linux-kernel - Re: [PATCH v2 01/10] gpu: nova-core: gsp: warn if data remains after processing a message

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Message-Id: <DFSOBKDE06Y8.13IHB8U8T0AET@garyguo.net>
Date: Mon, 19 Jan 2026 15:33:38 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Alexandre Courbot" <acourbot@...dia.com>, "Danilo Krummrich"
 <dakr@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>, "David Airlie"
 <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>
Cc: "John Hubbard" <jhubbard@...dia.com>, "Alistair Popple"
 <apopple@...dia.com>, "Joel Fernandes" <joelagnelf@...dia.com>, "Timur
 Tabi" <ttabi@...dia.com>, "Edwin Peer" <epeer@...dia.com>, "Eliot Courtney"
 <ecourtney@...dia.com>, <nouveau@...ts.freedesktop.org>,
 <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, "Lyude Paul" <lyude@...hat.com>
Subject: Re: [PATCH v2 01/10] gpu: nova-core: gsp: warn if data remains
 after processing a message

On Tue Dec 16, 2025 at 4:27 AM GMT, Alexandre Courbot wrote:
> Not processing the whole data from a received message is a strong
> indicator of a bug - emit a warning when such cases are detected.
>
> Reviewed-by: Lyude Paul <lyude@...hat.com>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  drivers/gpu/nova-core/gsp/cmdq.rs | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
> index 7985a0b3f769..f0b7ac1ee759 100644
> --- a/drivers/gpu/nova-core/gsp/cmdq.rs
> +++ b/drivers/gpu/nova-core/gsp/cmdq.rs
> @@ -661,7 +661,17 @@ pub(crate) fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Resul
>              let (cmd, contents_1) = M::Message::from_bytes_prefix(message.contents.0).ok_or(EIO)?;
>              let mut sbuffer = SBufferIter::new_reader([contents_1, message.contents.1]);
>  
> -            M::read(cmd, &mut sbuffer).map_err(|e| e.into())
> +            let res = M::read(cmd, &mut sbuffer).map_err(|e| e.into());
> +
> +            if res.is_ok() && !sbuffer.is_empty() {
> +                dev_warn!(
> +                    &self.dev,
> +                    "GSP message {:?} has unprocessed data\n",
> +                    function
> +                );
> +            }

You can also do

    M::read(cmd, &mut sbuffer).map_err(|e| e.info).inspect(|_| {
        if !sbuffer.is_empty() {
            // ...
        }
    })

This does feel like something that would look more elegant with try blocks... I
hope it'll be stable some day.

Best,
Gary

> +
> +            res
>          } else {
>              Err(ERANGE)
>          };