Commit 33677aef authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86-core-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 core updates from Ingo Molnar:

 - Add comments about the magic behind the shadow STI
   before MWAIT in __sti_mwait().

 - Fix possible unintended timer delays caused by a race
   in mwait_idle_with_hints().

* tag 'x86-core-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram
  x86: Add a comment about the "magic" behind shadow sti before mwait
parents b51cc5d0 edc8fc01

arch/x86/include/asm/mwait.h

+18 −2
Original line number Diff line number Diff line
@@ -87,6 +87,15 @@ static __always_inline void __mwaitx(unsigned long eax, unsigned long ebx, 
		     :: "a" (eax), "b" (ebx), "c" (ecx));

}



/*

 * Re-enable interrupts right upon calling mwait in such a way that

 * no interrupt can fire _before_ the execution of mwait, ie: no

 * instruction must be placed between "sti" and "mwait".

 *

 * This is necessary because if an interrupt queues a timer before

 * executing mwait, it would otherwise go unnoticed and the next tick

 * would not be reprogrammed accordingly before mwait ever wakes up.

 */

static __always_inline void __sti_mwait(unsigned long eax, unsigned long ecx)

{

	mds_idle_clear_cpu_buffers();
@@ -115,8 +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())



		if (!need_resched()) {

			if (ecx & 1) {

				__mwait(eax, ecx);

			} else {

				__sti_mwait(eax, ecx);

				raw_local_irq_disable();

			}

		}

	}

	current_clr_polling();

}

drivers/idle/intel_idle.c

+7 −12
Original line number Diff line number Diff line
@@ -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);

}



/**