Re: [PATCH] drm: nova: Move VRAM BAR size query to GPU info

[Alistair Popple <apopple@nvidia.com>]

On 2026-09-28 at 00:22 +1000, Danilo Krummrich <dakr@kernel.org> wrote...
> Nova exposes static information via its DRM_IOCTL_NOVA_INFO ioctl, thus
> add vram_bar_size to struct drm_nova_info_gpu and remove
> DRM_IOCTL_NOVA_GETPARAM and its uAPI definitions.

I see everyone else has already jumped on this but feel free to add my RB as
well:

Reviewed-by: Alistair Popple <apopple@nvidia.com>

> This breaks the uAPI, which is still fine at this point. It requires the
> corresponding drm-test change in [1].
> 
> Link: https://gitlab.freedesktop.org/dakr/drm-test/-/merge_requests/2 [1]
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  drivers/gpu/drm/nova/driver.rs |  3 +--
>  drivers/gpu/drm/nova/file.rs   | 18 +----------------
>  include/uapi/drm/nova_drm.h    | 36 ++++++++--------------------------
>  3 files changed, 10 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nova/driver.rs b/drivers/gpu/drm/nova/driver.rs
> index 46e13fe795eb..851d50b4dd15 100644
> --- a/drivers/gpu/drm/nova/driver.rs
> +++ b/drivers/gpu/drm/nova/driver.rs
> @@ -95,9 +95,8 @@ impl drm::Driver for NovaDriver {
>      const FEAT_RENDER: bool = true;
>  
>      kernel::declare_drm_ioctls! {
> -        (NOVA_GETPARAM, drm_nova_getparam, ioctl::RENDER_ALLOW, File::get_param),
> +        (NOVA_INFO, drm_nova_info, ioctl::RENDER_ALLOW, File::info),
>          (NOVA_GEM_CREATE, drm_nova_gem_create, ioctl::AUTH | ioctl::RENDER_ALLOW, File::gem_create),
>          (NOVA_GEM_INFO, drm_nova_gem_info, ioctl::AUTH | ioctl::RENDER_ALLOW, File::gem_info),
> -        (NOVA_INFO, drm_nova_info, ioctl::RENDER_ALLOW, File::info),
>      }
>  }
> diff --git a/drivers/gpu/drm/nova/file.rs b/drivers/gpu/drm/nova/file.rs
> index 766a6ddb7e10..a05264917a0b 100644
> --- a/drivers/gpu/drm/nova/file.rs
> +++ b/drivers/gpu/drm/nova/file.rs
> @@ -60,6 +60,7 @@ fn new(reg_data: &DrmRegData<'_>) -> Result<Self> {
>              architecture: spec.chipset.arch().into(),
>              chipid: spec.chipset.into(),
>              vram_size: gsp_static_info.vram_size(),
> +            vram_bar_size: reg_data.api.with(|api| api.bar1_size())?,
>              gpu_gid: gsp_static_info.gpu_gid,
>              ..pin_init::zeroed()
>          };
> @@ -108,23 +109,6 @@ fn open(_dev: &NovaDevice) -> Result<Pin<KBox<Self>>> {
>  }
>  
>  impl File {
> -    /// IOCTL: get_param: Query GPU / driver metadata.
> -    pub(crate) fn get_param(
> -        _dev: &NovaDevice<Registered>,
> -        reg_data: &DrmRegData<'_>,
> -        getparam: &mut uapi::drm_nova_getparam,
> -        _file: &drm::File<File>,
> -    ) -> Result<u32> {
> -        let value = match getparam.param.try_into()? {
> -            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => reg_data.api.with(|api| api.bar1_size())?,
> -            _ => return Err(EINVAL),
> -        };
> -
> -        getparam.value = Into::<u64>::into(value);
> -
> -        Ok(0)
> -    }
> -
>      /// IOCTL: gem_create: Create a new DRM GEM object.
>      pub(crate) fn gem_create(
>          dev: &NovaDevice<Registered>,
> diff --git a/include/uapi/drm/nova_drm.h b/include/uapi/drm/nova_drm.h
> index a74daba6ea94..d7017ed17143 100644
> --- a/include/uapi/drm/nova_drm.h
> +++ b/include/uapi/drm/nova_drm.h
> @@ -18,13 +18,6 @@
>  extern "C" {
>  #endif
>  
> -/*
> - * NOVA_GETPARAM_VRAM_BAR_SIZE
> - *
> - * Query the VRAM BAR size in bytes.
> - */
> -#define NOVA_GETPARAM_VRAM_BAR_SIZE	0x1
> -
>  /**
>   * enum drm_nova_architecture - GPU architecture identifier
>   */
> @@ -77,21 +70,6 @@ enum drm_nova_chipid {
>  	NOVA_DRM_CHIPID_GB207			= 0x1b7,
>  };
>  
> -/**
> - * struct drm_nova_getparam - query GPU and driver metadata
> - */
> -struct drm_nova_getparam {
> -	/**
> -	 * @param: The identifier of the parameter to query.
> -	 */
> -	__u64 param;
> -
> -	/**
> -	 * @value: The value for the specified parameter.
> -	 */
> -	__u64 value;
> -};
> -
>  /**
>   * struct drm_nova_gem_create - create a new DRM GEM object
>   */
> @@ -189,6 +167,11 @@ struct drm_nova_info_gpu {
>  	 */
>  	__u64 vram_size;
>  
> +	/**
> +	 * @vram_bar_size: Size of the PCI BAR aperture used to access VRAM, in bytes.
> +	 */
> +	__u64 vram_bar_size;
> +
>  	/**
>  	 * @gpu_name: NUL-terminated full GPU name.
>  	 */
> @@ -205,21 +188,18 @@ struct drm_nova_info_gpu {
>  	__u8 gpu_gid[16];
>  };
>  
> -#define DRM_NOVA_GETPARAM		0x00
> +#define DRM_NOVA_INFO			0x00
>  #define DRM_NOVA_GEM_CREATE		0x01
>  #define DRM_NOVA_GEM_INFO		0x02
> -#define DRM_NOVA_INFO			0x03
>  
>  /* Note: this is an enum so that it can be resolved by Rust bindgen. */
>  enum {
> -	DRM_IOCTL_NOVA_GETPARAM		= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_GETPARAM,
> -						   struct drm_nova_getparam),
> +	DRM_IOCTL_NOVA_INFO		= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_INFO,
> +						   struct drm_nova_info),
>  	DRM_IOCTL_NOVA_GEM_CREATE	= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_GEM_CREATE,
>  						   struct drm_nova_gem_create),
>  	DRM_IOCTL_NOVA_GEM_INFO		= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_GEM_INFO,
>  						   struct drm_nova_gem_info),
> -	DRM_IOCTL_NOVA_INFO		= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_INFO,
> -						   struct drm_nova_info),
>  };
>  
>  #if defined(__cplusplus)
> 
> base-commit: 10a6623a24a85708650efad7be15182289403cd7
> -- 
> 2.55.0
>