Re: [PATCH] irqchip/gic-v3-its: Don't confuse get_vlpi_map() by writing DB config

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Hi Zenghui,

Thanks for this.

On 2020-01-22 08:56, Zenghui Yu wrote:
When we're writing config for the doorbell interrupt, get_vlpi_map() will get confused by doorbell's d->parent_data hack and find the wrong its_dev
as chip data and the wrong event.

Fix this issue by making sure no doorbells will be involved before invoking
get_vlpi_map(), which restore some of the logic in lpi_write_config().

Fixes: c1d4d5cd203c ("irqchip/gic-v3-its: Add its_vlpi_map helpers")
Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
---

This is based on mainline and can't be directly applied to the current
irqchip-next.

 drivers/irqchip/irq-gic-v3-its.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index e05673bcd52b..cc8a4fcbd6d6 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1181,12 +1181,13 @@ static struct its_vlpi_map
*get_vlpi_map(struct irq_data *d)

 static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
 {
-	struct its_vlpi_map *map = get_vlpi_map(d);
 	irq_hw_number_t hwirq;
 	void *va;
 	u8 *cfg;

-	if (map) {
+	if (irqd_is_forwarded_to_vcpu(d)) {
+		struct its_vlpi_map *map = get_vlpi_map(d);
+
 		va = page_address(map->vm->vprop_page);
 		hwirq = map->vintid;

Shouldn't we fix get_vlpi_map() instead? Something like (untested):

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index e05673bcd52b..b704214390c0 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1170,13 +1170,14 @@ static void its_send_vclear(struct its_device *dev, u32 event_id)
  */
 static struct its_vlpi_map *get_vlpi_map(struct irq_data *d)
 {
-	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
-	u32 event = its_get_event_id(d);
+	if (irqd_is_forwarded_to_vcpu(d)) {
+		struct its_device *its_dev = irq_data_get_irq_chip_data(d);
+		u32 event = its_get_event_id(d);

-	if (!irqd_is_forwarded_to_vcpu(d))
-		return NULL;
+		return dev_event_to_vlpi_map(its_dev, event);
+	}

-	return dev_event_to_vlpi_map(its_dev, event);
+	return NULL;
 }

 static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)


Or am I missing the actual problem?

Overall, I'm starting to hate that ->parent hack as it's been the source
of a number of bugs.

The main issue is that the VPE hierarchy is missing one level (it has
no ITS domain, and goes directly from the VPE domain to the low-level
GIC domain). It means we end-up special-casing things, and that's never
good...

        M.
--
Jazz is not dead. It just smells funny...
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