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

[Sascha Bischoff <sascha.bischoff@arm.com>]

On 02/11/2026 14:46, Lorenzo Pieralisi wrote:
> 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>
> 

I've reworked this a bit to make it clearer. Hence, I've left off your 
Acked-by tag on v2. I hope that's OK!

Thanks,
Sascha

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