Commit 4de5c54f authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: nVMX: clean up posted interrupt descriptor try_cmpxchg 



Rely on try_cmpxchg64 for re-reading the PID on failure, using READ_ONCE
only right before the first iteration.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4b88b1a5

arch/x86/kvm/vmx/posted_intr.c

+8 −7
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu) 
	return &(to_vmx(vcpu)->pi_desc);

}



static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new)

static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)

{

	/*

	 * PID.ON can be set at any time by a different vCPU or by hardware,
@@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) 
	 * update must be retried with a fresh snapshot an ON change causes

	 * the cmpxchg to fail.

	 */

	if (!try_cmpxchg64(&pi_desc->control, &old, new))

	if (!try_cmpxchg64(&pi_desc->control, pold, new))

		return -EBUSY;



	return 0;
@@ -96,8 +96,9 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) 
	if (!x2apic_mode)

		dest = (dest << 8) & 0xFF00;



	old.control = READ_ONCE(pi_desc->control);

	do {

		old.control = new.control = READ_ONCE(pi_desc->control);

		new.control = old.control;



		/*

		 * Clear SN (as above) and refresh the destination APIC ID to
@@ -111,7 +112,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) 
		 * descriptor was modified on "put" to use the wakeup vector.

		 */

		new.nv = POSTED_INTR_VECTOR;

	} while (pi_try_set_control(pi_desc, old.control, new.control));

	} while (pi_try_set_control(pi_desc, &old.control, new.control));



	local_irq_restore(flags);
@@ -156,12 +157,12 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu) 


	WARN(pi_desc->sn, "PI descriptor SN field set before blocking");



	old.control = READ_ONCE(pi_desc->control);

	do {

		old.control = new.control = READ_ONCE(pi_desc->control);



		/* set 'NV' to 'wakeup vector' */

		new.control = old.control;

		new.nv = POSTED_INTR_WAKEUP_VECTOR;

	} while (pi_try_set_control(pi_desc, old.control, new.control));

	} while (pi_try_set_control(pi_desc, &old.control, new.control));



	/*

	 * Send a wakeup IPI to this CPU if an interrupt may have been posted