irqchip/gic-v3-its: Synchronise INT/CLEAR commands targetting a VLPI using VSYNC

We have so far always injected/cleared VLPIs using either
INT+SYNC or CLEAR+SYNC sequences, but that's pretty wrong
for two reasons:

- SYNC only synchronises physical LPIs
- The collection ID that for the associated LPI doesn't match
  the redistributor the vPE is associated with

Instead, send an {INT,CLEAR}+VSYNC for forwarded LPIs, ensuring
that the ITS synchronises against the virtual pending table.
Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191108165805.3071-10-maz@kernel.org

drivers/irqchip/irq-gic-v3-its.c

@@ -721,6 +721,42 @@ static struct its_vpe *its_build_vinv_cmd(struct its_node *its,
 	return valid_vpe(its, map->vpe);
 }
 
+static struct its_vpe *its_build_vint_cmd(struct its_node *its,
+					  struct its_cmd_block *cmd,
+					  struct its_cmd_desc *desc)
+{
+	struct its_vlpi_map *map;
+
+	map = dev_event_to_vlpi_map(desc->its_int_cmd.dev,
+				    desc->its_int_cmd.event_id);
+
+	its_encode_cmd(cmd, GITS_CMD_INT);
+	its_encode_devid(cmd, desc->its_int_cmd.dev->device_id);
+	its_encode_event_id(cmd, desc->its_int_cmd.event_id);
+
+	its_fixup_cmd(cmd);
+
+	return valid_vpe(its, map->vpe);
+}
+
+static struct its_vpe *its_build_vclear_cmd(struct its_node *its,
+					    struct its_cmd_block *cmd,
+					    struct its_cmd_desc *desc)
+{
+	struct its_vlpi_map *map;
+
+	map = dev_event_to_vlpi_map(desc->its_clear_cmd.dev,
+				    desc->its_clear_cmd.event_id);
+
+	its_encode_cmd(cmd, GITS_CMD_CLEAR);
+	its_encode_devid(cmd, desc->its_clear_cmd.dev->device_id);
+	its_encode_event_id(cmd, desc->its_clear_cmd.event_id);
+
+	its_fixup_cmd(cmd);
+
+	return valid_vpe(its, map->vpe);
+}
+
 static u64 its_cmd_ptr_to_offset(struct its_node *its,
 				 struct its_cmd_block *ptr)
 {
@@ -1101,6 +1137,34 @@ static void its_send_vinv(struct its_device *dev, u32 event_id)
 	its_send_single_vcommand(dev->its, its_build_vinv_cmd, &desc);
 }
 
+static void its_send_vint(struct its_device *dev, u32 event_id)
+{
+	struct its_cmd_desc desc;
+
+	/*
+	 * There is no real VINT command. This is just a normal INT,
+	 * with a VSYNC instead of a SYNC.
+	 */
+	desc.its_int_cmd.dev = dev;
+	desc.its_int_cmd.event_id = event_id;
+
+	its_send_single_vcommand(dev->its, its_build_vint_cmd, &desc);
+}
+
+static void its_send_vclear(struct its_device *dev, u32 event_id)
+{
+	struct its_cmd_desc desc;
+
+	/*
+	 * There is no real VCLEAR command. This is just a normal CLEAR,
+	 * with a VSYNC instead of a SYNC.
+	 */
+	desc.its_clear_cmd.dev = dev;
+	desc.its_clear_cmd.event_id = event_id;
+
+	its_send_single_vcommand(dev->its, its_build_vclear_cmd, &desc);
+}
+
 /*
  * irqchip functions - assumes MSI, mostly.
  */
@@ -1294,10 +1358,17 @@ static int its_irq_set_irqchip_state(struct irq_data *d,
 	if (which != IRQCHIP_STATE_PENDING)
 		return -EINVAL;
 
+	if (irqd_is_forwarded_to_vcpu(d)) {
+		if (state)
+			its_send_vint(its_dev, event);
+		else
+			its_send_vclear(its_dev, event);
+	} else {
 		if (state)
 			its_send_int(its_dev, event);
 		else
 			its_send_clear(its_dev, event);
+	}
 
 	return 0;
 }