Re: [PATCH v3 1/5] gpu: nova-core: correct FRTS vidmem offset calculation

On Fri Jul 24, 2026 at 3:56 PM JST, Eliot Courtney wrote:
> Currently, the frts vidmem offset is calculated based on the non-wpr
> heap size and pmu reservation size, but this is not right. The layout
> actually looks like this:
>
> | non-wpr heap | WPR2 .. FRTS | PMU reserved | ... | VGA workspace |
>
> It's just by coincidence + generous alignment that the values happened
> to match. Instead, define a per-architecture reserved size at the end of
> the framebuffer and use this plus the PMU reserved size to calculate the
> frts vidmem offset.
>
> Fixes: d317e4585fa3 ("gpu: nova-core: Hopper/Blackwell: add FSP Chain of =
Trust boot")
> Signed-off-by: Eliot Courtney <[email protected]>
> ---
>  drivers/gpu/nova-core/fb/hal/gb100.rs  |  1 +
>  drivers/gpu/nova-core/fb/hal/gb202.rs  |  1 +
>  drivers/gpu/nova-core/fsp.rs           | 27 +++++++++++++++++++--------
>  drivers/gpu/nova-core/fsp/hal.rs       |  4 ++++
>  drivers/gpu/nova-core/fsp/hal/gb100.rs |  6 ++++++
>  drivers/gpu/nova-core/fsp/hal/gb202.rs |  9 ++++++++-
>  drivers/gpu/nova-core/fsp/hal/gh100.rs |  9 ++++++++-
>  7 files changed, 47 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/fb/hal/gb100.rs b/drivers/gpu/nova-cor=
e/fb/hal/gb100.rs
> index 6e0eba101ca1..51bd0c0bede6 100644
> --- a/drivers/gpu/nova-core/fb/hal/gb100.rs
> +++ b/drivers/gpu/nova-core/fb/hal/gb100.rs
> @@ -78,6 +78,7 @@ fn write_sysmem_flush_page_gb100(bar: Bar0<'_>, addr: B=
ounded<u64, 52>) {
>      );
>  }
> =20
> +// This PMU reservation size is r570-specific.
>  pub(super) const fn pmu_reserved_size_gb100() -> u32 {
>      usize_into_u32::<{ const_align_up(SZ_8M + SZ_16M + SZ_4K, Alignment:=
:new::<SZ_128K>()).unwrap() }>(
>      )
> diff --git a/drivers/gpu/nova-core/fb/hal/gb202.rs b/drivers/gpu/nova-cor=
e/fb/hal/gb202.rs
> index b78e0970f66d..8ec30afcf701 100644
> --- a/drivers/gpu/nova-core/fb/hal/gb202.rs
> +++ b/drivers/gpu/nova-core/fb/hal/gb202.rs
> @@ -71,6 +71,7 @@ fn pmu_reserved_size(&self) -> u32 {
> =20
>      fn non_wpr_heap_size(&self) -> u32 {
>          // Non-WPR heap for GB20x (see Open RM: kgspGetNonWprHeapSize, G=
B202+).
> +        // This size is r570-specific.
>          u32::SZ_2M + u32::SZ_128K
>      }
> =20
> diff --git a/drivers/gpu/nova-core/fsp.rs b/drivers/gpu/nova-core/fsp.rs
> index 1475485bded3..30e53df81aa2 100644
> --- a/drivers/gpu/nova-core/fsp.rs
> +++ b/drivers/gpu/nova-core/fsp.rs
> @@ -134,20 +134,31 @@ struct FspCotMessage {
>  }
> =20
>  impl FspCotMessage {
> +    /// Computes the FRTS vidmem offset for the Chain-of-Trust message. =
It is measured from the end

Let's say "It is measured backwards from the end", so the direction is
clear - I assumed an upwards direction initially, which is intuitively
how you tend to measure things that start at an end offset. :)