[PATCH RFC v6 12/26] nova-core: mm: Add MMU v3 page table types

[Joel Fernandes <joelagnelf@nvidia.com>]

Add page table entry and directory structures for MMU version 3
used by Hopper and later GPUs.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
 drivers/gpu/nova-core/mm/pagetable/mod.rs  |   1 +
 drivers/gpu/nova-core/mm/pagetable/ver3.rs | 286 +++++++++++++++++++++
 2 files changed, 287 insertions(+)
 create mode 100644 drivers/gpu/nova-core/mm/pagetable/ver3.rs

diff --git a/drivers/gpu/nova-core/mm/pagetable/mod.rs b/drivers/gpu/nova-core/mm/pagetable/mod.rs
index 787755e89a5b..3b1324add844 100644
--- a/drivers/gpu/nova-core/mm/pagetable/mod.rs
+++ b/drivers/gpu/nova-core/mm/pagetable/mod.rs
@@ -8,6 +8,7 @@
 
 #![expect(dead_code)]
 pub(crate) mod ver2;
+pub(crate) mod ver3;
 
 use crate::gpu::Architecture;
 
diff --git a/drivers/gpu/nova-core/mm/pagetable/ver3.rs b/drivers/gpu/nova-core/mm/pagetable/ver3.rs
new file mode 100644
index 000000000000..6a5618fbb63d
--- /dev/null
+++ b/drivers/gpu/nova-core/mm/pagetable/ver3.rs
@@ -0,0 +1,286 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! MMU v3 page table types for Hopper and later GPUs.
+//!
+//! This module defines MMU version 3 specific types (Hopper and later GPUs).
+//!
+//! Key differences from MMU v2:
+//! - Unified 40-bit address field for all apertures (v2 had separate sys/vid fields).
+//! - PCF (Page Classification Field) replaces separate privilege/RO/atomic/cache bits.
+//! - KIND field is 4 bits (not 8).
+//! - IS_PTE bit in PDE to support large pages directly.
+//! - No COMPTAGLINE field (compression handled differently in v3).
+//! - No separate ENCRYPTED bit.
+//!
+//! Bit field layouts derived from the NVIDIA OpenRM documentation:
+//! `open-gpu-kernel-modules/src/common/inc/swref/published/hopper/gh100/dev_mmu.h`
+
+#![expect(dead_code)]
+
+use super::{
+    AperturePde,
+    AperturePte, //
+};
+use crate::mm::{
+    Pfn,
+    VramAddress, //
+};
+use kernel::prelude::*;
+
+// Page Classification Field (PCF) - 5 bits for PTEs in MMU v3.
+bitfield! {
+    pub(crate) struct PtePcf(u8), "Page Classification Field for PTEs" {
+        0:0     uncached    as bool, "Bypass L2 cache (0=cached, 1=bypass)";
+        1:1     acd         as bool, "Access counting disabled (0=enabled, 1=disabled)";
+        2:2     read_only   as bool, "Read-only access (0=read-write, 1=read-only)";
+        3:3     no_atomic   as bool, "Atomics disabled (0=enabled, 1=disabled)";
+        4:4     privileged  as bool, "Privileged access only (0=regular, 1=privileged)";
+    }
+}
+
+impl PtePcf {
+    /// Create PCF for read-write mapping (cached, no atomics, regular mode).
+    pub(crate) fn rw() -> Self {
+        Self::default().set_no_atomic(true)
+    }
+
+    /// Create PCF for read-only mapping (cached, no atomics, regular mode).
+    pub(crate) fn ro() -> Self {
+        Self::default().set_read_only(true).set_no_atomic(true)
+    }
+
+    /// Get the raw `u8` value.
+    pub(crate) fn raw_u8(&self) -> u8 {
+        self.0
+    }
+}
+
+impl From<u8> for PtePcf {
+    fn from(val: u8) -> Self {
+        Self(val)
+    }
+}
+
+// Page Classification Field (PCF) - 3 bits for PDEs in MMU v3.
+// Controls Address Translation Services (ATS) and caching.
+bitfield! {
+    pub(crate) struct PdePcf(u8), "Page Classification Field for PDEs" {
+        0:0     uncached    as bool, "Bypass L2 cache (0=cached, 1=bypass)";
+        1:1     no_ats      as bool, "Address Translation Services disabled (0=enabled, 1=disabled)";
+    }
+}
+
+impl PdePcf {
+    /// Create PCF for cached mapping with ATS enabled (default).
+    pub(crate) fn cached() -> Self {
+        Self::default()
+    }
+
+    /// Get the raw `u8` value.
+    pub(crate) fn raw_u8(&self) -> u8 {
+        self.0
+    }
+}
+
+impl From<u8> for PdePcf {
+    fn from(val: u8) -> Self {
+        Self(val)
+    }
+}
+
+// Page Table Entry (PTE) for MMU v3.
+bitfield! {
+    pub(crate) struct Pte(u64), "Page Table Entry for MMU v3" {
+        0:0     valid           as bool, "Entry is valid";
+        2:1     aperture        as u8 => AperturePte, "Memory aperture type";
+        7:3     pcf             as u8 => PtePcf, "Page Classification Field";
+        11:8    kind            as u8, "Surface kind (4 bits, 0x0=pitch, 0xF=invalid)";
+        51:12   frame_number    as u64 => Pfn, "Physical frame number (for all apertures)";
+        63:61   peer_id         as u8, "Peer GPU ID for peer memory (0-7)";
+    }
+}
+
+impl Pte {
+    /// Create a PTE from a `u64` value.
+    pub(crate) fn new(val: u64) -> Self {
+        Self(val)
+    }
+
+    /// Create a valid PTE for video memory.
+    pub(crate) fn new_vram(frame: Pfn, writable: bool) -> Self {
+        let pcf = if writable { PtePcf::rw() } else { PtePcf::ro() };
+        Self::default()
+            .set_valid(true)
+            .set_aperture(AperturePte::VideoMemory)
+            .set_pcf(pcf)
+            .set_frame_number(frame)
+    }
+
+    /// Create an invalid PTE.
+    pub(crate) fn invalid() -> Self {
+        Self::default()
+    }
+
+    /// Get the raw `u64` value.
+    pub(crate) fn raw_u64(&self) -> u64 {
+        self.0
+    }
+}
+
+// Page Directory Entry (PDE) for MMU v3.
+//
+// Note: v3 uses a unified 40-bit address field (v2 had separate sys/vid address fields).
+bitfield! {
+    pub(crate) struct Pde(u64), "Page Directory Entry for MMU v3 (Hopper+)" {
+        0:0     is_pte      as bool, "Entry is a PTE (0=PDE, 1=large page PTE)";
+        2:1     aperture    as u8 => AperturePde, "Memory aperture (0=invalid, 1=vidmem, 2=coherent, 3=non-coherent)";
+        5:3     pcf         as u8 => PdePcf, "Page Classification Field (3 bits for PDE)";
+        51:12   table_frame as u64 => Pfn, "Table frame number (40-bit unified address)";
+    }
+}
+
+impl Pde {
+    /// Create a PDE from a `u64` value.
+    pub(crate) fn new(val: u64) -> Self {
+        Self(val)
+    }
+
+    /// Create a valid PDE pointing to a page table in video memory.
+    pub(crate) fn new_vram(table_pfn: Pfn) -> Self {
+        Self::default()
+            .set_is_pte(false)
+            .set_aperture(AperturePde::VideoMemory)
+            .set_table_frame(table_pfn)
+    }
+
+    /// Create an invalid PDE.
+    pub(crate) fn invalid() -> Self {
+        Self::default().set_aperture(AperturePde::Invalid)
+    }
+
+    /// Check if this PDE is valid.
+    pub(crate) fn is_valid(&self) -> bool {
+        self.aperture() != AperturePde::Invalid
+    }
+
+    /// Get the VRAM address of the page table.
+    pub(crate) fn table_vram_address(&self) -> VramAddress {
+        debug_assert!(
+            self.aperture() == AperturePde::VideoMemory,
+            "table_vram_address called on non-VRAM PDE (aperture: {:?})",
+            self.aperture()
+        );
+        VramAddress::from(self.table_frame())
+    }
+
+    /// Get the raw `u64` value.
+    pub(crate) fn raw_u64(&self) -> u64 {
+        self.0
+    }
+}
+
+// Big Page Table pointer for Dual PDE - 64-bit lower word of the 128-bit Dual PDE.
+bitfield! {
+    pub(crate) struct DualPdeBig(u64), "Big Page Table pointer in Dual PDE (MMU v3)" {
+        0:0     is_pte      as bool, "Entry is a PTE (for large pages)";
+        2:1     aperture    as u8 => AperturePde, "Memory aperture type";
+        5:3     pcf         as u8 => PdePcf, "Page Classification Field";
+        51:8    table_frame as u64, "Table frame (table address 256-byte aligned)";
+    }
+}
+
+impl DualPdeBig {
+    /// Create a big page table pointer from a `u64` value.
+    pub(crate) fn new(val: u64) -> Self {
+        Self(val)
+    }
+
+    /// Create an invalid big page table pointer.
+    pub(crate) fn invalid() -> Self {
+        Self::default().set_aperture(AperturePde::Invalid)
+    }
+
+    /// Create a valid big PDE pointing to a page table in video memory.
+    pub(crate) fn new_vram(table_addr: VramAddress) -> Result<Self> {
+        // Big page table addresses must be 256-byte aligned (shift 8).
+        if table_addr.raw_u64() & 0xFF != 0 {
+            return Err(EINVAL);
+        }
+
+        let table_frame = table_addr.raw_u64() >> 8;
+        Ok(Self::default()
+            .set_is_pte(false)
+            .set_aperture(AperturePde::VideoMemory)
+            .set_table_frame(table_frame))
+    }
+
+    /// Check if this big PDE is valid.
+    pub(crate) fn is_valid(&self) -> bool {
+        self.aperture() != AperturePde::Invalid
+    }
+
+    /// Get the VRAM address of the big page table.
+    pub(crate) fn table_vram_address(&self) -> VramAddress {
+        debug_assert!(
+            self.aperture() == AperturePde::VideoMemory,
+            "table_vram_address called on non-VRAM DualPdeBig (aperture: {:?})",
+            self.aperture()
+        );
+        VramAddress::new(self.table_frame() << 8)
+    }
+
+    /// Get the raw `u64` value.
+    pub(crate) fn raw_u64(&self) -> u64 {
+        self.0
+    }
+}
+
+/// Dual PDE at Level 3 for MMU v3 - 128-bit entry.
+///
+/// Contains both big (64KB) and small (4KB) page table pointers:
+/// - Lower 64 bits: Big Page Table pointer.
+/// - Upper 64 bits: Small Page Table pointer.
+///
+/// ## Note
+///
+/// The big and small page table pointers have different address layouts:
+/// - Big address = field value << 8 (256-byte alignment).
+/// - Small address = field value << 12 (4KB alignment).
+///
+/// This is why `DualPdeBig` is a separate type from `Pde`.
+#[repr(C)]
+#[derive(Debug, Clone, Copy, Default)]
+pub(crate) struct DualPde {
+    /// Big Page Table pointer.
+    pub big: DualPdeBig,
+    /// Small Page Table pointer.
+    pub small: Pde,
+}
+
+impl DualPde {
+    /// Create a dual PDE from raw 128-bit value (two `u64`s).
+    pub(crate) fn new(big: u64, small: u64) -> Self {
+        Self {
+            big: DualPdeBig::new(big),
+            small: Pde::new(small),
+        }
+    }
+
+    /// Create a dual PDE with only the small page table pointer set.
+    pub(crate) fn new_small(table_pfn: Pfn) -> Self {
+        Self {
+            big: DualPdeBig::invalid(),
+            small: Pde::new_vram(table_pfn),
+        }
+    }
+
+    /// Check if the small page table pointer is valid.
+    pub(crate) fn has_small(&self) -> bool {
+        self.small.is_valid()
+    }
+
+    /// Check if the big page table pointer is valid.
+    pub(crate) fn has_big(&self) -> bool {
+        self.big.is_valid()
+    }
+}
-- 
2.34.1