[PATCH 5.15 069/779] drm/amdgpu: fix check in fbdev init

[Greg Kroah-Hartman]

From: Alex Deucher <alexander.deucher@xxxxxxx>

The new vkms virtual display code is atomic so there is
no need to call drm_helper_disable_unused_functions()
when it is enabled.  Doing so can result in a segfault.
When the driver switched from the old virtual display code
to the new atomic virtual display code, it was missed that
we enable virtual display unconditionally under SR-IOV
so the checks here missed that case.  Add the missing
check for SR-IOV.

There is no equivalent of this patch for Linus' tree
because the relevant code no longer exists.  This patch
is only relevant to kernels 5.15 and 5.16.

Fixes: 84ec374bd580 ("drm/amdgpu: create amdgpu_vkms (v4)")
Cc: stable@xxxxxxxxxxxxxxx # 5.15.x
Cc: hgoffin@xxxxxxxxxx
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
@@ -341,7 +341,8 @@ int amdgpu_fbdev_init(struct amdgpu_devi
 	}
 
 	/* disable all the possible outputs/crtcs before entering KMS mode */
-	if (!amdgpu_device_has_dc_support(adev) && !amdgpu_virtual_display)
+	if (!amdgpu_device_has_dc_support(adev) && !amdgpu_virtual_display &&
+	    !amdgpu_sriov_vf(adev))
 		drm_helper_disable_unused_functions(adev_to_drm(adev));
 
 	drm_fb_helper_initial_config(&rfbdev->helper, bpp_sel);