On Wed Aug 12, 2026 at 1:37 PM CEST, Vladislav Zaharov wrote:
> struct LogBuffers {
> + /// Device the buffers belong to. Also names their debugfs directory.
> + #[cfg(CONFIG_NOVA_CORE_KEEP_GSP_LOGS)]
> + dev: ARef<device::Device>,
> /// Init log buffer.
> loginit: LogBuffer,
> /// Interrupts log buffer.
> @@ -144,6 +167,127 @@ struct LogBuffers {
> logrm: LogBuffer,
> }
>
> +/// Copies of the log buffers of a GPU that is no longer around.
> +#[cfg(CONFIG_NOVA_CORE_KEEP_GSP_LOGS)]
> +struct RetainedLogBuffers {
> + /// Device the buffers came from.
> + dev: ARef<device::Device>,
> + /// Contents of the init log buffer, empty if it was never written to.
> + loginit: KVec<u8>,
> + /// Contents of the interrupts log buffer, empty if it was never written
> to.
> + logintr: KVec<u8>,
> + /// Contents of the RM log buffer, empty if it was never written to.
> + logrm: KVec<u8>,
I think those should use VVec.
> +}
Let's move all the LogBuffer code into gsp/logbuffer.rs to keep gsp.rs clean.
> +#[cfg(CONFIG_NOVA_CORE_KEEP_GSP_LOGS)]
> +impl LogBuffers {
> + /// Preserves whatever the GSP logged, so it can still be read once the
> GPU is gone.
> + ///
> + /// The buffers are DMA allocations of the device and cannot outlive it,
> so their contents are
> + /// copied into memory owned by the module and exposed through fresh
> debugfs entries. Those
> + /// live until the module is unloaded.
> + fn retain(&self) -> Result {
> + let logs = RetainedLogBuffers {
> + dev: self.dev.clone(),
> + loginit: self.loginit.snapshot()?,
> + logintr: self.logintr.snapshot()?,
> + logrm: self.logrm.snapshot()?,
> + };
> +
> + if logs.loginit.is_empty() && logs.logintr.is_empty() &&
> logs.logrm.is_empty() {
> + return Ok(());
> + }
> +
> + let mut retained = crate::RETAINED_LOGS.lock();
> +
> + // An earlier run of the same device may have left a copy behind.
> Its directory carries
> + // the name about to be used again, and its logs are the older ones,
> so drop it first.
> + retained
> + .gpus
> + .retain(|gpu| gpu.dev.name() != self.dev.name());
> +
> + let dir = match retained.dir.clone() {
> + Some(dir) => dir,
> + None => {
> + #[allow(static_mut_refs)]
> + // SAFETY: `DEBUGFS_ROOT` is set before driver registration
> and cleared after
> + // driver unregistration. This runs while a device is still
> bound, or on the way
> + // out of a failed probe, so the driver is registered and
> nothing can be modifying
> + // it.
> + let root: &debugfs::Dir = unsafe {
> crate::DEBUGFS_ROOT.as_ref() }.ok_or(ENODEV)?;
I think we can avoid this additional unsafe if we just create the retained dir
right away in module_init().
> +
> + let dir = root.subdir(c"retained");
> + retained.dir = Some(dir.clone());
> +
> + dir
> + }
> + };
> +
> + let scope = KBox::pin_init(
> + dir.scope(logs, self.dev.name(), |logs, dir| {
> + if !logs.loginit.is_empty() {
> + dir.read_binary_file(c"loginit", &logs.loginit);
> + }
> + if !logs.logintr.is_empty() {
> + dir.read_binary_file(c"logintr", &logs.logintr);
> + }
> + if !logs.logrm.is_empty() {
> + dir.read_binary_file(c"logrm", &logs.logrm);
> + }
> + }),
> + GFP_KERNEL,
> + )?;
> +
> + retained.gpus.push(scope, GFP_KERNEL)?;
> +
> + dev_info!(
dev_dbg!() should be good enough.
> + self.dev,
> + "GSP-RM log buffers retained until the module is unloaded\n"
> + );
> +
> + Ok(())
> + }
