Re: [PATCH v2] gpu: nova-core: firmware: fwsec: use zeroed() to zero-pad buffers

[Alexandre Courbot]

On Wed Oct 7, 2026 at 5:07 PM JST, Thorsten Blum wrote:
> Use KVec::zeroed() to allocate the zero-padded microcode buffer and copy
> the bootloader code into it. Also use KVVec::zeroed() to initialize the
> firmware object's leading zero padding.
>
> Signed-off-by: Thorsten Blum <blum@xxxxxxxxxx>
> ---
> Changes in v2:
> - Add a // PANIC comment to copy_from_slice() (Danilo)
> - v1: https://lore.kernel.org/r/20261006100442.80432-3-blum@xxxxxxxxxx/
> ---
>  drivers/gpu/nova-core/firmware/fwsec/bootloader.rs | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> index ec4d92317a93..1aa08ae8de78 100644
> --- a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> +++ b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
> @@ -137,10 +137,9 @@ pub(crate) fn new(
>                  .align_up(Alignment::new::<{ falcon::MEM_BLOCK_ALIGNMENT }>())
>                  .ok_or(EINVAL)?;
>  
> -            let mut ucode = KVec::with_capacity(aligned_code_size, GFP_KERNEL)?;
> -            ucode.extend_from_slice(code, GFP_KERNEL)?;
> -            ucode.resize(aligned_code_size, 0, GFP_KERNEL)?;
> -
> +            let mut ucode = KVec::zeroed(aligned_code_size, GFP_KERNEL)?;
> +            // PANIC: ucode is sliced to code.len(); code.len() <= aligned_code_size.
> +            ucode[..code.len()].copy_from_slice(code);

As I mentioned on the previous revision, I think not inserting panic
sites should take priority over other considerations. Besides this code
effectively writes he `code` area twice (not that this is a big
concern).

I guess if we want to introduce a new `Vec` API to cover this better, it
should be some kind of constructor cloning a slice - `from_slice` maybe?

>              ucode
>          };
>  
> @@ -162,8 +161,7 @@ pub(crate) fn new(
>                      .ok_or(EOVERFLOW)?
>              };
>  
> -            let mut firmware_obj = KVVec::new();
> -            firmware_obj.extend_with(align_padding, 0u8, GFP_KERNEL)?;
> +            let mut firmware_obj = KVVec::zeroed(align_padding, GFP_KERNEL)?;

This hunk is fine though.