[PATCH v3 3/4] KVM: arm64: vgic-its: Clear ITE when DISCARD frees an ITE

[Jing Zhang]

From: Kunkun Jiang <jiangkunkun at huawei.com>

When DISCARD frees an ITE, it does not invalidate the
corresponding ITE. In the scenario of continuous saves and
restores, there may be a situation where an ITE is not saved
but is restored. This is unreasonable and may cause restore
to fail. This patch clears the corresponding ITE when DISCARD
frees an ITE.

Signed-off-by: Kunkun Jiang <jiangkunkun at huawei.com>
Signed-off-by: Jing Zhang <jingzhangos at google.com>
---
 arch/arm64/kvm/vgic/vgic-its.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index 7c57c7c6fbff..df8408ceae30 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -782,6 +782,10 @@ static int vgic_its_cmd_handle_discard(struct kvm *kvm, struct vgic_its *its,
 
 	ite = find_ite(its, device_id, event_id);
 	if (ite && its_is_collection_mapped(ite->collection)) {
+		struct its_device *device = find_its_device(its, device_id);
+		int ite_esz = vgic_its_get_abi(its)->ite_esz;
+		gpa_t gpa = device->itt_addr + ite->event_id * ite_esz;
+		u64 val = 0;
 		/*
 		 * Though the spec talks about removing the pending state, we
 		 * don't bother here since we clear the ITTE anyway and the
@@ -790,6 +794,11 @@ static int vgic_its_cmd_handle_discard(struct kvm *kvm, struct vgic_its *its,
 		vgic_its_invalidate_cache(its);
 
 		its_free_ite(kvm, ite);
+
+		if (KVM_BUG_ON(ite_esz != sizeof(val), kvm))
+			return -EINVAL;
+
+		vgic_write_guest_lock(kvm, gpa, &val, ite_esz);
 		return 0;
 	}
 
-- 
2.47.0.277.g8800431eea-goog