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Commit 8b306e2f authored by Paolo Bonzini's avatar Paolo Bonzini
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KVM: VMX: avoid double list add with VT-d posted interrupts 



In some cases, for example involving hot-unplug of assigned
devices, pi_post_block can forget to remove the vCPU from the
blocked_vcpu_list.  When this happens, the next call to
pi_pre_block corrupts the list.

Fix this in two ways.  First, check vcpu->pre_pcpu in pi_pre_block
and WARN instead of adding the element twice in the list.  Second,
always do the list removal in pi_post_block if vcpu->pre_pcpu is
set (not -1).

The new code keeps interrupts disabled for the whole duration of
pi_pre_block/pi_post_block.  This is not strictly necessary, but
easier to follow.  For the same reason, PI.ON is checked only
after the cmpxchg, and to handle it we just call the post-block
code.  This removes duplication of the list removal code.

Cc: Huangweidong <weidong.huang@huawei.com>
Cc: Gonglei <arei.gonglei@huawei.com>
Cc: wangxin <wangxinxin.wang@huawei.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Tested-by: default avatarLongpeng (Mike) <longpeng2@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent cd39e117

arch/x86/kvm/vmx.c

+25 −37
Original line number Diff line number Diff line
@@ -11710,10 +11710,11 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) 
	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);

	struct pi_desc old, new;

	unsigned int dest;

	unsigned long flags;



	do {

		old.control = new.control = pi_desc->control;

		WARN(old.nv != POSTED_INTR_WAKEUP_VECTOR,

		     "Wakeup handler not enabled while the VCPU is blocked\n");



		dest = cpu_physical_id(vcpu->cpu);
@@ -11730,14 +11731,10 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) 
	} while (cmpxchg(&pi_desc->control, old.control,

			new.control) != old.control);



	if(vcpu->pre_pcpu != -1) {

		spin_lock_irqsave(

			&per_cpu(blocked_vcpu_on_cpu_lock,

			vcpu->pre_pcpu), flags);

	if (!WARN_ON_ONCE(vcpu->pre_pcpu == -1)) {

		spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));

		list_del(&vcpu->blocked_vcpu_list);

		spin_unlock_irqrestore(

			&per_cpu(blocked_vcpu_on_cpu_lock,

			vcpu->pre_pcpu), flags);

		spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));

		vcpu->pre_pcpu = -1;

	}

}
@@ -11757,7 +11754,6 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) 
 */

static int pi_pre_block(struct kvm_vcpu *vcpu)

{

	unsigned long flags;

	unsigned int dest;

	struct pi_desc old, new;

	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
@@ -11767,34 +11763,20 @@ static int pi_pre_block(struct kvm_vcpu *vcpu) 
		!kvm_vcpu_apicv_active(vcpu))

		return 0;



	WARN_ON(irqs_disabled());

	local_irq_disable();

	if (!WARN_ON_ONCE(vcpu->pre_pcpu != -1)) {

		vcpu->pre_pcpu = vcpu->cpu;

	spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,

			  vcpu->pre_pcpu), flags);

		spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));

		list_add_tail(&vcpu->blocked_vcpu_list,

			      &per_cpu(blocked_vcpu_on_cpu,

				       vcpu->pre_pcpu));

	spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock,

			       vcpu->pre_pcpu), flags);

		spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));

	}



	do {

		old.control = new.control = pi_desc->control;



		/*

		 * We should not block the vCPU if

		 * an interrupt is posted for it.

		 */

		if (pi_test_on(pi_desc) == 1) {

			spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,

					  vcpu->pre_pcpu), flags);

			list_del(&vcpu->blocked_vcpu_list);

			spin_unlock_irqrestore(

					&per_cpu(blocked_vcpu_on_cpu_lock,

					vcpu->pre_pcpu), flags);

			vcpu->pre_pcpu = -1;



			return 1;

		}



		WARN((pi_desc->sn == 1),

		     "Warning: SN field of posted-interrupts "

		     "is set before blocking\n");
@@ -11819,7 +11801,12 @@ static int pi_pre_block(struct kvm_vcpu *vcpu) 
	} while (cmpxchg(&pi_desc->control, old.control,

			new.control) != old.control);



	return 0;

	/* We should not block the vCPU if an interrupt is posted for it.  */

	if (pi_test_on(pi_desc) == 1)

		__pi_post_block(vcpu);



	local_irq_enable();

	return (vcpu->pre_pcpu == -1);

}



static int vmx_pre_block(struct kvm_vcpu *vcpu)
@@ -11835,12 +11822,13 @@ static int vmx_pre_block(struct kvm_vcpu *vcpu) 


static void pi_post_block(struct kvm_vcpu *vcpu)

{

	if (!kvm_arch_has_assigned_device(vcpu->kvm) ||

		!irq_remapping_cap(IRQ_POSTING_CAP)  ||

		!kvm_vcpu_apicv_active(vcpu))

	if (vcpu->pre_pcpu == -1)

		return;



	WARN_ON(irqs_disabled());

	local_irq_disable();

	__pi_post_block(vcpu);

	local_irq_enable();

}



static void vmx_post_block(struct kvm_vcpu *vcpu)