On Fri Mar 20, 2026 at 1:32 PM JST, Alistair Popple wrote: > On 2026-03-18 at 18:14 +1100, Eliot Courtney <[email protected]> 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?
IIRC the largest one I saw in openrm was a few hundred KiB. Theoretically, the largest complete payload you could have in a single message is ~64 KiB since we don't support continuation records on the receive path. > > And is there any concern about performance of vmalloc() vs. kmalloc() for RPC > messages? `KVVec` uses `KVmalloc` which tries `Kmalloc` first. Most of the time, `Kmalloc` should work. So this shouldn't regress performance really in the common case, and it's required for the longer RPCs. > >> Update GspSequence to use KVVec accordingly. >> >> Signed-off-by: Eliot Courtney <[email protected]> >> --- >> 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 >>
