[PATCH v8 17/25] gpu: nova-core: mm: Add Virtual Memory Manager

@@ -7,6 +7,7 @@
 pub(crate) mod pagetable;
 pub(crate) mod pramin;
 pub(crate) mod tlb;
+pub(crate) mod vmm;
 
 use kernel::{
     devres::Devres,

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Virtual Memory Manager for NVIDIA GPU page table management.
+//!
+//! The [`Vmm`] provides high-level page mapping and unmapping operations for GPU
+//! virtual address spaces (Channels, BAR1, BAR2). It wraps the page table walker
+//! and handles TLB flushing after modifications.
+
+#![allow(dead_code)]
+
+use kernel::{
+    gpu::buddy::AllocatedBlocks,
+    prelude::*, //
+};
+
+use crate::mm::{
+    pagetable::{
+        walk::{PtWalk, WalkResult},
+        MmuVersion, //
+    },
+    GpuMm,
+    Pfn,
+    Vfn,
+    VramAddress, //
+};
+
+/// Virtual Memory Manager for a GPU address space.
+///
+/// Each [`Vmm`] instance manages a single address space identified by its Page
+/// Directory Base (`PDB`) address. The [`Vmm`] is used for Channel, BAR1 and
+/// BAR2 mappings.
+pub(crate) struct Vmm {
+    pub(crate) pdb_addr: VramAddress,
+    pub(crate) mmu_version: MmuVersion,
+    /// Page table allocations required for mappings.
+    page_table_allocs: KVec<Pin<KBox<AllocatedBlocks>>>,
+}
+
+impl Vmm {
+    /// Create a new [`Vmm`] for the given Page Directory Base address.
+    pub(crate) fn new(pdb_addr: VramAddress, mmu_version: MmuVersion) -> Result<Self> {
+        // Only MMU v2 is supported for now.
+        if mmu_version != MmuVersion::V2 {
+            return Err(ENOTSUPP);
+        }
+
+        Ok(Self {
+            pdb_addr,
+            mmu_version,
+            page_table_allocs: KVec::new(),
+        })
+    }
+
+    /// Read the [`Pfn`] for a mapped [`Vfn`] if one is mapped.
+    pub(crate) fn read_mapping(&self, mm: &GpuMm, vfn: Vfn) -> Result<Option<Pfn>> {
+        let walker = PtWalk::new(self.pdb_addr, self.mmu_version);
+
+        match walker.walk_to_pte_lookup(mm, vfn)? {
+            WalkResult::Mapped { pfn, .. } => Ok(Some(pfn)),
+            WalkResult::Unmapped { .. } | WalkResult::PageTableMissing => Ok(None),
+        }
+    }
+}