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

[Alexandre Courbot]

On Wed Jun 10, 2026 at 12:35 PM JST, Eliot Courtney wrote:
> On Tue Jun 9, 2026 at 5:04 PM JST, Alexandre Courbot wrote:
>> From: Joel Fernandes <joelagnelf@xxxxxxxxxx>
>>
>> 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@xxxxxxxxxx>
>> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
>> ---
>>  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)?

No idea; but filtering for correctness sounds sensible (and is cheap to do).

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

Good idea, this also lets us remove a `dead_code`.