[Intel-gfx] [PATCH] sna/kgem: Gen8 blt broken when dest base offset has bit 4 set

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> On Wed, Nov 19, 2014 at 03:10:05PM +0200, Mika Kuoppala wrote:
>> With bit 4 set in destination base address, the Gen8 blitter
>> fails and blits errorneously into area before destination
>> (dest - 16 bytes), corrupting memory.
>> 
>> Broken hw is suspect.
>> 
>> v2: Update the destination base offset pattern as revealed
>>     by igt/tests/gem_userptr_blits/destination-bo-align
>> 
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79053
>> Cc: Chris Wilson <chris at chris-wilson.co.uk>
>> Tested-by: xunx.fang at intel.com
>> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
>> ---
>>  src/sna/kgem.h | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/src/sna/kgem.h b/src/sna/kgem.h
>> index 6adae3b..344dcea 100644
>> --- a/src/sna/kgem.h
>> +++ b/src/sna/kgem.h
>> @@ -551,6 +551,11 @@ static inline bool kgem_bo_blt_pitch_is_ok(struct kgem *kgem,
>>  					   struct kgem_bo *bo)
>>  {
>>  	int pitch = bo->pitch;
>> +
>> +	/* bdw is broken with blit dst align */
>> +	if (kgem->gen >= 0100 && pitch & (1 << 4))
>> +		return false;
>> +
>>  	if (kgem->gen >= 040 && bo->tiling)
>>  		pitch /= 4;
>>  	if (pitch > MAXSHORT) {
>
> I added a chunk:
>
> @@ -573,6 +580,12 @@ static inline bool kgem_bo_can_blt(struct kgem *kgem,
>                 return false;
>         }
>  
> +       if (kgem->gen >= 0100 && bo->proxy && bo->delta & (1 << 4)) {
> +               DBG(("%s: can not blt to handle=%d, delta=%d\n",
> +                    __FUNCTION__, bo->handle, bo->delta));
> +               return false;
> +       }
> +
>         return kgem_bo_blt_pitch_is_ok(kgem, bo);
>  }
>
> In case we had a 32-byte pitch but starting at a 16-byte offset, which
> should also trigger the corruption, right?
> -Chris

So far the story is:

in XY_SRC_COPY_BLT, if Destination base address
bit 4 is set, it will blit into wrong destination

If bit 4 is set in Source base address, you
get blit into correct spot but with bad data.

I have used 4 * 4 dwords as a pattern. I will
do more experiments with the pitch tomorrow.

-Mika

>
> -- 
> Chris Wilson, Intel Open Source Technology Centre