KVM: arm64: vgic: Check that new ITEs could be saved in guest memory

Try to improve the predictability of ITS save/restores by failing
commands that would lead to failed saves. More specifically, fail any
command that adds an entry into an ITS table that is not in guest
memory, which would otherwise lead to a failed ITS save ioctl. There
are already checks for collection and device entries, but not for
ITEs.  Add the corresponding check for the ITT when adding ITEs.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220510001633.552496-2-ricarkol@google.com

arch/arm64/kvm/vgic/vgic-its.c

@@ -894,6 +894,18 @@ static int vgic_its_cmd_handle_movi(struct kvm *kvm, struct vgic_its *its,
 	return update_affinity(ite->irq, vcpu);
 }
 
+static bool __is_visible_gfn_locked(struct vgic_its *its, gpa_t gpa)
+{
+	gfn_t gfn = gpa >> PAGE_SHIFT;
+	int idx;
+	bool ret;
+
+	idx = srcu_read_lock(&its->dev->kvm->srcu);
+	ret = kvm_is_visible_gfn(its->dev->kvm, gfn);
+	srcu_read_unlock(&its->dev->kvm->srcu, idx);
+	return ret;
+}
+
 /*
  * Check whether an ID can be stored into the corresponding guest table.
  * For a direct table this is pretty easy, but gets a bit nasty for
@@ -908,9 +920,7 @@ static bool vgic_its_check_id(struct vgic_its *its, u64 baser, u32 id,
 	u64 indirect_ptr, type = GITS_BASER_TYPE(baser);
 	phys_addr_t base = GITS_BASER_ADDR_48_to_52(baser);
 	int esz = GITS_BASER_ENTRY_SIZE(baser);
-	int index, idx;
-	gfn_t gfn;
-	bool ret;
+	int index;
 
 	switch (type) {
 	case GITS_BASER_TYPE_DEVICE:
@@ -933,12 +943,11 @@ static bool vgic_its_check_id(struct vgic_its *its, u64 baser, u32 id,
 			return false;
 
 		addr = base + id * esz;
-		gfn = addr >> PAGE_SHIFT;
 
 		if (eaddr)
 			*eaddr = addr;
 
-		goto out;
+		return __is_visible_gfn_locked(its, addr);
 	}
 
 	/* calculate and check the index into the 1st level */
@@ -964,16 +973,30 @@ static bool vgic_its_check_id(struct vgic_its *its, u64 baser, u32 id,
 	/* Find the address of the actual entry */
 	index = id % (SZ_64K / esz);
 	indirect_ptr += index * esz;
-	gfn = indirect_ptr >> PAGE_SHIFT;
 
 	if (eaddr)
 		*eaddr = indirect_ptr;
 
-out:
-	idx = srcu_read_lock(&its->dev->kvm->srcu);
-	ret = kvm_is_visible_gfn(its->dev->kvm, gfn);
-	srcu_read_unlock(&its->dev->kvm->srcu, idx);
-	return ret;
+	return __is_visible_gfn_locked(its, indirect_ptr);
+}
+
+/*
+ * Check whether an event ID can be stored in the corresponding Interrupt
+ * Translation Table, which starts at device->itt_addr.
+ */
+static bool vgic_its_check_event_id(struct vgic_its *its, struct its_device *device,
+		u32 event_id)
+{
+	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
+	int ite_esz = abi->ite_esz;
+	gpa_t gpa;
+
+	/* max table size is: BIT_ULL(device->num_eventid_bits) * ite_esz */
+	if (event_id >= BIT_ULL(device->num_eventid_bits))
+		return false;
+
+	gpa = device->itt_addr + event_id * ite_esz;
+	return __is_visible_gfn_locked(its, gpa);
 }
 
 static int vgic_its_alloc_collection(struct vgic_its *its,
@@ -1061,7 +1084,7 @@ static int vgic_its_cmd_handle_mapi(struct kvm *kvm, struct vgic_its *its,
 	if (!device)
 		return E_ITS_MAPTI_UNMAPPED_DEVICE;
 
-	if (event_id >= BIT_ULL(device->num_eventid_bits))
+	if (!vgic_its_check_event_id(its, device, event_id))
 		return E_ITS_MAPTI_ID_OOR;
 
 	if (its_cmd_get_command(its_cmd) == GITS_CMD_MAPTI)