On Fri Jan 16, 2026 at 10:49 PM CET, Timur Tabi wrote:
> Create read-only debugfs entries for LOGINIT, LOGRM, and LOGINTR, which
> are the three primary printf logging buffers from GSP-RM. LOGPMU will
> be added at a later date, as it requires it support for its RPC message
> first.
>
> This patch uses the `pin_init_scope` feature to create the entries.
> `pin_init_scope` solves the lifetime issue over the `DEBUGFS_ROOT`
> reference by delaying its acquisition until the time the entry is
> actually initialized.
>
> Co-developed-by: Alexandre Courbot <[email protected]>
> Signed-off-by: Alexandre Courbot <[email protected]>
> Signed-off-by: Timur Tabi <[email protected]>
> ---
> drivers/gpu/nova-core/gsp.rs | 45 +++++++++++++++++++++++++++++-------
> 1 file changed, 37 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/gsp.rs b/drivers/gpu/nova-core/gsp.rs
> index 273327c33aa7..4b194bb805b4 100644
> --- a/drivers/gpu/nova-core/gsp.rs
> +++ b/drivers/gpu/nova-core/gsp.rs
> @@ -3,6 +3,7 @@
> mod boot;
>
> use kernel::{
> + c_str,
> debugfs,
> device,
> dma::{
> @@ -101,17 +102,24 @@ fn new(dev: &device::Device<device::Bound>) ->
> Result<Self> {
> }
> }
>
> -/// GSP runtime data.
> -#[pin_data]
> -pub(crate) struct Gsp {
> - /// Libos arguments.
> - pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
> +/// Log buffers used by GSP-RM for debug logging.
> +struct LogBuffers {
> /// Init log buffer.
> loginit: LogBuffer,
> /// Interrupts log buffer.
> logintr: LogBuffer,
> /// RM log buffer.
> logrm: LogBuffer,
> +}
> +
> +/// GSP runtime data.
> +#[pin_data]
> +pub(crate) struct Gsp {
> + /// Libos arguments.
> + pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
> + /// Log buffers, optionally exposed via debugfs.
> + #[pin]
> + logs: debugfs::Scope<LogBuffers>,
> /// Command queue.
> pub(crate) cmdq: Cmdq,
> /// RM arguments.
> @@ -163,15 +171,17 @@ pub(crate) fn new(pdev: &pci::Device<device::Bound>) ->
> impl PinInit<Self, Error
> pin_init::pin_init_scope(move || {
> let dev = pdev.as_ref();
>
> + // Create log buffers before try_pin_init! so they're accessible
> throughout
> + let loginit = LogBuffer::new(dev)?;
> + let logintr = LogBuffer::new(dev)?;
> + let logrm = LogBuffer::new(dev)?;
> +
> Ok(try_pin_init!(Self {
> libos:
> CoherentAllocation::<LibosMemoryRegionInitArgument>::alloc_coherent(
> dev,
> GSP_PAGE_SIZE /
> size_of::<LibosMemoryRegionInitArgument>(),
> GFP_KERNEL | __GFP_ZERO,
> )?,
> - loginit: LogBuffer::new(dev)?,
> - logintr: LogBuffer::new(dev)?,
> - logrm: LogBuffer::new(dev)?,
> cmdq: Cmdq::new(dev)?,
> rmargs:
> CoherentAllocation::<GspArgumentsCached>::alloc_coherent(
> dev,
> @@ -192,6 +202,25 @@ pub(crate) fn new(pdev: &pci::Device<device::Bound>) ->
> impl PinInit<Self, Error
> dma_write!(rmargs[0] =
> fw::GspArgumentsCached::new(cmdq))?;
> dma_write!(libos[3] =
> LibosMemoryRegionInitArgument::new("RMARGS", rmargs))?;
> },
> + logs <- {
> + let log_buffers = LogBuffers {
> + loginit,
> + logintr,
> + logrm,
> + };
> +
> + #[allow(static_mut_refs)]
> + // SAFETY: `DEBUGFS_ROOT` is never modified after
> initialization, so it is
> + // safe to create a shared reference to it.
Well, it is modified in module_exit(), so you have to justify why this can't
race with module_exit(). I.e. because you drop the driver registration first.
You also have to say that the debugfs dir is created before the driver
registration.
> + let debugfs_root = unsafe { crate::DEBUGFS_ROOT.as_ref()
> }
> + .unwrap_or_else(|| debugfs::Dir::empty());
> +
> + debugfs_root.scope(log_buffers, dev.name(), |logs, dir| {
> + dir.read_binary_file(c_str!("loginit"),
> &logs.loginit);
> + dir.read_binary_file(c_str!("logintr"),
> &logs.logintr);
> + dir.read_binary_file(c_str!("logrm"), &logs.logrm);
> + })
> + },
> }))
> })
> }
> --
> 2.52.0
