Re: [PATCH 09/10] irqchip/gic-v5: Clean the allocated linear device table size

[Lorenzo Pieralisi <lpieralisi@kernel.org>]

On Mon, Nov 02, 2026 at 01:33:02PM +0000, Sascha Bischoff wrote:
> When the linear device table exceeds the kmalloc limit, the driver
> caps the DeviceID width before allocation but keeps the original size
> for cache maintenance. On a noncoherent ITS, this cleans beyond the
> allocated table.
> 
> Recalculate the size after capping the DeviceID width.
> 
> Fixes: 57d72196dfc85 ("irqchip/gic-v5: Add GICv5 ITS support")
> Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
> ---
>  drivers/irqchip/irq-gic-v5-its.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v5-its.c b/drivers/irqchip/irq-gic-v5-its.c
> index 4de07bbdc4923..c0f3982229194 100644
> --- a/drivers/irqchip/irq-gic-v5-its.c
> +++ b/drivers/irqchip/irq-gic-v5-its.c
> @@ -601,6 +601,7 @@ static int gicv5_its_alloc_devtab_linear(struct gicv5_its_chip_data *its,
>  		pr_warn("Limiting device ID bits from %u to %u\n",
>  			device_id_bits, device_id_cap);
>  		device_id_bits = device_id_cap;
> +		sz = BIT_ULL(device_id_bits) * sizeof(*devtab);
>  	}
>  

Or sz = KMALLOC_MAX_SIZE;

that's what we are doing after all.

I wonder whether moving:

sz = BIT_ULL(device_id_bits) * sizeof(*devtab);

after the capping out of the if and do:

if (BIT_ULL(device_id_bits) * sizeof(*devtab) > KMALLOC_MAX_SIZE)

to check whether mem alloc should be capped makes this any easier
to read.

Regardless, this patch is a fix and it is right to make it as small
as possible:

Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>

>  	devtab = kcalloc(BIT(device_id_bits), sizeof(*devtab), GFP_KERNEL);
> 
> -- 
> 2.34.1
>