linux-kernel - Re: [PATCH] irqchip/gic-v3-its: Don't confuse get_vlpi

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Date:   Wed, 22 Jan 2020 10:44:06 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Zenghui Yu <yuzenghui@...wei.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jason@...edaemon.net,
        wanghaibin.wang@...wei.com
Subject: Re: [PATCH] irqchip/gic-v3-its: Don't confuse get_vlpi_map() by
 writing DB config

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@...wei.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...