KVM: arm/arm64: Properly protect VGIC locks from IRQs

As Jan reported [1], lockdep complains about the VGIC not being bullet
proof. This seems to be due to two issues:
- When commit 006df0f34930 ("KVM: arm/arm64: Support calling
  vgic_update_irq_pending from irq context") promoted irq_lock and
  ap_list_lock to _irqsave, we forgot two instances of irq_lock.
  lockdeps seems to pick those up.
- If a lock is _irqsave, any other locks we take inside them should be
  _irqsafe as well. So the lpi_list_lock needs to be promoted also.

This fixes both issues by simply making the remaining instances of those
locks _irqsave.
One irq_lock is addressed in a separate patch, to simplify backporting.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/575718.html

Cc: stable@vger.kernel.org
Fixes: 006df0f34930 ("KVM: arm/arm64: Support calling vgic_update_irq_pending from irq context")
Reported-by: Jan Glauber <jan.glauber@caviumnetworks.com>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index a8f07243aa9f..41abf92f2699 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -52,6 +52,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
 	struct vgic_irq *irq = vgic_get_irq(kvm, NULL, intid), *oldirq;
+	unsigned long flags;
 	int ret;
 
 	/* In this case there is no put, since we keep the reference. */
@@ -71,7 +72,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 	irq->intid = intid;
 	irq->target_vcpu = vcpu;
 
-	spin_lock(&dist->lpi_list_lock);
+	spin_lock_irqsave(&dist->lpi_list_lock, flags);
 
 	/*
 	 * There could be a race with another vgic_add_lpi(), so we need to
@@ -99,7 +100,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 	dist->lpi_list_count++;
 
 out_unlock:
-	spin_unlock(&dist->lpi_list_lock);
+	spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
 	/*
 	 * We "cache" the configuration table entries in our struct vgic_irq's.
@@ -315,6 +316,7 @@ static int vgic_copy_lpi_list(struct kvm_vcpu *vcpu, u32 **intid_ptr)
 {
 	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
 	struct vgic_irq *irq;
+	unsigned long flags;
 	u32 *intids;
 	int irq_count, i = 0;
 
@@ -330,7 +332,7 @@ static int vgic_copy_lpi_list(struct kvm_vcpu *vcpu, u32 **intid_ptr)
 	if (!intids)
 		return -ENOMEM;
 
-	spin_lock(&dist->lpi_list_lock);
+	spin_lock_irqsave(&dist->lpi_list_lock, flags);
 	list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
 		if (i == irq_count)
 			break;
@@ -339,7 +341,7 @@ static int vgic_copy_lpi_list(struct kvm_vcpu *vcpu, u32 **intid_ptr)
 			continue;
 		intids[i++] = irq->intid;
 	}
-	spin_unlock(&dist->lpi_list_lock);
+	spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
 	*intid_ptr = intids;
 	return i;