gpu: nova: require little endian

[PATCH v2] gpu: nova: require little endian

Posted by Eliot Courtney 2 months, 1 week ago

The driver already assumes little endian in a lot of locations. For
example, all the code that reads RPCs out of the command queue just
directly interprets the bytes.

Make this explicit in Kconfig.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
The current code assumes little endian in a bunch of places. I think we
should either explicitly decide to be generic on endianness or explicitly
decide not to - having some handling sprinkled around in various
locations seems confusing to me.

I believe that currently e.g. `RUST` transitively depends on
!CPU_BIG_ENDIAN, so this is more about making the decision explicit for
nova-core rather than fixing any kind of hole.
---
Changes in v2:
- Also add to nova-drm (Thanks Danilo)
- Did not take Reviewed-by + Acked-by because commit changed
  substantively
- Link to v1: https://patch.msgid.link/20260406-fix-kconfig-v1-1-8f634499f7f0@nvidia.com
---
 drivers/gpu/drm/nova/Kconfig  | 1 +
 drivers/gpu/nova-core/Kconfig | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/nova/Kconfig b/drivers/gpu/drm/nova/Kconfig
index 3e637ad7b5ba..a2028b8539d7 100644
--- a/drivers/gpu/drm/nova/Kconfig
+++ b/drivers/gpu/drm/nova/Kconfig
@@ -4,6 +4,7 @@ config DRM_NOVA
 	depends on DRM=y
 	depends on PCI
 	depends on RUST
+	depends on !CPU_BIG_ENDIAN
 	select AUXILIARY_BUS
 	select NOVA_CORE
 	default n
diff --git a/drivers/gpu/nova-core/Kconfig b/drivers/gpu/nova-core/Kconfig
index a4f2380654e2..d8456f8eaa05 100644
--- a/drivers/gpu/nova-core/Kconfig
+++ b/drivers/gpu/nova-core/Kconfig
@@ -3,6 +3,7 @@ config NOVA_CORE
 	depends on 64BIT
 	depends on PCI
 	depends on RUST
+	depends on !CPU_BIG_ENDIAN
 	select AUXILIARY_BUS
 	select RUST_FW_LOADER_ABSTRACTIONS
 	default n

---
base-commit: a7a080bb4236ebe577b6776d940d1717912ff6dd
change-id: 20260406-fix-kconfig-3a059f622697

Best regards,
--  
Eliot Courtney <ecourtney@nvidia.com>

Re: [PATCH v2] gpu: nova: require little endian

Posted by Danilo Krummrich 1 month, 2 weeks ago

On Tue, 07 Apr 2026 12:59:50 +0900, Eliot Courtney wrote:
> [PATCH v2] gpu: nova: require little endian

Applied, thanks!

  Branch: drm-rust-next
  Tree:   https://gitlab.freedesktop.org/drm/rust/kernel.git

[1/1] gpu: nova: require little endian
      commit: d39e22cf87b6

The patch will appear in the next linux-next integration (typically within 24
hours on weekdays).

The patch is queued up for the upcoming merge window for the next major kernel
release.

Re: [PATCH v2] gpu: nova: require little endian

Posted by Alexandre Courbot 2 months, 1 week ago

On Tue Apr 7, 2026 at 12:59 PM JST, Eliot Courtney wrote:
> The driver already assumes little endian in a lot of locations. For
> example, all the code that reads RPCs out of the command queue just
> directly interprets the bytes.
>
> Make this explicit in Kconfig.
>
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Letting Danilo pick that one as he mentioned.

Re: [PATCH v2] gpu: nova: require little endian

Posted by Danilo Krummrich 2 months, 1 week ago

On Tue Apr 7, 2026 at 5:59 AM CEST, Eliot Courtney wrote:
> The driver already assumes little endian in a lot of locations. For
> example, all the code that reads RPCs out of the command queue just
> directly interprets the bytes.
>
> Make this explicit in Kconfig.
>
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
> ---
> The current code assumes little endian in a bunch of places. I think we
> should either explicitly decide to be generic on endianness or explicitly
> decide not to - having some handling sprinkled around in various
> locations seems confusing to me.
>
> I believe that currently e.g. `RUST` transitively depends on
> !CPU_BIG_ENDIAN, so this is more about making the decision explicit for
> nova-core rather than fixing any kind of hole.
> ---
> Changes in v2:
> - Also add to nova-drm (Thanks Danilo)
> - Did not take Reviewed-by + Acked-by because commit changed
>   substantively
> - Link to v1: https://patch.msgid.link/20260406-fix-kconfig-v1-1-8f634499f7f0@nvidia.com

Thanks for the new version -- I have one additional question in [1]. Otherwise,
going to pick up once -rc1 is out.

[1] https://lore.kernel.org/all/DHMVA3S2MZWV.1JN7WUBZLRWLV@kernel.org/

Re: [PATCH v2] gpu: nova: require little endian

Posted by Eliot Courtney 2 months, 1 week ago

On Tue Apr 7, 2026 at 11:22 PM JST, Danilo Krummrich wrote:
> On Tue Apr 7, 2026 at 5:59 AM CEST, Eliot Courtney wrote:
>> The driver already assumes little endian in a lot of locations. For
>> example, all the code that reads RPCs out of the command queue just
>> directly interprets the bytes.
>>
>> Make this explicit in Kconfig.
>>
>> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
>> ---
>> The current code assumes little endian in a bunch of places. I think we
>> should either explicitly decide to be generic on endianness or explicitly
>> decide not to - having some handling sprinkled around in various
>> locations seems confusing to me.
>>
>> I believe that currently e.g. `RUST` transitively depends on
>> !CPU_BIG_ENDIAN, so this is more about making the decision explicit for
>> nova-core rather than fixing any kind of hole.
>> ---
>> Changes in v2:
>> - Also add to nova-drm (Thanks Danilo)
>> - Did not take Reviewed-by + Acked-by because commit changed
>>   substantively
>> - Link to v1: https://patch.msgid.link/20260406-fix-kconfig-v1-1-8f634499f7f0@nvidia.com
>
> Thanks for the new version -- I have one additional question in [1]. Otherwise,
> going to pick up once -rc1 is out.
>
> [1] https://lore.kernel.org/all/DHMVA3S2MZWV.1JN7WUBZLRWLV@kernel.org/

Thanks. I think others have answered the question (Thanks Timur and Joel)
so hopefully all good.

Re: [PATCH v2] gpu: nova: require little endian

Posted by Joel Fernandes 2 months, 1 week ago


On 4/6/2026 11:59 PM, Eliot Courtney wrote:
> The driver already assumes little endian in a lot of locations. For
> example, all the code that reads RPCs out of the command queue just
> directly interprets the bytes.
> 
> Make this explicit in Kconfig.
> 
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>

Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>

thanks,

--
Joel Fernandes

Re: [PATCH v2] gpu: nova: require little endian

Posted by Gary Guo 2 months, 1 week ago

On Tue Apr 7, 2026 at 4:59 AM BST, Eliot Courtney wrote:
> The driver already assumes little endian in a lot of locations. For
> example, all the code that reads RPCs out of the command queue just
> directly interprets the bytes.
> 
> Make this explicit in Kconfig.
> 
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
> The current code assumes little endian in a bunch of places. I think we
> should either explicitly decide to be generic on endianness or explicitly
> decide not to - having some handling sprinkled around in various
> locations seems confusing to me.
> 
> I believe that currently e.g. `RUST` transitively depends on
> !CPU_BIG_ENDIAN, so this is more about making the decision explicit for
> nova-core rather than fixing any kind of hole.
> ---
> Changes in v2:
> - Also add to nova-drm (Thanks Danilo)
> - Did not take Reviewed-by + Acked-by because commit changed
>   substantively
> - Link to v1: https://patch.msgid.link/20260406-fix-kconfig-v1-1-8f634499f7f0@nvidia.com
> ---
>  drivers/gpu/drm/nova/Kconfig  | 1 +
>  drivers/gpu/nova-core/Kconfig | 1 +
>  2 files changed, 2 insertions(+)

Re: [PATCH v2] gpu: nova: require little endian

Posted by John Hubbard 2 months, 1 week ago

On 4/6/26 8:59 PM, Eliot Courtney wrote:
> The driver already assumes little endian in a lot of locations. For
> example, all the code that reads RPCs out of the command queue just
> directly interprets the bytes.
> 
> Make this explicit in Kconfig.
> 
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
> ---
> The current code assumes little endian in a bunch of places. I think we
> should either explicitly decide to be generic on endianness or explicitly
> decide not to - having some handling sprinkled around in various
> locations seems confusing to me.
> 
> I believe that currently e.g. `RUST` transitively depends on
> !CPU_BIG_ENDIAN, so this is more about making the decision explicit for
> nova-core rather than fixing any kind of hole.
> ---
> Changes in v2:
> - Also add to nova-drm (Thanks Danilo)
> - Did not take Reviewed-by + Acked-by because commit changed
>    substantively
> - Link to v1: https://patch.msgid.link/20260406-fix-kconfig-v1-1-8f634499f7f0@nvidia.com
> ---
>   drivers/gpu/drm/nova/Kconfig  | 1 +
>   drivers/gpu/nova-core/Kconfig | 1 +
>   2 files changed, 2 insertions(+)

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
-- 
John Hubbard

> 
> diff --git a/drivers/gpu/drm/nova/Kconfig b/drivers/gpu/drm/nova/Kconfig
> index 3e637ad7b5ba..a2028b8539d7 100644
> --- a/drivers/gpu/drm/nova/Kconfig
> +++ b/drivers/gpu/drm/nova/Kconfig
> @@ -4,6 +4,7 @@ config DRM_NOVA
>   	depends on DRM=y
>   	depends on PCI
>   	depends on RUST
> +	depends on !CPU_BIG_ENDIAN
>   	select AUXILIARY_BUS
>   	select NOVA_CORE
>   	default n
> diff --git a/drivers/gpu/nova-core/Kconfig b/drivers/gpu/nova-core/Kconfig
> index a4f2380654e2..d8456f8eaa05 100644
> --- a/drivers/gpu/nova-core/Kconfig
> +++ b/drivers/gpu/nova-core/Kconfig
> @@ -3,6 +3,7 @@ config NOVA_CORE
>   	depends on 64BIT
>   	depends on PCI
>   	depends on RUST
> +	depends on !CPU_BIG_ENDIAN
>   	select AUXILIARY_BUS
>   	select RUST_FW_LOADER_ABSTRACTIONS
>   	default n
> 
> ---
> base-commit: a7a080bb4236ebe577b6776d940d1717912ff6dd
> change-id: 20260406-fix-kconfig-3a059f622697
> 
> Best regards,
> --
> Eliot Courtney <ecourtney@nvidia.com>
>