[RFC PATCH v1 1/4] irqchip/gic-v4.1: Plumb get_irqchip_state VLPI callback

[Shenming Lu <lushenming@huawei.com>]

From: Zenghui Yu <yuzenghui@huawei.com>

Up to now, the irq_get_irqchip_state() callback of its_irq_chip
leaves unimplemented since there is no architectural way to get
the VLPI's pending state before GICv4.1. Yeah, there has one in
v4.1 for VLPIs.

With GICv4.1, after unmapping the vPE, which cleans and invalidates
any caching of the VPT, we can get the VLPI's pending state by
peeking at the VPT. So we implement the irq_get_irqchip_state()
callback of its_irq_chip to do it.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Shenming Lu <lushenming@huawei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 38 ++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 0fec31931e11..287003cacac7 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1695,6 +1695,43 @@ static void its_irq_compose_msi_msg(struct irq_data *d, struct msi_msg *msg)
 	iommu_dma_compose_msi_msg(irq_data_get_msi_desc(d), msg);
 }
 
+static bool its_peek_vpt(struct its_vpe *vpe, irq_hw_number_t hwirq)
+{
+	int mask = hwirq % BITS_PER_BYTE;
+	void *va;
+	u8 *pt;
+
+	va = page_address(vpe->vpt_page);
+	pt = va + hwirq / BITS_PER_BYTE;
+
+	return !!(*pt & (1U << mask));
+}
+
+static int its_irq_get_irqchip_state(struct irq_data *d,
+				     enum irqchip_irq_state which, bool *val)
+{
+	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
+	struct its_vlpi_map *map = get_vlpi_map(d);
+
+	if (which != IRQCHIP_STATE_PENDING)
+		return -EINVAL;
+
+	/* not intended for physical LPI's pending state */
+	if (!map)
+		return -EINVAL;
+
+	/*
+	 * In GICv4.1, a VMAPP with {V,Alloc}=={0,1} cleans and invalidates
+	 * any caching of the VPT associated with the vPEID held in the GIC.
+	 */
+	if (!is_v4_1(its_dev->its) || atomic_read(&map->vpe->vmapp_count))
+		return -EACCES;
+
+	*val = its_peek_vpt(map->vpe, map->vintid);
+
+	return 0;
+}
+
 static int its_irq_set_irqchip_state(struct irq_data *d,
 				     enum irqchip_irq_state which,
 				     bool state)
@@ -1975,6 +2012,7 @@ static struct irq_chip its_irq_chip = {
 	.irq_eoi		= irq_chip_eoi_parent,
 	.irq_set_affinity	= its_set_affinity,
 	.irq_compose_msi_msg	= its_irq_compose_msi_msg,
+	.irq_get_irqchip_state	= its_irq_get_irqchip_state,
 	.irq_set_irqchip_state	= its_irq_set_irqchip_state,
 	.irq_retrigger		= its_irq_retrigger,
 	.irq_set_vcpu_affinity	= its_irq_set_vcpu_affinity,
-- 
2.23.0