Re: [PATCH 3/4] gpu: nova-core: gsp: Extract usable FB region from GSP

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

On Tue Jun 9, 2026 at 5:04 PM JST, Alexandre Courbot wrote:
> From: Joel Fernandes <joelagnelf@nvidia.com>
>
> Add usable_fb_regions_iter() to GspStaticConfigInfo to extract the first
> usable FB region from GSP's fbRegionInfoParams. Usable regions are those
> that are not reserved or protected.
>
> The extracted region is stored in GetGspStaticInfoReply and exposed as
> usable_fb_region field for use by the memory subsystem.
>
> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  drivers/gpu/nova-core/gsp/commands.rs    |  9 +++++--
>  drivers/gpu/nova-core/gsp/fw/commands.rs | 40 +++++++++++++++++++++++++++++++-
>  2 files changed, 46 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
> index f84de9f4f045..d955f52a93bb 100644
> --- a/drivers/gpu/nova-core/gsp/commands.rs
> +++ b/drivers/gpu/nova-core/gsp/commands.rs
> @@ -5,6 +5,7 @@
>      array,
>      convert::Infallible,
>      ffi::FromBytesUntilNulError,
> +    ops::Range,
>      str::Utf8Error, //
>  };
>  
> @@ -191,15 +192,18 @@ fn init(&self) -> impl Init<Self::Command, Self::InitError> {
>      }
>  }
>  
> -/// The reply from the GSP to the [`GetGspInfo`] command.
> +/// The reply from the GSP to the [`GetGspStaticInfo`] command.
>  pub(crate) struct GetGspStaticInfoReply {
>      gpu_name: [u8; 64],
> +    /// Usable FB (VRAM) region for driver memory allocation.
> +    #[expect(dead_code)]
> +    pub(crate) usable_fb_region: Range<u64>,
>  }
>  
>  impl MessageFromGsp for GetGspStaticInfoReply {
>      const FUNCTION: MsgFunction = MsgFunction::GetGspStaticInfo;
>      type Message = fw::commands::GspStaticConfigInfo;
> -    type InitError = Infallible;
> +    type InitError = Error;
>  
>      fn read(
>          msg: &Self::Message,
> @@ -207,6 +211,7 @@ fn read(
>      ) -> Result<Self, Self::InitError> {
>          Ok(GetGspStaticInfoReply {
>              gpu_name: msg.gpu_name_str(),
> +            usable_fb_region: msg.usable_fb_regions_iter().next().ok_or(ENODEV)?,
>          })
>      }
>  }
> diff --git a/drivers/gpu/nova-core/gsp/fw/commands.rs b/drivers/gpu/nova-core/gsp/fw/commands.rs
> index 7bcc41fc7fa0..d025167927df 100644
> --- a/drivers/gpu/nova-core/gsp/fw/commands.rs
> +++ b/drivers/gpu/nova-core/gsp/fw/commands.rs
> @@ -1,6 +1,8 @@
>  // SPDX-License-Identifier: GPL-2.0
>  // SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
>  
> +use core::ops::Range;
> +
>  use kernel::{
>      device,
>      pci,
> @@ -13,7 +15,8 @@
>  
>  use crate::{
>      gpu::Chipset,
> -    gsp::GSP_PAGE_SIZE, //
> +    gsp::GSP_PAGE_SIZE,
> +    num::IntoSafeCast, //
>  };
>  
>  use super::bindings;
> @@ -129,6 +132,41 @@ impl GspStaticConfigInfo {
>      pub(crate) fn gpu_name_str(&self) -> [u8; 64] {
>          self.0.gpuNameString
>      }
> +
> +    /// Returns an iterator over valid FB regions from GSP firmware data.
> +    fn fb_regions(
> +        &self,
> +    ) -> impl Iterator<Item = &bindings::NV2080_CTRL_CMD_FB_GET_FB_REGION_FB_REGION_INFO> {
> +        let fb_info = &self.0.fbRegionInfoParams;
> +        fb_info
> +            .fbRegion
> +            .iter()
> +            .take(fb_info.numFBRegions.into_safe_cast())
> +            .filter(|reg| reg.limit >= reg.base)

Do you know if we actually get broken values like this (limit < base)?

Also we could print out the `usable_fb_region` as well, if you like?

Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>

> +    }
> +
> +    /// Iterates over usable FB regions from GSP firmware data.
> +    ///
> +    /// Each yielded region is a [`Range<u64>`] suitable for driver memory allocation.
> +    /// Usable regions are those that satisfy all the following properties:
> +    /// - Are not reserved for firmware internal use.
> +    /// - Are not protected (hardware-enforced access restrictions).
> +    /// - Support compression (can use GPU memory compression for bandwidth).
> +    /// - Support ISO (isochronous memory for display requiring guaranteed bandwidth).
> +    pub(crate) fn usable_fb_regions_iter(&self) -> impl Iterator<Item = Range<u64>> + '_ {
> +        self.fb_regions().filter_map(|reg| {
> +            // Filter: not reserved, not protected, supports compression and ISO.
> +            if reg.reserved == 0
> +                && reg.bProtected == 0
> +                && reg.supportCompressed != 0
> +                && reg.supportISO != 0
> +            {
> +                reg.limit.checked_add(1).map(|end| reg.base..end)
> +            } else {
> +                None
> +            }
> +        })
> +    }
>  }
>  
>  // SAFETY: Padding is explicit and will not contain uninitialized data.