[PATCH RFC v6 10/26] nova-core: mm: Add common types for all page table formats

[Joel Fernandes <joelagnelf@nvidia.com>]

Add common page table types shared between MMU v2 and v3. These types
are hardware-agnostic and used by both MMU versions.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
 drivers/gpu/nova-core/mm/mod.rs           |   1 +
 drivers/gpu/nova-core/mm/pagetable/mod.rs | 168 ++++++++++++++++++++++
 2 files changed, 169 insertions(+)
 create mode 100644 drivers/gpu/nova-core/mm/pagetable/mod.rs

diff --git a/drivers/gpu/nova-core/mm/mod.rs b/drivers/gpu/nova-core/mm/mod.rs
index b57016d453ce..6015fc8753bc 100644
--- a/drivers/gpu/nova-core/mm/mod.rs
+++ b/drivers/gpu/nova-core/mm/mod.rs
@@ -4,6 +4,7 @@
 
 #![expect(dead_code)]
 
+pub(crate) mod pagetable;
 pub(crate) mod pramin;
 
 use kernel::sizes::SZ_4K;
diff --git a/drivers/gpu/nova-core/mm/pagetable/mod.rs b/drivers/gpu/nova-core/mm/pagetable/mod.rs
new file mode 100644
index 000000000000..bb3a37cc6ca0
--- /dev/null
+++ b/drivers/gpu/nova-core/mm/pagetable/mod.rs
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Common page table types shared between MMU v2 and v3.
+//!
+//! This module provides foundational types used by both MMU versions:
+//! - Page table level hierarchy
+//! - Memory aperture types for PDEs and PTEs
+
+#![expect(dead_code)]
+
+use crate::gpu::Architecture;
+
+/// MMU version enumeration.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum MmuVersion {
+    /// MMU v2 for Turing/Ampere/Ada.
+    V2,
+    /// MMU v3 for Hopper and later.
+    V3,
+}
+
+impl From<Architecture> for MmuVersion {
+    fn from(arch: Architecture) -> Self {
+        match arch {
+            Architecture::Turing | Architecture::Ampere | Architecture::Ada => Self::V2,
+            // In the future, uncomment:
+            // _ => Self::V3,
+        }
+    }
+}
+
+/// Page Table Level hierarchy for MMU v2/v3.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum PageTableLevel {
+    /// Level 0 - Page Directory Base (root).
+    Pdb,
+    /// Level 1 - Intermediate page directory.
+    L1,
+    /// Level 2 - Intermediate page directory.
+    L2,
+    /// Level 3 - Dual PDE level (Big and Small Page Tables, 128-bit entries).
+    L3,
+    /// Level 4 - Page Table Entries, pointing directly to physical pages.
+    L4,
+}
+
+impl PageTableLevel {
+    /// Get the entry size in bytes for this level.
+    pub(crate) const fn entry_size(&self) -> usize {
+        match self {
+            Self::L3 => 16, // 128-bit dual PDE
+            _ => 8,         // 64-bit PDE/PTE
+        }
+    }
+
+    /// Number of entries per page table (512 for 4KB pages).
+    pub(crate) const ENTRIES_PER_TABLE: usize = 512;
+
+    /// Get the next level in the hierarchy.
+    pub(crate) const fn next(&self) -> Option<PageTableLevel> {
+        match self {
+            Self::Pdb => Some(Self::L1),
+            Self::L1 => Some(Self::L2),
+            Self::L2 => Some(Self::L3),
+            Self::L3 => Some(Self::L4),
+            Self::L4 => None,
+        }
+    }
+
+    /// Check if this is the PTE level.
+    pub(crate) const fn is_pte_level(&self) -> bool {
+        matches!(self, Self::L4)
+    }
+
+    /// Check if this level uses dual PDE (128-bit entries).
+    pub(crate) const fn is_dual_pde_level(&self) -> bool {
+        matches!(self, Self::L3)
+    }
+
+    /// Get all PDE levels (excluding PTE level) for walking.
+    pub(crate) const fn pde_levels() -> [PageTableLevel; 4] {
+        [Self::Pdb, Self::L1, Self::L2, Self::L3]
+    }
+
+    /// Get the level as a numeric index (0-4).
+    pub(crate) const fn as_index(&self) -> u64 {
+        match self {
+            Self::Pdb => 0,
+            Self::L1 => 1,
+            Self::L2 => 2,
+            Self::L3 => 3,
+            Self::L4 => 4,
+        }
+    }
+}
+
+/// Memory aperture for Page Table Entries (`PTE`s).
+///
+/// Determines which memory region the `PTE` points to.
+#[repr(u8)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub(crate) enum AperturePte {
+    /// Local video memory (VRAM).
+    #[default]
+    VideoMemory = 0,
+    /// Peer GPU's video memory.
+    PeerMemory = 1,
+    /// System memory with cache coherence.
+    SystemCoherent = 2,
+    /// System memory without cache coherence.
+    SystemNonCoherent = 3,
+}
+
+// TODO[FPRI]: Replace with `#[derive(FromPrimitive)]` when available.
+impl From<u8> for AperturePte {
+    fn from(val: u8) -> Self {
+        match val {
+            0 => Self::VideoMemory,
+            1 => Self::PeerMemory,
+            2 => Self::SystemCoherent,
+            3 => Self::SystemNonCoherent,
+            _ => Self::VideoMemory,
+        }
+    }
+}
+
+// TODO[FPRI]: Replace with `#[derive(ToPrimitive)]` when available.
+impl From<AperturePte> for u8 {
+    fn from(val: AperturePte) -> Self {
+        val as u8
+    }
+}
+
+/// Memory aperture for Page Directory Entries (`PDE`s).
+///
+/// Note: For `PDE`s, `Invalid` (0) means the entry is not valid.
+#[repr(u8)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub(crate) enum AperturePde {
+    /// Invalid/unused entry.
+    #[default]
+    Invalid = 0,
+    /// Page table is in video memory.
+    VideoMemory = 1,
+    /// Page table is in system memory with coherence.
+    SystemCoherent = 2,
+    /// Page table is in system memory without coherence.
+    SystemNonCoherent = 3,
+}
+
+// TODO[FPRI]: Replace with `#[derive(FromPrimitive)]` when available.
+impl From<u8> for AperturePde {
+    fn from(val: u8) -> Self {
+        match val {
+            1 => Self::VideoMemory,
+            2 => Self::SystemCoherent,
+            3 => Self::SystemNonCoherent,
+            _ => Self::Invalid,
+        }
+    }
+}
+
+// TODO[FPRI]: Replace with `#[derive(ToPrimitive)]` when available.
+impl From<AperturePde> for u8 {
+    fn from(val: AperturePde) -> Self {
+        val as u8
+    }
+}
-- 
2.34.1