may still be rare cases though when the next tick is far away and the selected C-state is shallow, resulting in a timer getting ignored for a while. Fix this with using sti_mwait() whose IRQ-reenablement only triggers upon calling mwait(), dealing with the race while keeping the interrupt latency within acceptable bounds. Fixes: c227233ad64c (intel_idle: enable interrupts before C1 on Xeons) Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Rafael J. Wysocki <rafael@kernel.org> Link: https://lkml.kernel.org/r/20231115151325.6262-3-frederic@kernel.org
-rw-r--r--arch/x86/include/asm/mwait.h11
-rw-r--r--drivers/idle/intel_idle.c19
2 files changed, 16 insertions, 14 deletions
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 341ee4f1d91e..920426d691ce 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -124,8 +124,15 @@ static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned lo
}
__monitor((void *)&current_thread_info()->flags, 0, 0);
- if (!need_resched())
- __mwait(eax, ecx);
+
+ if (!need_resched()) {
+ if (ecx & 1) {
+ __mwait(eax, ecx);
+ } else {
+ __sti_mwait(eax, ecx);
+ raw_local_irq_disable();
+ }
+ }
}
current_clr_polling();
}
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index dcda0afecfc5..3e01a6b23e75 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -131,11 +131,12 @@ static unsigned int mwait_substates __initdata;
#define MWAIT2flg(eax) ((eax & 0xFF) << 24)
static __always_inline int __intel_idle(struct cpuidle_device *dev,
- struct cpuidle_driver *drv, int index)
+ struct cpuidle_driver *drv,
+ int index, bool irqoff)
{
struct cpuidle_state *state = &drv->states[index];
unsigned long eax = flg2MWAIT(state->flags);
- unsigned long ecx = 1; /* break on interrupt flag */
+ unsigned long ecx = 1*irqoff; /* break on interrupt flag */
mwait_idle_with_hints(eax, ecx);
@@ -159,19 +160,13 @@ static __always_inline int __intel_idle(struct cpuidle_device *dev,
static __cpuidle int intel_idle(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
{
- return __intel_idle(dev, drv, index);
+ return __intel_idle(dev, drv, index, true);
}
static __cpuidle int intel_idle_irq(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
{
- int ret;
-
- raw_local_irq_enable();
- ret = __intel_idle(dev, drv, index);
- raw_local_irq_disable();
-
- return ret;
+ return __intel_idle(dev, drv, index, false);
}
static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev,
@@ -184,7 +179,7 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev,
if (smt_active)
__update_spec_ctrl(0);
- ret = __intel_idle(dev, drv, index);
+ ret = __intel_idle(dev, drv, index, true);
if (smt_active)
__update_spec_ctrl(spec_ctrl);
@@ -196,7 +191,7 @@ static __cpuidle int intel_idle_xstate(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
{
fpu_idle_fpregs();
- return __intel_idle(dev, drv, index);
+ return __intel_idle(dev, drv, index, true);
}
/**