linux-kernel - Re: [PATCH] drm/amdgpu: Fix shift type in amdgpu_debugfs_sdma_sched_mask

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Message-ID: <4372d931-865f-4b91-8122-fa5cd1b554f2@amd.com>
Date: Wed, 8 Jan 2025 12:39:38 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Dan Carpenter <dan.carpenter@...aro.org>,
 Jesse Zhang <jesse.zhang@....com>
Cc: Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 Xinhui Pan <Xinhui.Pan@....com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Hawking Zhang <Hawking.Zhang@....com>,
 Tim Huang <tim.huang@....com>, Likun Gao <Likun.Gao@....com>,
 Yang Wang <kevinyang.wang@....com>, Le Ma <le.ma@....com>,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] drm/amdgpu: Fix shift type in
 amdgpu_debugfs_sdma_sched_mask_set()

On 1/8/2025 03:41, Dan Carpenter wrote:
> The "mask" and "val" variables are type u64.  The problem is that the
> BIT() macros are type unsigned long which is just 32 bits on 32bit
> systems.
> 
> It's unlikely that people will be using this driver on 32bit kernels
> and even if they did we only use the lower AMDGPU_MAX_SDMA_INSTANCES (16)
> bits.  So this bug does not affect anything in real life.
> 
> Still, for correctness sake, u64 bit masks should use BIT_ULL().
> 
> Fixes: d2e3961ae371 ("drm/amdgpu: add amdgpu_sdma_sched_mask debugfs")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---

Applied, thanks!

>   drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c
> index 632295bf3875..174badca27e7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c
> @@ -362,13 +362,13 @@ static int amdgpu_debugfs_sdma_sched_mask_set(void *data, u64 val)
>   	if (!adev)
>   		return -ENODEV;
>   
> -	mask = (1 << adev->sdma.num_instances) - 1;
> +	mask = BIT_ULL(adev->sdma.num_instances) - 1;
>   	if ((val & mask) == 0)
>   		return -EINVAL;
>   
>   	for (i = 0; i < adev->sdma.num_instances; ++i) {
>   		ring = &adev->sdma.instance[i].ring;
> -		if (val & (1 << i))
> +		if (val & BIT_ULL(i))
>   			ring->sched.ready = true;
>   		else
>   			ring->sched.ready = false;