Re: [PATCH v12 02/22] gpu: nova-core: gsp: Extract usable FB region from GSP

Joel Fernandes
2026-05-05T18:54:54Z

On 5/2/2026 11:41 AM, Alexandre Courbot wrote:
> On Sun Apr 26, 2026 at 6:14 AM JST, Joel Fernandes wrote:
>> Add first_usable_fb_region() 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.
>>
>> Cc: Nikola Djukic <ndjukic@nvidia.com>
>> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
>> ---
>> drivers/gpu/nova-core/gsp/commands.rs | 11 ++++--
>> drivers/gpu/nova-core/gsp/fw/commands.rs | 45 +++++++++++++++++++++++-
>> 2 files changed, 52 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
>> index c89c7b57a751..d18abd8b5f04 100644
>> --- a/drivers/gpu/nova-core/gsp/commands.rs
>> +++ b/drivers/gpu/nova-core/gsp/commands.rs
>> @@ -4,6 +4,7 @@
>> array,
>> convert::Infallible,
>> ffi::FromBytesUntilNulError,
>> + ops::Range,
>> str::Utf8Error, //
>> };
>>
>> @@ -189,15 +190,18 @@ 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 = GspStaticConfigInfo;
>> - type InitError = Infallible;
>> + type InitError = Error;
>>
>> fn read(
>> msg: &Self::Message,
>> @@ -205,6 +209,7 @@ fn read(
>> ) -> Result<Self, Self::InitError> {
>> Ok(GetGspStaticInfoReply {
>> gpu_name: msg.gpu_name_str(),
>> + usable_fb_region: msg.first_usable_fb_region().ok_or(ENODEV)?,
>> })
>> }
>> }
>> @@ -233,7 +238,7 @@ pub(crate) fn gpu_name(&self) -> core::result::Result<&str, GpuNameError> {
>> }
>> }
>>
>> -/// Send the [`GetGspInfo`] command and awaits for its reply.
>> +/// Send the [`GetGspStaticInfo`] command and awaits for its reply.
>> pub(crate) fn get_gsp_info(cmdq: &Cmdq, bar: &Bar0) -> Result<GetGspStaticInfoReply> {
>> cmdq.send_command(bar, GetGspStaticInfo)
>> }
>> diff --git a/drivers/gpu/nova-core/gsp/fw/commands.rs b/drivers/gpu/nova-core/gsp/fw/commands.rs
>> index db46276430be..a34d29280430 100644
>> --- a/drivers/gpu/nova-core/gsp/fw/commands.rs
>> +++ b/drivers/gpu/nova-core/gsp/fw/commands.rs
>> @@ -1,5 +1,7 @@
>> // SPDX-License-Identifier: GPL-2.0
>>
>> +use core::ops::Range;
>> +
>> use kernel::{
>> device,
>> pci,
>> @@ -10,7 +12,10 @@
>> }, //
>> };
>>
>> -use crate::gsp::GSP_PAGE_SIZE;
>> +use crate::{
>> + gsp::GSP_PAGE_SIZE,
>> + num::IntoSafeCast, //
>> +};
>>
>> use super::bindings;
>>
>> @@ -121,6 +126,44 @@ 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)
>> + }
>> +
>> + /// Extracts the first usable FB region from GSP firmware data.
>> + ///
>> + /// Returns the first region suitable for driver memory allocation as a [`Range<u64>`].
>> + /// 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).
>
> "can use GPU memory compression for saving bandwidth" maybe?

Done.

>
>> + /// - Support ISO (isochronous memory for display requiring guaranteed bandwidth).
>> + ///
>> + /// TODO: Multiple discontinuous usable regions of RAM are possible in
>> + /// special cases. We need to support it.
>> + pub(crate) fn first_usable_fb_region(&self) -> Option<Range<u64>> {
>
> Let's be forward-thinking, and turn this method into
> `usable_fb_regions_iter`, returning an iterator. It is trivial to do
> (just turn `find_map` into `filter`), we will need it later, and for now
> the caller can just do `next()` to get the first region.

Done. Indeed, it does not add more LOC while supporting multiple regions.

thanks,
--
Joel Fernandes