Re: [PATCH] drm/amdgpu: Fix validating flush_gpu_tlb_pasid()

["Timur Kristóf" <timur.kristof@gmail.com>]

On Monday, January 19, 2026 11:12:02 AM Central European Standard Time 
Christian König wrote:
> On 1/18/26 13:57, Timur Kristóf wrote:
> > When a function holds a lock and we return without unlocking it,
> > it deadlocks the kernel. We should always unlock before returning.
> > 
> > This commit fixes suspend/resume on SI.
> > Tested on two Tahiti GPUs: FirePro W9000 and R9 280X.
> > 
> > Fixes: bc2dea30038a ("drm/amdgpu: validate the flush_gpu_tlb_pasid()")
> > Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
> > ---
> > 
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c index
> > 0e67fa4338ff..4fa24be1bf45 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> > @@ -769,7 +769,7 @@ int amdgpu_gmc_flush_gpu_tlb_pasid(struct
> > amdgpu_device *adev, uint16_t pasid,> 
> >  	struct amdgpu_ring *ring = &adev->gfx.kiq[inst].ring;
> >  	struct amdgpu_kiq *kiq = &adev->gfx.kiq[inst];
> >  	unsigned int ndw;
> > 
> > -	int r, cnt = 0;
> > +	int r = 0, cnt = 0;
> 
> Please don't initialize return values in the declaration, that is usually
> considered bad coding style.

The initialization is necessary, otherwise the function will return an 
uninitialized value when flush_gpu_tlb_pasid==NULL

> >  	uint32_t seq;
> >  	
> >  	/*
> > 
> > @@ -782,7 +782,7 @@ int amdgpu_gmc_flush_gpu_tlb_pasid(struct
> > amdgpu_device *adev, uint16_t pasid,> 
> >  	if (!adev->gmc.flush_pasid_uses_kiq || !ring->sched.ready) {
> >  	
> >  		if (!adev->gmc.gmc_funcs->flush_gpu_tlb_pasid)
> > 
> > -			return 0;
> > +			goto error_unlock_reset;
> 
> Ah, yes good catch!
> 
> With the change to r initialization dropped: Reviewed-by: Christian König
> <christian.koenig@amd.com>

If I drop it, then it will regress again because it returns an uninitialized 
value.

> 
> Regards,
> Christian.
> 
> >  		if (adev->gmc.flush_tlb_needs_extra_type_2)
> >  		
> >  			adev->gmc.gmc_funcs-
>flush_gpu_tlb_pasid(adev, pasid,
> > 
> > @@ -797,7 +797,6 @@ int amdgpu_gmc_flush_gpu_tlb_pasid(struct
> > amdgpu_device *adev, uint16_t pasid,> 
> >  		adev->gmc.gmc_funcs->flush_gpu_tlb_pasid(adev, pasid,
> >  		
> >  							 
flush_type, all_hub,
> >  							 
inst);
> > 
> > -		r = 0;
> > 
> >  	} else {
> >  	
> >  		/* 2 dwords flush + 8 dwords fence */
> >  		ndw = kiq->pmf->invalidate_tlbs_size + 8;