Add the page table walker implementation that traverses the page table hierarchy for both MMU v2 (5-level) and MMU v3 (6-level) to resolve virtual addresses to physical addresses or find PTE locations.
Currently only v2 has been tested (nova-core currently boots pre-hopper) with some initial preparatory work done for v3. Signed-off-by: Joel Fernandes <[email protected]> --- drivers/gpu/nova-core/mm/pagetable.rs | 1 + drivers/gpu/nova-core/mm/pagetable/walk.rs | 258 +++++++++++++++++++++ 2 files changed, 259 insertions(+) create mode 100644 drivers/gpu/nova-core/mm/pagetable/walk.rs diff --git a/drivers/gpu/nova-core/mm/pagetable.rs b/drivers/gpu/nova-core/mm/pagetable.rs index 38f4f0c6e8ce..5e192679f27c 100644 --- a/drivers/gpu/nova-core/mm/pagetable.rs +++ b/drivers/gpu/nova-core/mm/pagetable.rs @@ -10,6 +10,7 @@ pub(super) mod ver2; pub(super) mod ver3; +pub(super) mod walk; use kernel::prelude::*; diff --git a/drivers/gpu/nova-core/mm/pagetable/walk.rs b/drivers/gpu/nova-core/mm/pagetable/walk.rs new file mode 100644 index 000000000000..a5f6c461f96a --- /dev/null +++ b/drivers/gpu/nova-core/mm/pagetable/walk.rs @@ -0,0 +1,258 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Page table walker implementation for NVIDIA GPUs. +//! +//! This module provides page table walking functionality for MMU v2 and v3. +//! The walker traverses the page table hierarchy to resolve virtual addresses +//! to physical addresses or to find PTE locations. +//! +//! # Page Table Hierarchy +//! +//! ## MMU v2 (Turing/Ampere/Ada) - 5 levels +//! +//! ```text +//! +-------+ +-------+ +-------+ +---------+ +-------+ +//! | PDB |---->| L1 |---->| L2 |---->| L3 Dual |---->| L4 | +//! | (L0) | | | | | | PDE | | (PTE) | +//! +-------+ +-------+ +-------+ +---------+ +-------+ +//! 64-bit 64-bit 64-bit 128-bit 64-bit +//! PDE PDE PDE (big+small) PTE +//! ``` +//! +//! ## MMU v3 (Hopper+) - 6 levels +//! +//! ```text +//! +-------+ +-------+ +-------+ +-------+ +---------+ +-------+ +//! | PDB |---->| L1 |---->| L2 |---->| L3 |---->| L4 Dual |---->| L5 | +//! | (L0) | | | | | | | | PDE | | (PTE) | +//! +-------+ +-------+ +-------+ +-------+ +---------+ +-------+ +//! 64-bit 64-bit 64-bit 64-bit 128-bit 64-bit +//! PDE PDE PDE PDE (big+small) PTE +//! ``` +//! +//! # Result of a page table walk +//! +//! The walker returns a [`WalkResult`] indicating the outcome. + +use core::marker::PhantomData; + +use kernel::{ + device, + prelude::*, // +}; + +use super::{ + DualPdeOps, + MmuConfig, + MmuV2, + MmuV3, + MmuVersion, + PageTableLevel, + PdeOps, + PteOps, // +}; +use crate::{ + mm::{ + pramin, + GpuMm, + Pfn, + Vfn, + VirtualAddress, + VramAddress, // + }, + num::{ + IntoSafeCast, // + }, +}; + +/// Result of walking to a PTE. +#[derive(Debug, Clone, Copy)] +pub(in crate::mm) enum WalkResult { + /// Intermediate page tables are missing (only returned in lookup mode). + PageTableMissing, + /// PTE exists but is invalid (page not mapped). + Unmapped { pte_addr: VramAddress }, + /// PTE exists and is valid (page is mapped). + Mapped { pte_addr: VramAddress, pfn: Pfn }, +} + +/// Result of walking PDE levels only. +/// +/// Returned by [`PtWalkInner::walk_pde_levels()`] to indicate whether all PDE +/// levels resolved or a PDE is missing. +#[derive(Debug, Clone, Copy)] +pub(in crate::mm) enum WalkPdeResult { + /// All PDE levels resolved -- returns PTE page table address. + Complete { + /// VRAM address of the PTE-level page table. + pte_table: VramAddress, + }, + /// A PDE is missing and no prepared page was provided by the closure. + Missing { + /// PDE slot address in the parent page table (where to install). + install_addr: VramAddress, + /// The page table level that is missing. + level: PageTableLevel, + }, +} + +/// Page table walker. +pub(in crate::mm) struct PtWalkInner<M: MmuConfig> { + pdb_addr: VramAddress, + _phantom: PhantomData<M>, +} + +impl<M: MmuConfig> PtWalkInner<M> { + /// Calculate the VRAM address of an entry within a page table. + fn entry_addr(table: VramAddress, level: PageTableLevel, index: u64) -> VramAddress { + let entry_size: u64 = M::entry_size(level).into_safe_cast(); + table + index * entry_size + } + + /// Create a new page table walker. + pub(super) fn new(pdb_addr: VramAddress) -> Self { + Self { + pdb_addr, + _phantom: PhantomData, + } + } + + /// Walk PDE levels with closure-based resolution for missing PDEs. + /// + /// Traverses all PDE levels for the MMU version. At each level, reads the PDE. + /// If valid, extracts the child table address and continues. If missing, calls + /// `resolve_prepared(install_addr)` to resolve the missing PDE. + pub(super) fn walk_pde_levels( + &self, + window: &mut pramin::PraminWindow<'_>, + vfn: Vfn, + resolve_prepared: impl Fn(VramAddress) -> Option<VramAddress>, + ) -> Result<WalkPdeResult> { + let va = VirtualAddress::from(vfn); + let mut cur_table = self.pdb_addr; + + for &level in M::PDE_LEVELS { + let idx = M::level_index(va, level.as_index()); + let install_addr = Self::entry_addr(cur_table, level, idx); + + if level == M::DUAL_PDE_LEVEL { + // 128-bit dual PDE with big+small page table pointers. + let dpde = M::DualPde::read(window, install_addr)?; + if dpde.has_small() { + cur_table = dpde.small_vram_address(); + continue; + } + } else { + // Regular 64-bit PDE. Use `is_valid_vram()` because + // `table_vram_address()` only reads the VRAM frame-number + // bitfield; system-memory PDEs store the address in a + // different (wider) field and would be silently truncated. + let pde = M::Pde::read(window, install_addr)?; + if pde.is_valid_vram() { + cur_table = pde.table_vram_address(); + continue; + } + } + + // PDE missing in HW. Ask caller for resolution. + if let Some(prepared_addr) = resolve_prepared(install_addr) { + cur_table = prepared_addr; + continue; + } + + return Ok(WalkPdeResult::Missing { + install_addr, + level, + }); + } + + Ok(WalkPdeResult::Complete { + pte_table: cur_table, + }) + } + + /// Walk to PTE for lookup only (no allocation). + /// + /// Returns [`WalkResult::PageTableMissing`] if intermediate tables don't exist. + pub(super) fn walk_to_pte_lookup( + &self, + dev: &device::Device<device::Bound>, + mm: &GpuMm, + vfn: Vfn, + ) -> Result<WalkResult> { + let mut window = mm.pramin().get_window(dev)?; + self.walk_to_pte_lookup_with_window(&mut window, vfn) + } + + /// Walk to PTE using a caller-provided PRAMIN window (lookup only). + pub(super) fn walk_to_pte_lookup_with_window( + &self, + window: &mut pramin::PraminWindow<'_>, + vfn: Vfn, + ) -> Result<WalkResult> { + match self.walk_pde_levels(window, vfn, |_| None)? { + WalkPdeResult::Complete { pte_table } => { + Self::read_pte_at_level(window, vfn, pte_table) + } + WalkPdeResult::Missing { .. } => Ok(WalkResult::PageTableMissing), + } + } + + /// Read the PTE at the PTE level given the PTE table address. + fn read_pte_at_level( + window: &mut pramin::PraminWindow<'_>, + vfn: Vfn, + pte_table: VramAddress, + ) -> Result<WalkResult> { + let va = VirtualAddress::from(vfn); + let pte_level = M::PTE_LEVEL; + let pte_idx = M::level_index(va, pte_level.as_index()); + let pte_addr = Self::entry_addr(pte_table, pte_level, pte_idx); + let pte = M::Pte::read(window, pte_addr)?; + + if pte.is_valid() { + return Ok(WalkResult::Mapped { + pte_addr, + pfn: pte.frame_number(), + }); + } + Ok(WalkResult::Unmapped { pte_addr }) + } +} + +macro_rules! pt_walk_dispatch { + ($self:expr, $method:ident ( $($arg:expr),* $(,)? )) => { + match $self { + PtWalk::V2(inner) => inner.$method($($arg),*), + PtWalk::V3(inner) => inner.$method($($arg),*), + } + }; +} + +/// Page table walker dispatch. +pub(in crate::mm) enum PtWalk { + /// MMU v2 (Turing/Ampere/Ada). + V2(PtWalkInner<MmuV2>), + /// MMU v3 (Hopper+). + V3(PtWalkInner<MmuV3>), +} + +impl PtWalk { + /// Create a new page table walker for the given MMU version. + pub(in crate::mm) fn new(pdb_addr: VramAddress, version: MmuVersion) -> Self { + match version { + MmuVersion::V2 => Self::V2(PtWalkInner::<MmuV2>::new(pdb_addr)), + MmuVersion::V3 => Self::V3(PtWalkInner::<MmuV3>::new(pdb_addr)), + } + } + + /// Walk to PTE for lookup. + pub(in crate::mm) fn walk_to_pte( + &self, + dev: &device::Device<device::Bound>, + mm: &GpuMm, + vfn: Vfn, + ) -> Result<WalkResult> { + pt_walk_dispatch!(self, walk_to_pte_lookup(dev, mm, vfn)) + } +} -- 2.34.1
