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

Eliot Courtney posted 9 patches 2 weeks, 5 days ago
There is a newer version of this series
[PATCH v2 6/9] gpu: nova-core: use KVVec for SBufferIter flush
Posted by Eliot Courtney 2 weeks, 5 days ago 
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).

Update GspSequence to use KVVec accordingly.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 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
Re: [PATCH v2 6/9] gpu: nova-core: use KVVec for SBufferIter flush
Posted by Alistair Popple 2 weeks, 3 days ago 
On 2026-03-18 at 18:14 +1100, Eliot Courtney <ecourtney@nvidia.com> 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@nvidia.com>
> ---
>  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
>
Re: [PATCH v2 6/9] gpu: nova-core: use KVVec for SBufferIter flush
Posted by Eliot Courtney 1 week, 5 days ago 
On Fri Mar 20, 2026 at 1:32 PM JST, Alistair Popple wrote:
> On 2026-03-18 at 18:14 +1100, Eliot Courtney <ecourtney@nvidia.com> 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 <ecourtney@nvidia.com>
>> ---
>>  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
>>

Patchew 2.1-devel-ea86937

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