Re: [PATCH] drm/amdgpu: skip pci_restore_state under sriov during device init

["Lazar, Lijo" <lijo.lazar@amd.com>]

On 10/24/2024 11:19 AM, Victor Zhao wrote:
> during device init, under sriov, pci_restore_state happens after
> fullaccess released, and it can have race condition with mmio protection
> enable from host side.
> 
> Since msix was toggled during pci_restore_state, if mmio protection
> happens during this time, guest side msix will not be properly
> programmed and leading to missing interrupts.
> 
> So skip pci_restore_state during device init.
> 
> Signed-off-by: Victor Zhao <Victor.Zhao@amd.com>
> ---
>  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 6c0ff1c2ae4c..52803cd91ef5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4524,7 +4524,7 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>  		dev_err(adev->dev, "amdgpu_pmu_init failed\n");
>  
>  	/* Have stored pci confspace at hand for restore in sudden PCI error */
> -	if (amdgpu_device_cache_pci_state(adev->pdev))
> +	if (!amdgpu_sriov_vf(adev) && amdgpu_device_cache_pci_state(adev->pdev))

This also prevents caching the state. If the intention is that way, put
the check inside amdgpu_device_cache_pci_state to make it explicit that
VFs avoid caching config space.

Thanks,
Lijo

>  		pci_restore_state(pdev);
>  
>  	/* if we have > 1 VGA cards, then disable the amdgpu VGA resources */