Patch "drm/amdgpu: avoid integer overflow warning in amdgpu_device_resize_fb_bar()" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/amdgpu: avoid integer overflow warning in amdgpu_device_resize_fb_bar()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-amdgpu-avoid-integer-overflow-warning-in-amdgpu_.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b3398aef9db225de6c2415d30fa9923da8dec07f
Author: Arnd Bergmann <arnd@xxxxxxxx>
Date:   Fri Jul 7 13:11:51 2023 +0200

    drm/amdgpu: avoid integer overflow warning in amdgpu_device_resize_fb_bar()
    
    [ Upstream commit 822130b5e8834ab30ad410cf19a582e5014b9a85 ]
    
    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)
                        ~~~~~~~~~~ ^ ~~~~~~~~~~~~~~
    
    As gcc does not warn about this in dead code, add an IS_ENABLED() check at
    the start of the function. This will always return success but not actually resize
    the BAR on 32-bit architectures without high memory, which is exactly what
    we want here, as the driver can fall back to bank switching the VRAM
    access.
    
    Fixes: 31b8adab3247 ("drm/amdgpu: require a root bus window above 4GB for BAR resize")
    Reviewed-by: Christian König <christian.koenig@xxxxxxx>
    Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
    Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index d0e1fd011de54..e5032eb9ae291 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -759,6 +759,9 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 	u16 cmd;
 	int r;
 
+	if (!IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
+		return 0;
+
 	/* Bypass for VF */
 	if (amdgpu_sriov_vf(adev))
 		return 0;