[PATCH v2] drm/amdgpu: Inform if PCIe based P2P links are not available

[Felix Kuehling]

On 2024-11-05 20:19, Ramesh Errabolu wrote:
> Raise an info message in kernel log if PCIe root complex
> determines that a AMD GPU device D<i> cannot have P2P
> communication with another AMD GPU device D<j>
> 
> Signed-off-by: Ramesh Errabolu <Ramesh.Errabolu at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 230c24638a34..ab304a2c4aaf 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -6222,6 +6222,8 @@ bool amdgpu_device_is_peer_accessible(struct amdgpu_device *adev,
>  	bool p2p_access =
>  		!adev->gmc.xgmi.connected_to_cpu &&
>  		!(pci_p2pdma_distance(adev->pdev, peer_adev->dev, false) < 0);
> +	if (!p2p_access)
> +		pr_info("PCIe based P2P links are not available\n");

This message would be a lot more useful if it told you, which two devices are affected. You can use dev_info to have it print the PCIe BDF of adev. Then you only need to print additional information for peer_adev using pci_name(peer_adev->pdev).

Alternatively, you can just set the last parameter of pci_p2pdma_distance to "true". Although, that will produce more scary-looking warning messages. I believe Lijo disabled that at some point because of that reason.

Regards,
  Felix



>  
>  	bool is_large_bar = adev->gmc.visible_vram_size &&
>  		adev->gmc.real_vram_size == adev->gmc.visible_vram_size;