[PATCH] irqchip: gicv3-its: fix ITS CPU init

[Marc Zyngier]

Hi Vladimir,

On 09/01/15 15:50, Vladimir Murzin wrote:
> We skip initialisation of ITS in case the device-tree has no
> corresponding description, but we are still accessing to ITS bits while
> setting CPU interface what leads to the kernel panic:
> 
> ITS: No ITS available, not enabling LPIs
> CPU0: found redistributor 0 region 0:0x000000002f100000
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> pgd = ffffffc0007fb000
> [00000000] *pgd=00000000fc407003, *pud=00000000fc407003, *pmd=00000000fc408003, *pte=006000002f000707
> Internal error: Oops: 96000005 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.19.0-rc2+ #318
> Hardware name: FVP Base (DT)
> task: ffffffc00077edb0 ti: ffffffc00076c000 task.ti: ffffffc00076c000
> PC is at its_cpu_init+0x2c/0x320
> LR is at gic_cpu_init+0x168/0x1bc
> 
> It happens in gic_rdists_supports_plpis() because gic_rdists is NULL.
> The gic_rdists is set to non-NULL only when ITS node is presented in
> the device-tree.
> 
> Fix this by moving the call to gic_rdists_supports_plpis() inside the
> !list_empty(&its_nodes) block, because it is that list that guards the
> validity of the rest of the information in this driver.
> 
> Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>

Looks good to me.

Acked-by: Marc Zyngier <marc.zyngier at arm.com>

	M.

> ---
>  drivers/irqchip/irq-gic-v3-its.c |    9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 86e4684..128a12b 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1382,12 +1382,11 @@ static bool gic_rdists_supports_plpis(void)
>  
>  int its_cpu_init(void)
>  {
> -	if (!gic_rdists_supports_plpis()) {
> -		pr_info("CPU%d: LPIs not supported\n", smp_processor_id());
> -		return -ENXIO;
> -	}
> -
>  	if (!list_empty(&its_nodes)) {
> +		if (!gic_rdists_supports_plpis()) {
> +			pr_info("CPU%d: LPIs not supported\n", smp_processor_id());
> +			return -ENXIO;
> +		}
>  		its_cpu_init_lpis();
>  		its_cpu_init_collection();
>  	}
> 


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