Re: drm/amdgpu: apply AMDGPU_IB_FLAG_EMIT_MEM_SYNC to compute IBs too

["Deucher, Alexander" <Alexander.Deucher@xxxxxxx>]

[AMD Official Use Only - Internal Distribution Only]

Do we have open source code UMD code which uses this?

Alex

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From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
Sent: Sunday, April 26, 2020 4:55 AM
To: Marek Olšák <maraeo@xxxxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>
Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; amd-gfx mailing list <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: drm/amdgpu: apply AMDGPU_IB_FLAG_EMIT_MEM_SYNC to compute IBs too

 

Thanks for that explanation. I suspected that there was a good reason to have that in the kernel, but couldn't find one.

In this case the patch is Reviewed-by: Christian König <christian.koenig@xxxxxxx>

We should probably add this explanation as comment to the flag as well.

Thanks,
Christian.

Am 26.04.20 um 02:43 schrieb Marek Olšák:

It was merged into amd-staging-drm-next.

I'm not absolutely sure, but I think we need to invalidate before IBs if an IB is cached in L2 and the CPU has updated it. It can only be cached in L2 if something other than CP has read it or written to it without invalidation. CP reads don't cache it but they can hit the cache if it's already cached.

For CE, we need to invalidate before the IB in the kernel, because CE IBs can't do cache invalidations IIRC. This is the number one reason for merging the already pushed commits.

Marek

On Sat., Apr. 25, 2020, 11:03 Christian König, <ckoenig.leichtzumerken@xxxxxxxxx> wrote:

Was that patch set actually merged upstream? My last status is that we couldn't find a reason why we need to do this in the kernel.

Christian.

Am 25.04.20 um 10:52 schrieb Marek Olšák:

This was missed.

Marek

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