linux-kernel - Re: [PATCH 6/7] drm/amdgpu: Ensure kunmap is called on error

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Message-ID: <20211214033725.GR3538886@iweiny-DESK2.sc.intel.com>
Date:   Mon, 13 Dec 2021 19:37:25 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Christian König <christian.koenig@....com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        linux-arm-msm@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        amd-gfx@...ts.freedesktop.org
Subject: Re: [PATCH 6/7] drm/amdgpu: Ensure kunmap is called on error

On Mon, Dec 13, 2021 at 09:37:32PM +0100, Christian König wrote:
> Am 11.12.21 um 00:24 schrieb ira.weiny@...el.com:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > The default case leaves the buffer object mapped in error.
> > 
> > Add amdgpu_bo_kunmap() to that case to ensure the mapping is cleaned up.
> 
> Mhm, good catch. But why do you want to do this in the first place?

I'm not sure I understand the question.

Any mapping of memory should be paired with an unmapping when no longer needed.
And this is supported by the call to amdgpu_bo_kunmap() in the other
non-default cases.

Do you believe the mapping is not needed?

Ira

> 
> Christian.
> 
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > 
> > ---
> > NOTE: It seems like this function could use a fair bit of refactoring
> > but this is the easiest way to fix the actual bug.
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c | 1 +
> >   1 file changed, 1 insertion(+)
> > nice
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c
> > index 6f8de11a17f1..b3ffd0f6b35f 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c
> > @@ -889,6 +889,7 @@ static int amdgpu_uvd_cs_msg(struct amdgpu_uvd_cs_ctx *ctx,
> >   		return 0;
> >   	default:
> > +		amdgpu_bo_kunmap(bo);
> >   		DRM_ERROR("Illegal UVD message type (%d)!\n", msg_type);
> >   	}
>