Re: [PATCH v2 6/9] gpu: nova-core: use KVVec for SBufferIter flush

[Alistair Popple]

On 2026-03-18 at 18:14 +1100, Eliot Courtney <ecourtney@xxxxxxxxxx> wrote...
> Change flush_into_kvec to return KVVec instead of KVec. KVVec uses
> vmalloc for large allocations, which is appropriate since RPC reply
> payloads can be large (>=20 KiB).

Out of curiosity do you know if there is any upper limit on payload size?

And is there any concern about performance of vmalloc() vs. kmalloc() for RPC
messages?

> Update GspSequence to use KVVec accordingly.
> 
> Signed-off-by: Eliot Courtney <ecourtney@xxxxxxxxxx>
> ---
>  drivers/gpu/nova-core/gsp/sequencer.rs | 4 ++--
>  drivers/gpu/nova-core/sbuffer.rs       | 6 +++---
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/gsp/sequencer.rs b/drivers/gpu/nova-core/gsp/sequencer.rs
> index 474e4c8021db..c8f587d2d57b 100644
> --- a/drivers/gpu/nova-core/gsp/sequencer.rs
> +++ b/drivers/gpu/nova-core/gsp/sequencer.rs
> @@ -42,7 +42,7 @@ struct GspSequence {
>      /// Current command index for error reporting.
>      cmd_index: u32,
>      /// Command data buffer containing the sequence of commands.
> -    cmd_data: KVec<u8>,
> +    cmd_data: KVVec<u8>,
>  }
>  
>  impl MessageFromGsp for GspSequence {
> @@ -54,7 +54,7 @@ fn read(
>          msg: &Self::Message,
>          sbuffer: &mut SBufferIter<array::IntoIter<&[u8], 2>>,
>      ) -> Result<Self, Self::InitError> {
> -        let cmd_data = sbuffer.flush_into_kvec(GFP_KERNEL)?;
> +        let cmd_data = sbuffer.read_to_vec(GFP_KERNEL)?;
>          Ok(GspSequence {
>              cmd_index: msg.cmd_index(),
>              cmd_data,
> diff --git a/drivers/gpu/nova-core/sbuffer.rs b/drivers/gpu/nova-core/sbuffer.rs
> index 3a41d224c77a..ae2facdcbdd4 100644
> --- a/drivers/gpu/nova-core/sbuffer.rs
> +++ b/drivers/gpu/nova-core/sbuffer.rs
> @@ -162,11 +162,11 @@ pub(crate) fn read_exact(&mut self, mut dst: &mut [u8]) -> Result {
>          Ok(())
>      }
>  
> -    /// Read all the remaining data into a [`KVec`].
> +    /// Read all the remaining data into a [`KVVec`].
>      ///
>      /// `self` will be empty after this operation.
> -    pub(crate) fn flush_into_kvec(&mut self, flags: kernel::alloc::Flags) -> Result<KVec<u8>> {
> -        let mut buf = KVec::<u8>::new();
> +    pub(crate) fn read_to_vec(&mut self, flags: kernel::alloc::Flags) -> Result<KVVec<u8>> {
> +        let mut buf = KVVec::<u8>::new();
>  
>          if let Some(slice) = core::mem::take(&mut self.cur_slice) {
>              buf.extend_from_slice(slice, flags)?;
> 
> -- 
> 2.53.0
>