[PATCH v7 0/4] gpu: nova: add boot42 support for next-gen GPUs

[PATCH v7 0/4] gpu: nova: add boot42 support for next-gen GPUs

[John Hubbard]

Changes in v7:

1) Added a TODO to eventually remove the Default trait from Architecture.
2) Further refined the logic and comments for reading boot0, then boot42.

Changes in v6:

1) Split out a separate patch for implementing Display for Spec.
2) Moved Spec implementation code to its proper location.
3) Significantly changed the use_boot42_instead() logic, and updated the
   comments accordingly.
4) Fixed the boot42 register and field values, which were wrong (and
   had not been exercised before).
5) Imported Revision, to save a few ::'s.
6) Rebased to the very latest drm-rust-next, which now includes the new
   "one 'use' item per line" updates.

Changes in v5:

Two fixes, both from Timur's review feedback (thanks!):

1) Updated both the cover letter, and patch 3 commit description, with
the correct description of the future contents of NV_PMC_BOOT_0.
2) Removed a trailing "boot42" typo from a comment in the code.

Changes in v4:

1) Simplified and improved the decision logic: reads both arch_0 and
arch_1 fields in boot0, and skips the unnecessary is_nv04() logic as
well. Thanks to Timur Tabi and Danilo for noticing these issues.
2) Added a patch to represent Architecture as a u8. This simplifies a
few things. (Thanks to Alex Courbot. I added your Suggested-by to that
patch.)
3) Enhanced the Revision type to do more, which simplifies the callers.
(Thanks to Danilo.)

Changes in v3:

1) Restored the Revision type as recommended by Danilo, but decoupled it
from boot0.
2) Applied Alex Courbot's suggestion to use TryFrom<NV_PMC_BOOT_0/42>
for Spec.
3) Reflowed the new comment documentation to 100 cols, to avoid wasting
a few vertical lines.

Changes in v2:

1) Restored the Spec type, and used that to encapsulate the subsequent
   boot42 enhancements. Thanks to Danilo Krummrich's feedback for that
   improvement.

v1 cover letter (with typos fixed)

NVIDIA GPUs are moving away from using NV_PMC_BOOT_0 to contain
architecture and revision details, and will instead use NV_PMC_BOOT_42
in the future. NV_PMC_BOOT_0 will contain a specific set of values that
will mean "go read NV_PMC_BOOT_42 instead".

Change the selection logic in Nova so that it will claim Turing and
later GPUs. This will work for the foreseeable future, without any
further code changes here, because all NVIDIA GPUs are considered, from
the oldest supported on Linux (NV04), through the future GPUs.

Add some comment documentation to explain, chronologically, how boot0
and boot42 change with the GPU eras, and how that affects the selection
logic.

Also, remove the Revision type, because Revision is no longer valuable
as a stand-alone type, because we only ever want the full information
that Spec provides.

This is based on today's drm-rust-next, which in turn is based on
Linux 6.18-rc2.

John Hubbard (4):
  gpu: nova-core: implement Display for Spec
  gpu: nova-core: prepare Spec and Revision types for boot0/boot42
  gpu: nova-core: make Architecture behave as a u8 type
  gpu: nova-core: add boot42 support for next-gen GPUs

 drivers/gpu/nova-core/gpu.rs  | 82 ++++++++++++++++++++++++++---------
 drivers/gpu/nova-core/regs.rs | 33 +++++++++++---
 2 files changed, 87 insertions(+), 28 deletions(-)


base-commit: e54ad0cd3673c93cdafda58505eaa81610fe3aef
-- 
2.51.2

[PATCH v7 1/4] gpu: nova-core: implement Display for Spec

[John Hubbard]

Implement Display for Spec. This simplifies the dev_info!() code for
printing banners such as:

    NVIDIA (Chipset: GA104, Architecture: Ampere, Revision: a.1)

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 802e71e4f97d..7fd9e91771a6 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -180,6 +180,18 @@ fn new(bar: &Bar0) -> Result<Spec> {
     }
 }
 
+impl fmt::Display for Spec {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "Chipset: {}, Architecture: {:?}, Revision: {}",
+            self.chipset,
+            self.chipset.arch(),
+            self.revision
+        )
+    }
+}
+
 /// Structure holding the resources required to operate the GPU.
 #[pin_data]
 pub(crate) struct Gpu {
@@ -206,13 +218,7 @@ pub(crate) fn new<'a>(
     ) -> impl PinInit<Self, Error> + 'a {
         try_pin_init!(Self {
             spec: Spec::new(bar).inspect(|spec| {
-                dev_info!(
-                    pdev.as_ref(),
-                    "NVIDIA (Chipset: {}, Architecture: {:?}, Revision: {})\n",
-                    spec.chipset,
-                    spec.chipset.arch(),
-                    spec.revision
-                );
+                dev_info!(pdev.as_ref(),"NVIDIA ({})\n", spec);
             })?,
 
             // We must wait for GFW_BOOT completion before doing any significant setup on the GPU.
-- 
2.51.2

[PATCH v7 2/4] gpu: nova-core: prepare Spec and Revision types for boot0/boot42

[John Hubbard]

1) Decouple Revision from boot0.

2) Enhance Revision, which in turn simplifies Spec::new().

3) Also, slightly enhance the comment about Spec, to be more precise.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs  | 25 ++++++++++++-------------
 drivers/gpu/nova-core/regs.rs | 11 ++++++++++-
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 7fd9e91771a6..acf564fee9c8 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -143,17 +143,8 @@ fn try_from(value: u8) -> Result<Self> {
 }
 
 pub(crate) struct Revision {
-    major: u8,
-    minor: u8,
-}
-
-impl Revision {
-    fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
-        Self {
-            major: boot0.major_revision(),
-            minor: boot0.minor_revision(),
-        }
-    }
+    pub(crate) major: u8,
+    pub(crate) minor: u8,
 }
 
 impl fmt::Display for Revision {
@@ -162,7 +153,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
-/// Structure holding the metadata of the GPU.
+/// Structure holding a basic description of the GPU: Architecture, Chipset and Revision.
 pub(crate) struct Spec {
     chipset: Chipset,
     /// The revision of the chipset.
@@ -173,9 +164,17 @@ impl Spec {
     fn new(bar: &Bar0) -> Result<Spec> {
         let boot0 = regs::NV_PMC_BOOT_0::read(bar);
 
+        Spec::try_from(boot0)
+    }
+}
+
+impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
+    type Error = Error;
+
+    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
         Ok(Self {
             chipset: boot0.chipset()?,
-            revision: Revision::from_boot0(boot0),
+            revision: boot0.revision(),
         })
     }
 }
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 934003cab8a8..8c9af3c59708 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -24,7 +24,8 @@
     },
     gpu::{
         Architecture,
-        Chipset, //
+        Chipset,
+        Revision, //
     },
     num::FromSafeCast,
 };
@@ -56,6 +57,14 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
             })
             .and_then(Chipset::try_from)
     }
+
+    /// Returns the revision information of the chip.
+    pub(crate) fn revision(self) -> Revision {
+        Revision {
+            major: self.major_revision(),
+            minor: self.minor_revision(),
+        }
+    }
 }
 
 // PBUS
-- 
2.51.2

[PATCH v7 3/4] gpu: nova-core: make Architecture behave as a u8 type

[John Hubbard]

This allows Architecture to be passed into register!() and bitfield!()
macro calls. That in turn requires a default implementation for
Architecture.

This simplifies transforming BOOT0 (and later, BOOT42) register values
into GPU architectures.

Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index acf564fee9c8..cd58040b681b 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -122,8 +122,14 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 }
 
 /// Enum representation of the GPU generation.
-#[derive(fmt::Debug)]
+///
+/// TODO: remove the `Default` trait implementation, and the `#[default]`
+/// attribute, once the register!() macro (which creates Architecture items) no
+/// longer requires it for read-only fields.
+#[derive(fmt::Debug, Default, Copy, Clone)]
+#[repr(u8)]
 pub(crate) enum Architecture {
+    #[default]
     Turing = 0x16,
     Ampere = 0x17,
     Ada = 0x19,
@@ -142,6 +148,13 @@ fn try_from(value: u8) -> Result<Self> {
     }
 }
 
+impl From<Architecture> for u8 {
+    fn from(value: Architecture) -> Self {
+        // CAST: `Architecture` is `repr(u8)`, so this cast is always lossless.
+        value as u8
+    }
+}
+
 pub(crate) struct Revision {
     pub(crate) major: u8,
     pub(crate) minor: u8,
-- 
2.51.2

[PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[John Hubbard]

NVIDIA GPUs are moving away from using NV_PMC_BOOT_0 to contain
architecture and revision details, and will instead use NV_PMC_BOOT_42
in the future. NV_PMC_BOOT_0 will contain a specific set of values
that will mean "go read NV_PMC_BOOT_42 instead".

Change the selection logic in Nova so that it will claim Turing and
later GPUs. This will work for the foreseeable future, without any
further code changes here, because all NVIDIA GPUs are considered, from
the oldest supported on Linux (NV04), through the future GPUs.

Add some comment documentation to explain, chronologically, how boot0
and boot42 change with the GPU eras, and how that affects the selection
logic.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs  | 32 +++++++++++++++++++++++++++-----
 drivers/gpu/nova-core/regs.rs | 22 ++++++++++++++++------
 2 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index cd58040b681b..8c5f46f6aaac 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -175,19 +175,41 @@ pub(crate) struct Spec {
 
 impl Spec {
     fn new(bar: &Bar0) -> Result<Spec> {
+        // Some brief notes about boot0 and boot42, in chronological order:
+        //
+        // NV04 through NV50:
+        //
+        //    Not supported by Nova. boot0 is necessary and sufficient to identify these GPUs.
+        //    boot42 may not even exist on some of these GPUs.
+        //
+        // Fermi through Volta:
+        //
+        //     Not supported by Nova. boot0 is still sufficient to identify these GPUs, but boot42
+        //     is also guaranteed to be both present and accurate.
+        //
+        // Turing and later:
+        //
+        //     Supported by Nova. Identified by first checking boot0 to ensure that the GPU is not
+        //     from an earlier (pre-Fermi) era, and then using boot42 to precisely identify the GPU.
+        //     Somewhere in the Rubin timeframe, boot0 will no longer have space to add new GPU IDs.
+
         let boot0 = regs::NV_PMC_BOOT_0::read(bar);
 
-        Spec::try_from(boot0)
+        if boot0.is_older_than_fermi() {
+            return Err(ENOTSUPP);
+        }
+
+        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
     }
 }
 
-impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
+impl TryFrom<regs::NV_PMC_BOOT_42> for Spec {
     type Error = Error;
 
-    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
+    fn try_from(boot42: regs::NV_PMC_BOOT_42) -> Result<Self> {
         Ok(Self {
-            chipset: boot0.chipset()?,
-            revision: boot0.revision(),
+            chipset: boot42.chipset()?,
+            revision: boot42.revision(),
         })
     }
 }
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 8c9af3c59708..81097e83c276 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -41,14 +41,24 @@
 });
 
 impl NV_PMC_BOOT_0 {
-    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
-    pub(crate) fn architecture(self) -> Result<Architecture> {
-        Architecture::try_from(
-            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
-        )
+    pub(crate) fn is_older_than_fermi(self) -> bool {
+        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
+        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
+
+        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
+        // GF100, means "older than Fermi".
+        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100
     }
+}
+
+register!(NV_PMC_BOOT_42 @ 0x00000a00, "Extended architecture information" {
+    15:12   minor_revision as u8, "Minor revision of the chip";
+    19:16   major_revision as u8, "Major revision of the chip";
+    23:20   implementation as u8, "Implementation version of the architecture";
+    29:24   architecture as u8 ?=> Architecture, "Architecture value";
+});
 
-    /// Combines `architecture` and `implementation` to obtain a code unique to the chipset.
+impl NV_PMC_BOOT_42 {
     pub(crate) fn chipset(self) -> Result<Chipset> {
         self.architecture()
             .map(|arch| {
-- 
2.51.2

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[Alexandre Courbot]

On Wed Nov 12, 2025 at 1:30 PM JST, John Hubbard wrote:
> NVIDIA GPUs are moving away from using NV_PMC_BOOT_0 to contain
> architecture and revision details, and will instead use NV_PMC_BOOT_42
> in the future. NV_PMC_BOOT_0 will contain a specific set of values
> that will mean "go read NV_PMC_BOOT_42 instead".
>
> Change the selection logic in Nova so that it will claim Turing and
> later GPUs. This will work for the foreseeable future, without any
> further code changes here, because all NVIDIA GPUs are considered, from
> the oldest supported on Linux (NV04), through the future GPUs.
>
> Add some comment documentation to explain, chronologically, how boot0
> and boot42 change with the GPU eras, and how that affects the selection
> logic.
>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Timur Tabi <ttabi@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Love it, it's super simple now. :)

<snip>
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> index 8c9af3c59708..81097e83c276 100644
> --- a/drivers/gpu/nova-core/regs.rs
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -41,14 +41,24 @@
>  });
>  
>  impl NV_PMC_BOOT_0 {
> -    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
> -    pub(crate) fn architecture(self) -> Result<Architecture> {
> -        Architecture::try_from(
> -            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
> -        )
> +    pub(crate) fn is_older_than_fermi(self) -> bool {
> +        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
> +        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
> +
> +        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
> +        // GF100, means "older than Fermi".
> +        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100

We could also keep `architecture` (making it private) and just test for
`self.architecture < NV_PMC_BOOT_0_ARCHITECTURE_GF100`. John, I can do
that when applying the series if you think that makes sense.

Considering that the series has been extensively reviewed during the
previous iterations, I think we can safely apply it for 6.19, so will
proceed once I have an answer.

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[John Hubbard]

On 11/13/25 12:03 AM, Alexandre Courbot wrote:
> On Wed Nov 12, 2025 at 1:30 PM JST, John Hubbard wrote:
...
>>   impl NV_PMC_BOOT_0 {
>> -    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
>> -    pub(crate) fn architecture(self) -> Result<Architecture> {
>> -        Architecture::try_from(
>> -            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
>> -        )
>> +    pub(crate) fn is_older_than_fermi(self) -> bool {
>> +        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
>> +        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
>> +
>> +        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
>> +        // GF100, means "older than Fermi".
>> +        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100
> 
> We could also keep `architecture` (making it private) and just test for
> `self.architecture < NV_PMC_BOOT_0_ARCHITECTURE_GF100`. John, I can do
> that when applying the series if you think that makes sense.

Yes, I think that's a good change to make, sounds good to me.

> 
> Considering that the series has been extensively reviewed during the
> previous iterations, I think we can safely apply it for 6.19, so will
> proceed once I have an answer.

Great!

thanks,
-- 
John Hubbard

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[Joel Fernandes]

Hi John,

On 11/11/2025 11:30 PM, John Hubbard wrote:
> NVIDIA GPUs are moving away from using NV_PMC_BOOT_0 to contain
> architecture and revision details, and will instead use NV_PMC_BOOT_42
> in the future. NV_PMC_BOOT_0 will contain a specific set of values
> that will mean "go read NV_PMC_BOOT_42 instead".
> 
> Change the selection logic in Nova so that it will claim Turing and
> later GPUs. This will work for the foreseeable future, without any
> further code changes here, because all NVIDIA GPUs are considered, from
> the oldest supported on Linux (NV04), through the future GPUs.

[...]

> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index cd58040b681b..8c5f46f6aaac 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -175,19 +175,41 @@ pub(crate) struct Spec {
>  
>  impl Spec {
>      fn new(bar: &Bar0) -> Result<Spec> {
> +        // Some brief notes about boot0 and boot42, in chronological order:
> +        //
> +        // NV04 through NV50:
> +        //
> +        //    Not supported by Nova. boot0 is necessary and sufficient to identify these GPUs.
> +        //    boot42 may not even exist on some of these GPUs.
> +        //
> +        // Fermi through Volta:
> +        //
> +        //     Not supported by Nova. boot0 is still sufficient to identify these GPUs, but boot42
> +        //     is also guaranteed to be both present and accurate.
> +        //
> +        // Turing and later:
> +        //
> +        //     Supported by Nova. Identified by first checking boot0 to ensure that the GPU is not
> +        //     from an earlier (pre-Fermi) era, and then using boot42 to precisely identify the GPU.
> +        //     Somewhere in the Rubin timeframe, boot0 will no longer have space to add new GPU IDs.
> +
>          let boot0 = regs::NV_PMC_BOOT_0::read(bar);
>  
> -        Spec::try_from(boot0)
> +        if boot0.is_older_than_fermi() {
> +            return Err(ENOTSUPP);
> +        }
> +
> +        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))

There is an inconsistency in error return here, if NV04 through NV50, it returns
-ENOTSUPP. For Fermi through Volta, it will read boot42 but will return -ENODEV
because `Spec::try_from()` -> `boot42.chipset()` with return -ENODEV. I am Ok
with either error return, but it would be good to make it consistent.

There also does not seem to be a diagnostic if the chipset is not supported. It
would be good diagnostic that the chipset did not match, right now it will
return -ENODEV, which could mean the device does not exist. -ENOTSUPP is better
though but an actual dmesg error message would be nice.

With these,

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

Thanks.

Re: [PATCH v7 2/4] gpu: nova-core: prepare Spec and Revision types for boot0/boot42

[Joel Fernandes]

On 11/11/2025 11:29 PM, John Hubbard wrote:
> 1) Decouple Revision from boot0.
> 
> 2) Enhance Revision, which in turn simplifies Spec::new().
> 
> 3) Also, slightly enhance the comment about Spec, to be more precise.
> 
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Timur Tabi <ttabi@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  drivers/gpu/nova-core/gpu.rs  | 25 ++++++++++++-------------
>  drivers/gpu/nova-core/regs.rs | 11 ++++++++++-
>  2 files changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index 7fd9e91771a6..acf564fee9c8 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -143,17 +143,8 @@ fn try_from(value: u8) -> Result<Self> {
>  }
>  
>  pub(crate) struct Revision {
> -    major: u8,
> -    minor: u8,
> -}
> -
> -impl Revision {
> -    fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
> -        Self {
> -            major: boot0.major_revision(),
> -            minor: boot0.minor_revision(),
> -        }
> -    }
> +    pub(crate) major: u8,
> +    pub(crate) minor: u8,
>  }
>  
>  impl fmt::Display for Revision {
> @@ -162,7 +153,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>      }
>  }
>  
> -/// Structure holding the metadata of the GPU.
> +/// Structure holding a basic description of the GPU: Architecture, Chipset and Revision.

nit: Can befixed on apply, but the types in the comment need backticks:
`Architecture`, `Chipset` and `Revision`.

thanks,

 - Joel

[...]

Re: [PATCH v7 0/4] gpu: nova: add boot42 support for next-gen GPUs

[Joel Fernandes]

On 11/11/2025 11:29 PM, John Hubbard wrote:
> Changes in v7:
> 
> 1) Added a TODO to eventually remove the Default trait from Architecture.
> 2) Further refined the logic and comments for reading boot0, then boot42.

Other than the few nits I left, looks really good. Thanks!

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

 - Joel

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[John Hubbard]

On 11/13/25 11:59 AM, Joel Fernandes wrote:
> Hi John,
> 
...
>> -        Spec::try_from(boot0)
>> +        if boot0.is_older_than_fermi() {
>> +            return Err(ENOTSUPP);
>> +        }
>> +
>> +        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
> 
> There is an inconsistency in error return here, if NV04 through NV50, it returns
> -ENOTSUPP. For Fermi through Volta, it will read boot42 but will return -ENODEV
> because `Spec::try_from()` -> `boot42.chipset()` with return -ENODEV. I am Ok
> with either error return, but it would be good to make it consistent.
> 

Yes, good catch. It should be -ENOTSUPP for sure.

> There also does not seem to be a diagnostic if the chipset is not supported. It
> would be good diagnostic that the chipset did not match, right now it will
> return -ENODEV, which could mean the device does not exist. -ENOTSUPP is better
> though but an actual dmesg error message would be nice.

Yes. The "not supported" case would happen in two situations:

a) Someone found a pre-Fermi GPU to use for (probably) display, and they
also have a Turing+ GPU in the same system (!), and they have both Nouveau
and Nova drivers available.

Here, it's not really an error situation. If this actually works, then
Nova not supporting the older GPU is just expected operation.

But these older GPUs are not even really directly supported, so this
is a fringe case anyway.

b) A newer GPU is installed, and Nova does not yet support it. Here,
an error message is OK, because Nova is eventually (soon) going to 
support that GPU.

So I think that means an error message is reasonable here.

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

Thanks for the review!

Alex, I think I'd better re-spin and re-test, in order to safely collect
the various small fixes from you and Joel. I can do that today.

thanks,
-- 
John Hubbard

Re: [PATCH v7 2/4] gpu: nova-core: prepare Spec and Revision types for boot0/boot42

[John Hubbard]

On 11/13/25 12:00 PM, Joel Fernandes wrote:
... 
>> -/// Structure holding the metadata of the GPU.
>> +/// Structure holding a basic description of the GPU: Architecture, Chipset and Revision.
> 
> nit: Can befixed on apply, but the types in the comment need backticks:
> `Architecture`, `Chipset` and `Revision`.
> 

Will do.

thanks,
-- 
John Hubbard

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[Alexandre Courbot]

On Fri Nov 14, 2025 at 5:16 AM JST, John Hubbard wrote:
> On 11/13/25 11:59 AM, Joel Fernandes wrote:
>> Hi John,
>> 
> ...
>>> -        Spec::try_from(boot0)
>>> +        if boot0.is_older_than_fermi() {
>>> +            return Err(ENOTSUPP);
>>> +        }
>>> +
>>> +        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
>> 
>> There is an inconsistency in error return here, if NV04 through NV50, it returns
>> -ENOTSUPP. For Fermi through Volta, it will read boot42 but will return -ENODEV
>> because `Spec::try_from()` -> `boot42.chipset()` with return -ENODEV. I am Ok
>> with either error return, but it would be good to make it consistent.
>> 
>
> Yes, good catch. It should be -ENOTSUPP for sure.
>
>> There also does not seem to be a diagnostic if the chipset is not supported. It
>> would be good diagnostic that the chipset did not match, right now it will
>> return -ENODEV, which could mean the device does not exist. -ENOTSUPP is better
>> though but an actual dmesg error message would be nice.
>
> Yes. The "not supported" case would happen in two situations:
>
> a) Someone found a pre-Fermi GPU to use for (probably) display, and they
> also have a Turing+ GPU in the same system (!), and they have both Nouveau
> and Nova drivers available.
>
> Here, it's not really an error situation. If this actually works, then
> Nova not supporting the older GPU is just expected operation.
>
> But these older GPUs are not even really directly supported, so this
> is a fringe case anyway.
>
> b) A newer GPU is installed, and Nova does not yet support it. Here,
> an error message is OK, because Nova is eventually (soon) going to 
> support that GPU.
>
> So I think that means an error message is reasonable here.
>
>> 
>> With these,
>> 
>> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
>> 
>
> Thanks for the review!
>
> Alex, I think I'd better re-spin and re-test, in order to safely collect
> the various small fixes from you and Joel. I can do that today.

Agreed, that will limit the risk of me not capturing everything
properly. Thanks!

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[John Hubbard]

On 11/13/25 12:03 AM, Alexandre Courbot wrote:
> On Wed Nov 12, 2025 at 1:30 PM JST, John Hubbard wrote:
...
>>  impl NV_PMC_BOOT_0 {
>> -    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
>> -    pub(crate) fn architecture(self) -> Result<Architecture> {
>> -        Architecture::try_from(
>> -            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
>> -        )
>> +    pub(crate) fn is_older_than_fermi(self) -> bool {
>> +        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
>> +        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
>> +
>> +        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
>> +        // GF100, means "older than Fermi".
>> +        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100
> 
> We could also keep `architecture` (making it private) and just test for
> `self.architecture < NV_PMC_BOOT_0_ARCHITECTURE_GF100`. John, I can do
> that when applying the series if you think that makes sense.
> 
> Considering that the series has been extensively reviewed during the
> previous iterations, I think we can safely apply it for 6.19, so will
> proceed once I have an answer.

Hi Alex,

It turns out that this doesn't work well, because architecture()
returns an Architecture, not a u8, and then we have to map it back
and the whole things looks a lot worse: complexity on the screen
that serves no purpose.

After looking at several approaches, I've come full circle back to
what this patch has.


thanks,
-- 
John Hubbard

Re: [PATCH v7 4/4] gpu: nova-core: add boot42 support for next-gen GPUs

[Alexandre Courbot]

On Fri Nov 14, 2025 at 10:54 AM JST, John Hubbard wrote:
> On 11/13/25 12:03 AM, Alexandre Courbot wrote:
>> On Wed Nov 12, 2025 at 1:30 PM JST, John Hubbard wrote:
> ...
>>>  impl NV_PMC_BOOT_0 {
>>> -    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
>>> -    pub(crate) fn architecture(self) -> Result<Architecture> {
>>> -        Architecture::try_from(
>>> -            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
>>> -        )
>>> +    pub(crate) fn is_older_than_fermi(self) -> bool {
>>> +        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
>>> +        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
>>> +
>>> +        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
>>> +        // GF100, means "older than Fermi".
>>> +        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100
>> 
>> We could also keep `architecture` (making it private) and just test for
>> `self.architecture < NV_PMC_BOOT_0_ARCHITECTURE_GF100`. John, I can do
>> that when applying the series if you think that makes sense.
>> 
>> Considering that the series has been extensively reviewed during the
>> previous iterations, I think we can safely apply it for 6.19, so will
>> proceed once I have an answer.
>
> Hi Alex,
>
> It turns out that this doesn't work well, because architecture()
> returns an Architecture, not a u8, and then we have to map it back
> and the whole things looks a lot worse: complexity on the screen
> that serves no purpose.
>
> After looking at several approaches, I've come full circle back to
> what this patch has.

Ah right, we would need to add `Fermi` to `Architecture`, which would
now include some architecture we don't support...

In the light of this I agree your original approach makes the most
sense - thanks for checking it out!