John Hubbard
2025-Nov-15 01:09 UTC
[PATCH v9 3/4] gpu: nova-core: add boot42 support for next-gen GPUs
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 at nvidia.com>
Cc: Danilo Krummrich <dakr at kernel.org>
Cc: Timur Tabi <ttabi at nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf at nvidia.com>
Signed-off-by: John Hubbard <jhubbard at nvidia.com>
---
drivers/gpu/nova-core/gpu.rs | 41 ++++++++++++++++++++++++++++++-----
drivers/gpu/nova-core/regs.rs | 21 +++++++++++++-----
2 files changed, 52 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 88a6d7af9f37..8e04628ca3d9 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -169,6 +169,15 @@ fn from(boot0: regs::NV_PMC_BOOT_0) -> Self {
}
}
+impl From<regs::NV_PMC_BOOT_42> for Revision {
+ fn from(boot0: regs::NV_PMC_BOOT_42) -> Self {
+ Self {
+ major: boot0.major_revision(),
+ minor: boot0.minor_revision(),
+ }
+ }
+}
+
impl fmt::Display for Revision {
fn fmt(&self, f: &mut fmt::Formatter<'_>) ->
fmt::Result {
write!(f, "{:x}.{:x}", self.major, self.minor)
@@ -183,19 +192,41 @@ 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(ENODEV);
+ }
+
+ 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.into(),
+ chipset: boot42.chipset()?,
+ revision: boot42.into(),
})
}
}
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 274e53a1a44d..c6e2e08c754b 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -40,13 +40,24 @@
});
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";
+});
+impl NV_PMC_BOOT_42 {
/// Combines `architecture` and `implementation` to obtain a code unique to
the chipset.
pub(crate) fn chipset(self) -> Result<Chipset> {
self.architecture()
--
2.51.2
Alexandre Courbot
2025-Nov-15 14:13 UTC
[PATCH v9 3/4] gpu: nova-core: add boot42 support for next-gen GPUs
On Sat Nov 15, 2025 at 10:09 AM 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 at nvidia.com> > Cc: Danilo Krummrich <dakr at kernel.org> > Cc: Timur Tabi <ttabi at nvidia.com> > Reviewed-by: Joel Fernandes <joelagnelf at nvidia.com> > Signed-off-by: John Hubbard <jhubbard at nvidia.com> > --- > drivers/gpu/nova-core/gpu.rs | 41 ++++++++++++++++++++++++++++++----- > drivers/gpu/nova-core/regs.rs | 21 +++++++++++++----- > 2 files changed, 52 insertions(+), 10 deletions(-) > > diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs > index 88a6d7af9f37..8e04628ca3d9 100644 > --- a/drivers/gpu/nova-core/gpu.rs > +++ b/drivers/gpu/nova-core/gpu.rs > @@ -169,6 +169,15 @@ fn from(boot0: regs::NV_PMC_BOOT_0) -> Self { > } > } > > +impl From<regs::NV_PMC_BOOT_42> for Revision { > + fn from(boot0: regs::NV_PMC_BOOT_42) -> Self { > + Self { > + major: boot0.major_revision(), > + minor: boot0.minor_revision(), > + } > + } > +}Just one nit: similarly to how we are converting the `TryFrom<BOOT_0> for Spec` into a `TryFrom<BOOT_42>`, I think we don't need to keep `From<BOOT_0> for Revision`. Actually we don't even want it, as using it would mean we are relying on BOOT_0 instead of BOOT_42, which this patchset nicely makes our only source of truth. I'll thus remove the `From<BOOT_0>` implementation before applying.