John Hubbard
2025-Nov-06 01:27 UTC
[PATCH v5 3/3] 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>
Signed-off-by: John Hubbard <jhubbard at nvidia.com>
---
drivers/gpu/nova-core/gpu.rs | 38 ++++++++++++++++++++++++++++++++++-
drivers/gpu/nova-core/regs.rs | 33 ++++++++++++++++++++++++++++++
2 files changed, 70 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 27b8926977da..8d2bad0e27d1 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -154,6 +154,17 @@ fn try_from(boot0: regs::NV_PMC_BOOT_0) ->
Result<Self> {
}
}
+impl TryFrom<regs::NV_PMC_BOOT_42> for Spec {
+ type Error = Error;
+
+ fn try_from(boot42: regs::NV_PMC_BOOT_42) -> Result<Self> {
+ Ok(Self {
+ chipset: boot42.chipset()?,
+ revision: boot42.revision(),
+ })
+ }
+}
+
impl fmt::Display for Revision {
fn fmt(&self, f: &mut fmt::Formatter<'_>) ->
fmt::Result {
write!(f, "{:x}.{:x}", self.major, self.minor)
@@ -169,9 +180,34 @@ pub(crate) struct Spec {
impl Spec {
fn new(bar: &Bar0) -> Result<Spec> {
+ // Some brief notes about boot0 and boot42, in chronological order:
+ //
+ // NV04 through Volta:
+ //
+ // Not supported by Nova. boot0 is necessary and sufficient to
identify these GPUs.
+ // boot42 may not even exist on some of these GPUs.
+ //
+ // Turing through Blackwell:
+ //
+ // Supported by both Nouveau and Nova. boot0 is still necessary and
sufficient to
+ // identify these GPUs. boot42 exists on these GPUs but we
don't need to use it.
+ //
+ // Rubin:
+ //
+ // Only supported by Nova. Need to use boot42 to fully identify
these GPUs.
+ //
+ // "Future" (after Rubin) GPUs:
+ //
+ // Only supported by Nova. NV_PMC_BOOT's ARCH_0 (bits 28:24)
will be zeroed out, and
+ // ARCH_1 (bit 8:8) will be set to 1, which will mean, "refer
to NV_PMC_BOOT_42".
+
let boot0 = regs::NV_PMC_BOOT_0::read(bar);
- Spec::try_from(boot0)
+ if boot0.use_boot42_instead() {
+ Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
+ } else {
+ Spec::try_from(boot0)
+ }
}
}
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 207b865335af..8b5ff3858210 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -25,6 +25,13 @@
});
impl NV_PMC_BOOT_0 {
+ pub(crate) fn use_boot42_instead(self) -> bool {
+ // "Future" GPUs (some time after Rubin) will set
`architecture_0`
+ // to 0, and `architecture_1` to 1, and put the architecture details in
+ // boot42 instead.
+ self.architecture_0() == 0 && self.architecture_1() == 1
+ }
+
/// Combines `architecture_0` and `architecture_1` to obtain the
architecture of the chip.
pub(crate) fn architecture(self) -> Result<Architecture> {
Architecture::try_from(
@@ -51,6 +58,32 @@ pub(crate) fn revision(self) -> crate::gpu::Revision {
}
}
+register!(NV_PMC_BOOT_42 @ 0x00000108, "Extended architecture
information" {
+ 7:0 implementation as u8, "Implementation version of the
architecture";
+ 15:8 architecture as u8 ?=> Architecture, "Architecture
value";
+ 19:16 minor_revision as u8, "Minor revision of the chip";
+ 23:20 major_revision as u8, "Major revision of the chip";
+});
+
+impl NV_PMC_BOOT_42 {
+ pub(crate) fn chipset(self) -> Result<Chipset> {
+ self.architecture()
+ .map(|arch| {
+ ((arch as u32) << Self::IMPLEMENTATION_RANGE.len())
+ | u32::from(self.implementation())
+ })
+ .and_then(Chipset::try_from)
+ }
+
+ /// Returns the revision information of the chip.
+ pub(crate) fn revision(self) -> crate::gpu::Revision {
+ crate::gpu::Revision {
+ major: self.major_revision(),
+ minor: self.minor_revision(),
+ }
+ }
+}
+
// PBUS
register!(NV_PBUS_SW_SCRATCH @ 0x00001400[64] {});
--
2.51.2
Alexandre Courbot
2025-Nov-06 07:24 UTC
[PATCH v5 3/3] gpu: nova-core: add boot42 support for next-gen GPUs
On Thu Nov 6, 2025 at 10:27 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> > Signed-off-by: John Hubbard <jhubbard at nvidia.com> > --- > drivers/gpu/nova-core/gpu.rs | 38 ++++++++++++++++++++++++++++++++++- > drivers/gpu/nova-core/regs.rs | 33 ++++++++++++++++++++++++++++++ > 2 files changed, 70 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs > index 27b8926977da..8d2bad0e27d1 100644 > --- a/drivers/gpu/nova-core/gpu.rs > +++ b/drivers/gpu/nova-core/gpu.rs > @@ -154,6 +154,17 @@ fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> { > } > } > > +impl TryFrom<regs::NV_PMC_BOOT_42> for Spec { > + type Error = Error; > + > + fn try_from(boot42: regs::NV_PMC_BOOT_42) -> Result<Self> { > + Ok(Self { > + chipset: boot42.chipset()?, > + revision: boot42.revision(), > + }) > + } > +} > + > impl fmt::Display for Revision { > fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { > write!(f, "{:x}.{:x}", self.major, self.minor) > @@ -169,9 +180,34 @@ pub(crate) struct Spec { > > impl Spec { > fn new(bar: &Bar0) -> Result<Spec> { > + // Some brief notes about boot0 and boot42, in chronological order: > + // > + // NV04 through Volta: > + // > + // Not supported by Nova. boot0 is necessary and sufficient to identify these GPUs. > + // boot42 may not even exist on some of these GPUs. > + // > + // Turing through Blackwell: > + // > + // Supported by both Nouveau and Nova. boot0 is still necessary and sufficient to > + // identify these GPUs. boot42 exists on these GPUs but we don't need to use it. > + // > + // Rubin: > + // > + // Only supported by Nova. Need to use boot42 to fully identify these GPUs. > + // > + // "Future" (after Rubin) GPUs: > + // > + // Only supported by Nova. NV_PMC_BOOT's ARCH_0 (bits 28:24) will be zeroed out, and > + // ARCH_1 (bit 8:8) will be set to 1, which will mean, "refer to NV_PMC_BOOT_42".>From the code it looks like Rubin and "Future" GPUs are handled exactlythe same - do we need two paragraphs to describe them, or can we just have one for "Rubing and future GPUs"?> + > let boot0 = regs::NV_PMC_BOOT_0::read(bar); > > - Spec::try_from(boot0) > + if boot0.use_boot42_instead() { > + Spec::try_from(regs::NV_PMC_BOOT_42::read(bar)) > + } else { > + Spec::try_from(boot0) > + } > } > } > > diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs > index 207b865335af..8b5ff3858210 100644 > --- a/drivers/gpu/nova-core/regs.rs > +++ b/drivers/gpu/nova-core/regs.rs > @@ -25,6 +25,13 @@ > }); > > impl NV_PMC_BOOT_0 { > + pub(crate) fn use_boot42_instead(self) -> bool { > + // "Future" GPUs (some time after Rubin) will set `architecture_0` > + // to 0, and `architecture_1` to 1, and put the architecture details in > + // boot42 instead.If this is "some time after Rubin", how do we infer that we must use boot42 for Rubin, as the previous comment suggests?