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

Marc Zyngier
2020-01-22T10:44:10Z

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@huawei.com>
> ---
>
> 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...