Xen devel - Jun 2013 - [PATCH] xen/arm: gic_shutdown_irq must only disable the right IRQ

When GICD_ICENABLERn is read, all the 1s bit represent enabled IRQs.
Currently gic_shutdown_irq:
    - read GICD_ICENABLER
    - set the corresping bit to 1
    - write back the new value
That means, Xen will disable more IRQs than necessary.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
---
 xen/arch/arm/gic.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 177560e..cafb681 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -117,12 +117,10 @@ static unsigned int gic_irq_startup(struct irq_desc *desc)
 
 static void gic_irq_shutdown(struct irq_desc *desc)
 {
-    uint32_t enabler;
     int irq = desc->irq;
 
     /* Disable routing */
-    enabler = GICD[GICD_ICENABLER + irq / 32];
-    GICD[GICD_ICENABLER + irq / 32] = enabler | (1u << (irq % 32));
+    GICD[GICD_ICENABLER + irq / 32] = (1u << (irq % 32));
 }
 
 static void gic_irq_enable(struct irq_desc *desc)
-- 
1.7.10.4

On Fri, 2013-06-28 at 12:25 +0100, Julien Grall wrote:
> When GICD_ICENABLERn is read, all the 1s bit represent enabled IRQs.
> Currently gic_shutdown_irq:
>     - read GICD_ICENABLER
>     - set the corresping bit to 1
>     - write back the new value
> That means, Xen will disable more IRQs than necessary.
> 
> Signed-off-by: Julien Grall <julien.grall@linaro.org>
Doh!

Acked-by: Ian Campbell <ian.campbell@citrix.com>
> ---
>  xen/arch/arm/gic.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> index 177560e..cafb681 100644
> --- a/xen/arch/arm/gic.c
> +++ b/xen/arch/arm/gic.c
> @@ -117,12 +117,10 @@ static unsigned int gic_irq_startup(struct irq_desc
*desc)
>  
>  static void gic_irq_shutdown(struct irq_desc *desc)
>  {
> -    uint32_t enabler;
>      int irq = desc->irq;
>  
>      /* Disable routing */
> -    enabler = GICD[GICD_ICENABLER + irq / 32];
> -    GICD[GICD_ICENABLER + irq / 32] = enabler | (1u << (irq % 32));
> +    GICD[GICD_ICENABLER + irq / 32] = (1u << (irq % 32));
>  }
>  
>  static void gic_irq_enable(struct irq_desc *desc)

On Fri, 28 Jun 2013, Julien Grall wrote:
> When GICD_ICENABLERn is read, all the 1s bit represent enabled IRQs.
> Currently gic_shutdown_irq:
>     - read GICD_ICENABLER
>     - set the corresping bit to 1
>     - write back the new value
> That means, Xen will disable more IRQs than necessary.
> 
> Signed-off-by: Julien Grall <julien.grall@linaro.org>
It''s impressive for how long we got this bug.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>  xen/arch/arm/gic.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> index 177560e..cafb681 100644
> --- a/xen/arch/arm/gic.c
> +++ b/xen/arch/arm/gic.c
> @@ -117,12 +117,10 @@ static unsigned int gic_irq_startup(struct irq_desc
*desc)
>  
>  static void gic_irq_shutdown(struct irq_desc *desc)
>  {
> -    uint32_t enabler;
>      int irq = desc->irq;
>  
>      /* Disable routing */
> -    enabler = GICD[GICD_ICENABLER + irq / 32];
> -    GICD[GICD_ICENABLER + irq / 32] = enabler | (1u << (irq % 32));
> +    GICD[GICD_ICENABLER + irq / 32] = (1u << (irq % 32));
>  }
>  
>  static void gic_irq_enable(struct irq_desc *desc)
> -- 
> 1.7.10.4
>

On Fri, 2013-06-28 at 12:32 +0100, Stefano Stabellini
wrote:
> On Fri, 28 Jun 2013, Julien Grall wrote:
> > When GICD_ICENABLERn is read, all the 1s bit represent enabled IRQs.
> > Currently gic_shutdown_irq:
> >     - read GICD_ICENABLER
> >     - set the corresping bit to 1
> >     - write back the new value
> > That means, Xen will disable more IRQs than necessary.
> > 
> > Signed-off-by: Julien Grall <julien.grall@linaro.org>
> 
> It''s impressive for how long we got this bug.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
I think you meant Acked-by, so applied with both our acks.