Re: [PATCH] drm/amdgpu:Check gfx poweron when skip flush_gpu_tlb

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 09.10.23 um 03:50 schrieb Xu, Feifei:
> [AMD Official Use Only - General]
>
> Hi,
>
>>> Based on your description, the above code should use "||" instead of "&&",
> && is to add more restriction here.  To avoid skipping necessary TLB flush by return.
> For Asics < GFX11, !adev->gfx.is_poweron is always true (this paremeter is intrudoced from GFX11), only depends on reset_domain->sem;
> For Asics = GFX11, !adev->gfx.is_poweron might be false (which gfx might already poweron in the reset), this will make the if () not ture, return will not be executed, thus flush TLB.

First of all the patch is broken because you only handle the locking, 
but not the unlocking part.

Then a TLB flush shouldn't be necessary on reset. A reset implies that 
the TLB is cleared as well.

We discussed the possibility to avoid that, but this is not supposed to 
be happening at the moment.

Regards,
Christian.

>
>>> And after merging code into one line may result in the lock not being released if the lock can be acquired success.
> If !adev->gfx.is_poweron is true, the reset_domin->sem will not be down_read_trylock, thus could avoid this deadlock.

>
> Thanks,
> Feifei
>
> -----Original Message-----
> From: Wang, Yang(Kevin) <KevinYang.Wang@amd.com>
> Sent: Sunday, October 8, 2023 9:36 PM
> To: Xu, Feifei <Feifei.Xu@amd.com>; amd-gfx@lists.freedesktop.org
> Cc: Xu, Feifei <Feifei.Xu@amd.com>; Xu, Feifei <Feifei.Xu@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Zhang, Hawking <Hawking.Zhang@amd.com>
> Subject: RE: [PATCH] drm/amdgpu:Check gfx poweron when skip flush_gpu_tlb
>
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Feifei Xu
> Sent: Sunday, October 8, 2023 6:07 PM
> To: amd-gfx@lists.freedesktop.org
> Cc: Xu, Feifei <Feifei.Xu@amd.com>; Xu, Feifei <Feifei.Xu@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Zhang, Hawking <Hawking.Zhang@amd.com>
> Subject: [PATCH] drm/amdgpu:Check gfx poweron when skip flush_gpu_tlb
>
> To fix the gpu recovery failed on GFX11 with gfxhub pagefault, flush gpu tlb after reset on GFX11.
> Gfxhub tlb flush need check if adev->gfx.is_poweron set.
>
> Fixes: d0c860f33553 ("drm/amdgpu: rework lock handling for flush_tlb v2")
>
> Signed-off-by: Feifei Xu <Feifei.Xu@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> index 2f9bb86edd71..048d32edee88 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> @@ -611,8 +611,9 @@ void amdgpu_gmc_flush_gpu_tlb(struct amdgpu_device *adev, uint32_t vmid,
>                  /*
>                   * A GPU reset should flush all TLBs anyway, so no need to do
>                   * this while one is ongoing.
> +                * For GFX11, gfxhub flush check if adev->gfx.is_poweron is set.
>                   */
> -               if (!down_read_trylock(&adev->reset_domain->sem))
> +               if (!down_read_trylock(&adev->reset_domain->sem) &&
> +!adev->gfx.is_poweron)
>                          return;
>
> [Kevin]:
> Based on your description, the above code should use "||" instead of "&&",
> And after merging code into one line may result in the lock not being released if the lock can be acquired success.
>
> Best Regards,
> Kevin
>
>                  if (adev->gmc.flush_tlb_needs_extra_type_2)
> --
> 2.34.1
>