Re: [PATCH] hw/intc/allwinner-a10-pic: Don't use set_bit()/clear_bit()

[Thomas Huth <thuth@redhat.com>]

On 24/04/2023 17.28, Peter Maydell wrote:
> The Allwinner PIC model uses set_bit() and clear_bit() to update the
> values in its irq_pending[] array when an interrupt arrives.  However
> it is using these functions wrongly: they work on an array of type
> 'long', and it is passing an array of type 'uint32_t'.  Because the
> code manually figures out the right array element, this works on
> little-endian hosts and on 32-bit big-endian hosts, where bits 0..31
> in a 'long' are in the same place as they are in a 'uint32_t'.
> However it breaks on 64-bit big-endian hosts.
> 
> Remove the use of set_bit() and clear_bit() in favour of using
> deposit32() on the array element.  This fixes a bug where on
> big-endian 64-bit hosts the guest kernel would hang early on in
> bootup.
> 
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   hw/intc/allwinner-a10-pic.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/intc/allwinner-a10-pic.c b/hw/intc/allwinner-a10-pic.c
> index 8cca1248073..4875e68ba6a 100644
> --- a/hw/intc/allwinner-a10-pic.c
> +++ b/hw/intc/allwinner-a10-pic.c
> @@ -49,12 +49,9 @@ static void aw_a10_pic_update(AwA10PICState *s)
>   static void aw_a10_pic_set_irq(void *opaque, int irq, int level)
>   {
>       AwA10PICState *s = opaque;
> +    uint32_t *pending_reg = &s->irq_pending[irq / 32];
>   
> -    if (level) {
> -        set_bit(irq % 32, (void *)&s->irq_pending[irq / 32]);
> -    } else {
> -        clear_bit(irq % 32, (void *)&s->irq_pending[irq / 32]);
> -    }
> +    *pending_reg = deposit32(*pending_reg, irq % 32, 1, level);
>       aw_a10_pic_update(s);
>   }
>   

Reviewed-by: Thomas Huth <thuth@redhat.com>