[PATCH] drm/amd: fix debugfs access for discovery blob

[Alex Deucher]

On Tue, Aug 1, 2023 at 4:15 PM Mario Limonciello
<mario.limonciello at amd.com> wrote:
>
> Accessing the blob for amdgpu discovery from debugfs triggers:
>
> [ 1924.487667] kernel BUG at mm/usercopy.c:102!
>
> usercopy_abort() explains that it needs to be solved by creating
> a cache to store the data.
>
> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2748#note_2023519
> Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  7 +++++--
>  drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 17 ++++++++++++++++-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c     |  2 ++
>  3 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index a3b86b86dc477..66a2251bdeba4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -791,8 +791,11 @@ struct amdgpu_device {
>         bool                            accel_working;
>         struct notifier_block           acpi_nb;
>         struct amdgpu_i2c_chan          *i2c_bus[AMDGPU_MAX_I2C_BUS];
> -       struct debugfs_blob_wrapper     debugfs_vbios_blob;
> -       struct debugfs_blob_wrapper     debugfs_discovery_blob;
> +#if defined(CONFIG_DEBUG_FS)
> +       struct debugfs_blob_wrapper     debugfs_vbios_blob;
> +       struct debugfs_blob_wrapper     debugfs_discovery_blob;
> +       struct kmem_cache               *discovery_blob_cache;
> +#endif
>         struct mutex                    srbm_mutex;
>         /* GRBM index mutex. Protects concurrent access to GRBM index */
>         struct mutex                    grbm_idx_mutex;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index 56e89e76ff179..55ea5be14b188 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -2180,7 +2180,15 @@ int amdgpu_debugfs_init(struct amdgpu_device *adev)
>         debugfs_create_blob("amdgpu_vbios", 0444, root,
>                             &adev->debugfs_vbios_blob);
>
> -       adev->debugfs_discovery_blob.data = adev->mman.discovery_bin;
> +
> +       adev->discovery_blob_cache = kmem_cache_create_usercopy("amdgpu_discovery",
> +                                                               adev->mman.discovery_tmr_size,
> +                                                               0, 0, 0,
> +                                                               adev->mman.discovery_tmr_size,
> +                                                               NULL);
> +       adev->debugfs_discovery_blob.data = kmem_cache_alloc(adev->discovery_blob_cache, GFP_KERNEL);
> +       memcpy(adev->debugfs_discovery_blob.data, adev->mman.discovery_bin,
> +              adev->mman.discovery_tmr_size);
>         adev->debugfs_discovery_blob.size = adev->mman.discovery_tmr_size;
>         debugfs_create_blob("amdgpu_discovery", 0444, root,
>                             &adev->debugfs_discovery_blob);
> @@ -2188,6 +2196,12 @@ int amdgpu_debugfs_init(struct amdgpu_device *adev)
>         return 0;
>  }
>
> +void amdgpu_debugfs_fini(struct amdgpu_device *adev)
> +{
> +       kmem_cache_free(adev->discovery_blob_cache, adev->debugfs_discovery_blob.data);
> +       kmem_cache_destroy(adev->discovery_blob_cache);
> +}
> +
>  #else
>  int amdgpu_debugfs_init(struct amdgpu_device *adev)
>  {
> @@ -2197,4 +2211,5 @@ int amdgpu_debugfs_regs_init(struct amdgpu_device *adev)
>  {
>         return 0;
>  }
> +inline void amdgpu_debugfs_fini(struct amdgpu_device *adev) {}
>  #endif
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 0593ef8fe0a63..1a3b30dff5171 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -2276,6 +2276,8 @@ amdgpu_pci_remove(struct pci_dev *pdev)
>         struct drm_device *dev = pci_get_drvdata(pdev);
>         struct amdgpu_device *adev = drm_to_adev(dev);
>
> +       amdgpu_debugfs_fini(adev);
> +
>         amdgpu_xcp_dev_unplug(adev);
>         drm_dev_unplug(dev);
>
> --
> 2.34.1
>