[PATCH] irqchip/gic-v3: Ensure change to DS is visible

[PATCH] irqchip/gic-v3: Ensure change to DS is visible

[Vladimir Murzin]

Sashiko reported missing GIC synchronization when the
FLAGS_WORKAROUND_INSECURE path modifies DS. Specifically, an immediate
read of the DS state after the write might not observe the effect of
that write, which can lead to misreporting the DS state.

Updates to the DS bit are tracked by RWP, so poll it after the write
before proceeding to read back the DS state.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 drivers/irqchip/irq-gic-v3.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 6e1fa5b247fc..181f6eb11732 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -164,6 +164,7 @@ static inline bool gic_dist_security_disabled(void)
 
 static bool cpus_have_security_disabled __ro_after_init;
 static bool cpus_have_group0 __ro_after_init;
+static void gic_dist_wait_for_rwp(void);
 
 static void __init gic_prio_init(void)
 {
@@ -179,6 +180,7 @@ static void __init gic_prio_init(void)
 			val = readl_relaxed(gic_data.dist_base + GICD_CTLR);
 			val |= GICD_CTLR_DS;
 			writel_relaxed(val, gic_data.dist_base + GICD_CTLR);
+			gic_dist_wait_for_rwp();
 
 			ds = gic_dist_security_disabled();
 			if (ds)
-- 
2.34.1

Re: [PATCH] irqchip/gic-v3: Ensure change to DS is visible

[Marc Zyngier]

On Wed, 30 Sep 2026 17:11:23 +0100,
Vladimir Murzin <vladimir.murzin@arm.com> wrote:
> 
> Sashiko reported missing GIC synchronization when the
> FLAGS_WORKAROUND_INSECURE path modifies DS. Specifically, an immediate
> read of the DS state after the write might not observe the effect of
> that write, which can lead to misreporting the DS state.
> 
> Updates to the DS bit are tracked by RWP, so poll it after the write
> before proceeding to read back the DS state.
> 
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 6e1fa5b247fc..181f6eb11732 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -164,6 +164,7 @@ static inline bool gic_dist_security_disabled(void)
>  
>  static bool cpus_have_security_disabled __ro_after_init;
>  static bool cpus_have_group0 __ro_after_init;
> +static void gic_dist_wait_for_rwp(void);
>  
>  static void __init gic_prio_init(void)
>  {
> @@ -179,6 +180,7 @@ static void __init gic_prio_init(void)
>  			val = readl_relaxed(gic_data.dist_base + GICD_CTLR);
>  			val |= GICD_CTLR_DS;
>  			writel_relaxed(val, gic_data.dist_base + GICD_CTLR);
> +			gic_dist_wait_for_rwp();
>  
>  			ds = gic_dist_security_disabled();
>  			if (ds)

Ah, well spotted. FWIW:

Reviewed-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Jazz isn't dead. It just smells funny.