Re: [Qemu-devel] [PATCH 02/10] cuda: don't allow writes to port output pins

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

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On 02/03/2018 07:37 AM, Mark Cave-Ayland wrote:
> Use the direction registers as a mask to ensure that only input pins are
> updated upon write.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  hw/misc/macio/cuda.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/misc/macio/cuda.c b/hw/misc/macio/cuda.c
> index 23b7e0f5b0..7214e7adcb 100644
> --- a/hw/misc/macio/cuda.c
> +++ b/hw/misc/macio/cuda.c
> @@ -359,11 +359,11 @@ static void cuda_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
>  
>      switch(addr) {
>      case CUDA_REG_B:
> -        s->b = val;
> +        s->b = (s->b & ~s->dirb) | (val & s->dirb);

I personally find it easier to read in 2 lines (&=~, |=)

It might be useful to log invalid guest values:

           if (val & ~s->dirb) {
               GUEST_ERROR();
               val &= s->dirb;
           }
           s->b |= val;

>          cuda_update(s);
>          break;
>      case CUDA_REG_A:
> -        s->a = val;
> +        s->a = (s->a & ~s->dira) | (val & s->dira);

Ditto.

Regardless:
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

>          break;
>      case CUDA_REG_DIRB:
>          s->dirb = val;
> 


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