Re: [PATCH 16/26] hw/display/apple-gfx: Asynchronous MMIO writes on x86-64

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Phil,

On 15/7/24 23:06, Phil Dennis-Jordan wrote:
> This change ensures that the MMIO write calls into the PVG
> framework are performed asynchronously on a background dispatch
> queue. Without this, we rapidly run into re-entrant MMIO issues.
> 
> This problem only seems to exist on x86-64 hosts. Conversely,
> doing it async on arm64/vmapple causes other issues,

Such as?

> so we're
> left with 2 different implementations.
> 
> Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
> ---
>   hw/display/apple-gfx.m | 15 ++++++++++++++-
>   1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/display/apple-gfx.m b/hw/display/apple-gfx.m
> index 806feb58fa..48463e5a1f 100644
> --- a/hw/display/apple-gfx.m
> +++ b/hw/display/apple-gfx.m
> @@ -67,15 +67,28 @@ static uint64_t apple_gfx_read(void *opaque, hwaddr offset, unsigned size)
>       return res;
>   }
>   
> -static void apple_gfx_write(void *opaque, hwaddr offset, uint64_t val, unsigned size)
> +static void apple_gfx_write(void *opaque, hwaddr offset, uint64_t val,
> +                            unsigned size)
>   {
>       AppleGFXState *s = opaque;
>   
>       trace_apple_gfx_write(offset, val);
>   
> +#ifdef __x86_64__
> +    id<PGDevice> dev = s->pgdev;
> +    dispatch_queue_t bg_queue = NULL;
> +
> +    bg_queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);
> +    [dev retain];
> +    dispatch_async(bg_queue, ^{
> +        [dev mmioWriteAtOffset:offset value:val];
> +        [dev release];
> +    });
> +#else
>       bql_unlock();
>       [s->pgdev mmioWriteAtOffset:offset value:val];
>       bql_lock();
> +#endif
>   }
>   
>   static const MemoryRegionOps apple_gfx_ops = {