Re: [PATCH v10 03/21] gpu: nova-core: gsp: Expose total physical VRAM end from FB region info

["Eliot Courtney" <ecourtney@nvidia.com>]

On Wed Apr 1, 2026 at 6:20 AM JST, Joel Fernandes wrote:
> Add `total_fb_end()` to `GspStaticConfigInfo` that computes the
> exclusive end address of the highest valid FB region covering both
> usable and GSP-reserved areas.
>
> This allows callers to know the full physical VRAM extent, not just
> the allocatable portion.
>
> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
> ---
>  drivers/gpu/nova-core/gsp/commands.rs    | 6 ++++++
>  drivers/gpu/nova-core/gsp/fw/commands.rs | 7 +++++++
>  2 files changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
> index 41742c1633c8..5e0649024637 100644
> --- a/drivers/gpu/nova-core/gsp/commands.rs
> +++ b/drivers/gpu/nova-core/gsp/commands.rs
> @@ -196,6 +196,9 @@ pub(crate) struct GetGspStaticInfoReply {
>      /// Usable FB (VRAM) region for driver memory allocation.
>      #[expect(dead_code)]
>      pub(crate) usable_fb_region: Range<u64>,
> +    /// End of VRAM.
> +    #[expect(dead_code)]
> +    pub(crate) total_fb_end: u64,
>  }
>  
>  impl MessageFromGsp for GetGspStaticInfoReply {
> @@ -209,9 +212,12 @@ fn read(
>      ) -> Result<Self, Self::InitError> {
>          let (base, size) = msg.first_usable_fb_region().ok_or(ENODEV)?;
>  
> +        let total_fb_end = msg.total_fb_end().ok_or(ENODEV)?;
> +
>          Ok(GetGspStaticInfoReply {
>              gpu_name: msg.gpu_name_str(),
>              usable_fb_region: base..base.saturating_add(size),
> +            total_fb_end,
>          })
>      }
>  }
> diff --git a/drivers/gpu/nova-core/gsp/fw/commands.rs b/drivers/gpu/nova-core/gsp/fw/commands.rs
> index 9fffa74d03f9..46932d5c8c1d 100644
> --- a/drivers/gpu/nova-core/gsp/fw/commands.rs
> +++ b/drivers/gpu/nova-core/gsp/fw/commands.rs
> @@ -163,6 +163,13 @@ pub(crate) fn first_usable_fb_region(&self) -> Option<(u64, u64)> {
>              }
>          })
>      }
> +
> +    /// Compute the end of physical VRAM from all FB regions.
> +    pub(crate) fn total_fb_end(&self) -> Option<u64> {
> +        self.fb_regions()
> +            .map(|reg| reg.limit.saturating_add(1))

I think it would be better to used checked_add here.

> +            .max()
> +    }
>  }
>  
>  // SAFETY: Padding is explicit and will not contain uninitialized data.