Re: [PATCH] drm/amdgpu: avoid integer overflow warning in amdgpu_device_resize_fb_bar()

["Christian König" <christian.koenig@amd.com>]

Am 03.07.23 um 14:35 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd@arndb.de>
>
> On 32-bit architectures comparing a resource against a value larger than
> U32_MAX can cause a warning:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:1344:18: error: result of comparison of constant 4294967296 with expression of type 'resource_size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>                      res->start > 0x100000000ull)
>                      ~~~~~~~~~~ ^ ~~~~~~~~~~~~~~
>
> The compiler is right that this cannot happen in this configuration, which
> is ok, so just add a cast to shut up the warning.

Well it doesn't make sense to compile that driver on systems with only 
32bit phys_addr_t in the first place.

It might be cleaner to just not build the whole driver on such systems 
or at least leave out this function.

Regards,
Christian

>
> Fixes: 31b8adab3247e ("drm/amdgpu: require a root bus window above 4GB for BAR resize")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 7f069e1731fee..abd13942aac5d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -1341,7 +1341,7 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
>   
>   	pci_bus_for_each_resource(root, res, i) {
>   		if (res && res->flags & (IORESOURCE_MEM | IORESOURCE_MEM_64) &&
> -		    res->start > 0x100000000ull)
> +		    (u64)res->start > 0x100000000ull)
>   			break;
>   	}
>