feat(RV64): implement dynamic memory/cpu decider, timer and interrupt controller #659

PeterWrighten · 2025-11-11T10:16:28Z

Description

In order to close #463 , #489, #487 .

Register and implement Interrupt Controller and Timer.

FDT Based Dynamic Decider is implemented as the following design.

Created FDT(Flattened Device Tree) parser for dynamic memory detection from device tree, with
fallback mechanisms. (Using fdt crate)
Dynamic Heap Size and Start Decider implementation in vm.rs
Dynamic CPU Counts implementation.

How was this PR tested?

I tested this heap decider with QEMU memory size 512M, 1G, and 2G. Test results are shown as the following.
Both heap and VM are initialized successfully by using Dynamic Heap Decider.

// 512M Memory Size

qemu-system-riscv64 -machine virt -bios none -kernel target/riscv64gc-unknown-none-elf/release/awkernel -m 512M -nographic -smp 4 -monitor telnet::5556,server,nowait

=== AWkernel RV64 Starting ===
Console port initialized
UART driver initialized
Setting up heap allocation...
Memory detected from boot DTB pointer at 0x00009fe09fe00000
Detected RAM size: 0x0000000020000000
Using dynamic heap configuration\r\nHeap allocation complete\r\nInitializing page allocator...
Initializing kernel space...
Memory detected from boot DTB pointer at 0x00009fe09fe00000
Detected RAM size: 0x0000000020000000
Mapping kernel text section...
Mapping kernel rodata section...
Mapping kernel data section...
Mapping kernel bss section...
Mapping physical memory...
  from ekernel: 0x800d7000
  to MEMORY_END: 0xa0000000 (dynamic)
Memory detected from boot DTB pointer at 0x00009fe09fe00000
Detected RAM size: 0x0000000020000000
Dynamic heap calculation:
  Kernel end: 0x800d7000
  Heap start: 0x800d7000
  Memory end: 0xa0000000
  Max heap size: 0x1ff29000
Activating kernel space...
Virtual memory system initialized
Initializing RISC-V interrupt controller...\r\nInitializing RISC-V timer...\r\nTimer and interrupt controller initialized\r\n[            3 INFO] AWkernel RV64 primary CPU initialization complete
[            5 INFO] CPU#0 is starting.
[            6 INFO] CPU#2 is starting.
[            6 INFO] CPU#3 is starting.
[            7 INFO] CPU#1 is starting.
[            8 INFO] interrupt::INTERRUPT_CONTROLLER has been initialized.
[            9 INFO] interrupt::PREEMPT_FN has been initialized.
[           10 INFO] timer::TIMER has been initialized.
[           12 INFO] A local timer has been initialized.

// 1G Memory Size

qemu-system-riscv64 -machine virt -bios none -kernel target/riscv64gc-unknown-none-elf/release/awkernel -m 1G -nographic -smp 4 -monitor telnet::5556,server,nowait

=== AWkernel RV64 Starting ===
Console port initialized
UART driver initialized
Setting up heap allocation...
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000040000000
Using dynamic heap configuration\r\nHeap allocation complete\r\nInitializing page allocator...
Initializing kernel space...
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000040000000
Mapping kernel text section...
Mapping kernel rodata section...
Mapping kernel data section...
Mapping kernel bss section...
Mapping physical memory...
  from ekernel: 0x800d7000
  to MEMORY_END: 0xc0000000 (dynamic)
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000040000000
Dynamic heap calculation:
  Kernel end: 0x800d7000
  Heap start: 0x800d7000
  Memory end: 0xc0000000
  Max heap size: 0x3ff29000
Activating kernel space...
Virtual memory system initialized
Initializing RISC-V interrupt controller...\r\nInitializing RISC-V timer...\r\nTimer and interrupt controller initialized\r\n[            3 INFO] AWkernel RV64 primary CPU initialization complete
[            5 INFO] CPU#0 is starting.
[            6 INFO] CPU#3 is starting.
[            6 INFO] CPU#1 is starting.
[            7 INFO] CPU#2 is starting.
[            7 INFO] interrupt::INTERRUPT_CONTROLLER has been initialized.
[            8 INFO] interrupt::PREEMPT_FN has been initialized.
[            9 INFO] timer::TIMER has been initialized.
[           11 INFO] A local timer has been initialized.

// 2G Memory Size

qemu-system-riscv64 -machine virt -bios none -kernel target/riscv64gc-unknown-none-elf/release/awkernel -m 2G -nographic -smp 4 -monitor telnet::5556,server,nowait

=== AWkernel RV64 Starting ===
Console port initialized
UART driver initialized
Setting up heap allocation...
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000080000000
Using dynamic heap configuration\r\nHeap allocation complete\r\nInitializing page allocator...
Initializing kernel space...
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000080000000
Mapping kernel text section...
Mapping kernel rodata section...
Mapping kernel data section...
Mapping kernel bss section...
Mapping physical memory...
  from ekernel: 0x800d7000
  to MEMORY_END: 0x00000000 (dynamic)
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000080000000
Dynamic heap calculation:
  Kernel end: 0x800d7000
  Heap start: 0x800d7000
  Memory end: 0x00000000
  Max heap size: 0x7ff29000
Activating kernel space...
Virtual memory system initialized
Initializing RISC-V interrupt controller...\r\nInitializing RISC-V timer...\r\nTimer and interrupt controller initialized\r\n[            3 INFO] AWkernel RV64 primary CPU initialization complete
[            6 INFO] CPU#0 is starting.
[            6 INFO] CPU#3 is starting.
[            7 INFO] CPU#2 is starting.
[            8 INFO] CPU#1 is starting.
[            8 INFO] interrupt::INTERRUPT_CONTROLLER has been initialized.
[            9 INFO] interrupt::PREEMPT_FN has been initialized.
[           10 INFO] timer::TIMER has been initialized.
[           12 INFO] A local timer has been initialized.

After Implementation of Interrupt Controller and timer, the RV64 version kernel worked well as the following.

// All basic function including timer, interrupt controller and dynamic cpu counts worked well
make qemu-riscv64
qemu-system-riscv64 -machine virt -bios none -kernel target/riscv64gc-unknown-none-elf/release/awkernel -m 1G -nographic -smp 4 -monitor telnet::5556,server,nowait

=== AWkernel RV64 Starting ===
Console port initialized
UART driver initialized
Setting up heap allocation...
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000040000000
Using dynamic heap configuration
Heap allocation complete
Initializing page allocator...
Initializing kernel space...
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000040000000
Mapping kernel text section...
Mapping kernel rodata section...
Mapping kernel data section...
Mapping kernel bss section...
Mapping physical memory...
  from ekernel: 0x00000000800df000
  to MEMORY_END: 0x00000000c0000000 (dynamic)
Memory detected from boot DTB pointer at 0x0000bfe0bfe00000
Detected RAM size: 0x0000000040000000
Dynamic heap calculation:
  Kernel end: 0x00000000800df000
  Heap start: 0x00000000800df000
  Memory end: 0x00000000c0000000
  Max heap size: 0x000000003ff21000
Activating kernel space...
Virtual memory system initialized
Initializing RISC-V interrupt controller...
Initializing RISC-V timer...
Timer and interrupt controller initialized
[            1 INFO] AWkernel RV64 primary CPU initialization complete
Detected 00000004 CPUs from boot DTB
[            5 INFO] CPU#0 is starting.
[            6 INFO] CPU#1 is starting.
[            6 INFO] CPU#2 is starting.
[            7 INFO] CPU#3 is starting.
[            7 INFO] interrupt::INTERRUPT_CONTROLLER has been initialized.
[            8 INFO] interrupt::PREEMPT_FN has been initialized.
[            9 INFO] timer::TIMER has been initialized.
[           12 INFO] A local timer has been initialized.
[           15 INFO] Starting [Awkernel] network service.

PeterWrighten

[WIP] Some Debugging code Modification required

kernel/src/arch/rv64/kernel_main.rs

Copilot

Pull Request Overview

This PR implements dynamic memory/CPU detection, timer, and interrupt controller support for the RV64 architecture to close issues #463, #489, and #487. The implementation uses Flattened Device Tree (FDT) parsing to dynamically detect system resources instead of relying on hardcoded values.

Key Changes:

Added FDT-based dynamic memory and CPU count detection with fallback mechanisms
Implemented RISC-V PLIC (Platform-Level Interrupt Controller) and timer support
Restructured boot sequence to initialize heap before memory management (required for page tables)

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
`kernel/src/arch/rv64/timer.rs`	New RISC-V timer implementation using ACLINT MTIME/MTIMECMP registers
`kernel/src/arch/rv64/interrupt_controller.rs`	New PLIC interrupt controller implementation with IPI support
`kernel/src/arch/rv64/kernel_main.rs`	Restructured initialization sequence with dynamic heap allocation and DTB registration
`kernel/src/arch/rv64/boot.S`	Added M-mode trap handlers for timer and software interrupts, DTB pointer preservation
`kernel/src/arch/rv64/config.rs`	Removed hardcoded `HEAP_START` constant
`awkernel_lib/src/arch/rv64/fdt.rs`	New FDT parser for memory and CPU detection with fallback mechanisms
`awkernel_lib/src/arch/rv64/vm.rs`	Dynamic heap size calculation based on detected memory
`awkernel_lib/src/arch/rv64.rs`	Added memory/CPU detection functions and DTB pointer management
`awkernel_lib/src/arch/rv64/delay.rs`	Fixed uptime calculation to use relative time from boot
`awkernel_lib/src/interrupt.rs`	Added RISC-V specific IRQ handler
`kernel/ld/rv64-link.lds`	Changed entry point from 0x80200000 to 0x80000000 for `-bios none`
`awkernel_lib/Cargo.toml`	Added `fdt` crate dependency for rv64 feature

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

kernel/src/arch/rv64/timer.rs

kernel/src/arch/rv64/interrupt_controller.rs

awkernel_lib/src/arch/rv64/fdt.rs

awkernel_lib/src/arch/rv64/delay.rs

- Created FDT parser for dynamic memory/cpu detection from device tree, with fallback mechanisms - Register and implement RISC-V timer - Register and implement interrupt controller and IPI

awkernel_lib/src/arch/rv64.rs

awkernel_lib/src/arch/rv64/fdt.rs

awkernel_lib/src/arch/rv64/vm.rs

…plicit implementation

# Conflicts: # awkernel_lib/src/arch/rv64/vm.rs

ytakano · 2025-11-20T08:02:16Z

awkernel_lib/src/arch/rv64/vm.rs

+
+    // Calculate available memory after kernel
+    let kernel_end = PhyAddr::from_usize(ekernel as *const () as usize);
+    let memory_end = PhyAddr::from_usize(memory_end_addr as usize);


ekernel to MEMORY_END will be used by MMU for the page table as follows.

awkernel/awkernel_lib/src/arch/rv64/frame_allocator.rs

Lines 45 to 49 in e9ef59c

if let Some(allocator_ref) = allocator.as_mut() {

allocator_ref.init(

PhyAddr::from_usize(ekernel as *const () as usize).ceil(),

PhyAddr::from_usize(MEMORY_END as usize).floor(),

);

ekernel to memory_end_addr will be used by heap.

I think some memory frames are used as heap memory and page tables.
As a result of this, the page table will be corrupted.

ytakano · 2025-11-20T08:18:54Z

Following pseudo code explain how to construct heap memory region dynamically.

fn map_heap_region() {
    let mut frame_allocator = FrameAllocator.new(detected_phy_start, detected_phy_end);

    let heap_virt_addr_start = SomeValue;
    let i = 0;

    while let Some(frame) in frame_allocator.alloc() {
        page_table.map_to(heap_virt_addr_start + i * PAGE_SIZE, frame.phy_addr, &mut frame_allocator);
        i += 1;
    }

    let detect_heap_end = heap_virt_addr_start + i * PAGE_SIZE;
}

impl PageTable {
    fn map_to(virt_addr: VirtAddr, phy_addr: PhysAddr, frame_allocator: &mut FrameAllocator) {
         // map `virt_addr` to `phy_addr`
         // if necessary, use `frame_allocator.alloc()` to allocate a page for the page table.
    }
}

PeterWrighten · 2025-11-20T13:35:47Z

Following pseudo code explain how to construct heap memory region dynamically.

fn map_heap_region() {
    let mut frame_allocator = FrameAllocator.new(detected_phy_start, detected_phy_end);

    let heap_virt_addr_start = SomeValue;
    let i = 0;

    while let Some(frame) in frame_allocator.alloc() {
        page_table.map_to(heap_virt_addr_start + i * PAGE_SIZE, frame.phy_addr, &mut frame_allocator);
        i += 1;
    }

    let detect_heap_end = heap_virt_addr_start + i * PAGE_SIZE;
}

impl PageTable {
    fn map_to(virt_addr: VirtAddr, phy_addr: PhysAddr, frame_allocator: &mut FrameAllocator) {
         // map `virt_addr` to `phy_addr`
         // if necessary, use `frame_allocator.alloc()` to allocate a page for the page table.
    }
}

I consider the following logics would make frame allocator exhausted, but seems a balanced solution.

while let Some(frame) in frame_allocator.alloc() {
         page_table.map_to(heap_virt_addr_start + i * PAGE_SIZE, frame.phy_addr, &mut frame_allocator);
         i += 1;
}

ytakano · 2025-11-21T07:56:09Z

I consider the following logics would make frame allocator exhausted, but seems a balanced solution.

while let Some(frame) in frame_allocator.alloc() {
         page_table.map_to(heap_virt_addr_start + i * PAGE_SIZE, frame.phy_addr, &mut frame_allocator);
         i += 1;
}

Yes.
By using this algorithm, all memory frame will be used by either the heap memory or the page table.

PeterWrighten force-pushed the fix-rv64-heap-pagetable branch 3 times, most recently from dc941ae to ae727a2 Compare November 11, 2025 11:22

PeterWrighten marked this pull request as draft November 11, 2025 11:25

PeterWrighten force-pushed the fix-rv64-heap-pagetable branch from ae727a2 to d665eac Compare November 11, 2025 11:38

PeterWrighten commented Nov 11, 2025

View reviewed changes

kernel/src/arch/rv64/kernel_main.rs Outdated Show resolved Hide resolved

PeterWrighten marked this pull request as ready for review November 11, 2025 11:46

PeterWrighten requested a review from ytakano November 11, 2025 11:46

PeterWrighten changed the title ~~fix/feat(RV64): implement dynamic heap start/size decider by using fdt crate and reading DTB pointer when booting~~ fix/feat(RV64): implement dynamic heap start/size decider by using fdt crate and reading DTB pointer when booting, and timer Nov 12, 2025

PeterWrighten force-pushed the fix-rv64-heap-pagetable branch from d665eac to ef55de7 Compare November 12, 2025 10:59

PeterWrighten changed the title ~~fix/feat(RV64): implement dynamic heap start/size and cpu counts decider by using fdt crate and reading DTB pointer when booting, Interrupt Controller and timer~~ feat(RV64): implement dynamic memory/cpu decider, timer and interrupt controller Nov 12, 2025

PeterWrighten self-assigned this Nov 12, 2025

ytakano requested a review from Copilot November 14, 2025 07:32

Copilot AI reviewed Nov 14, 2025

View reviewed changes

feat(RV64): implement dynamic memory/cpu decider, timer and interrupt

67fb94e

- Created FDT parser for dynamic memory/cpu detection from device tree, with fallback mechanisms - Register and implement RISC-V timer - Register and implement interrupt controller and IPI

PeterWrighten force-pushed the fix-rv64-heap-pagetable branch from ef55de7 to 67fb94e Compare November 14, 2025 12:42

ytakano reviewed Nov 19, 2025

View reviewed changes

awkernel_lib/src/arch/rv64.rs Outdated Show resolved Hide resolved

awkernel_lib/src/arch/rv64.rs Show resolved Hide resolved

awkernel_lib/src/arch/rv64.rs Outdated Show resolved Hide resolved

awkernel_lib/src/arch/rv64.rs Outdated Show resolved Hide resolved

ytakano reviewed Nov 19, 2025

View reviewed changes

awkernel_lib/src/arch/rv64/fdt.rs Outdated Show resolved Hide resolved

ytakano reviewed Nov 19, 2025

View reviewed changes

awkernel_lib/src/arch/rv64/vm.rs Outdated Show resolved Hide resolved

awkernel_lib/src/arch/rv64/vm.rs Outdated Show resolved Hide resolved

refactor(RV64): refactor Dynamic Decider's memory end detector for ex…

b52a912

…plicit implementation

PeterWrighten force-pushed the fix-rv64-heap-pagetable branch from 0667506 to b52a912 Compare November 19, 2025 11:14

Merge remote-tracking branch 'origin/main' into fix-rv64-heap-pagetable

1b3a54d

# Conflicts: # awkernel_lib/src/arch/rv64/vm.rs

PeterWrighten force-pushed the fix-rv64-heap-pagetable branch from 158f627 to 1b3a54d Compare November 19, 2025 11:23

PeterWrighten requested a review from ytakano November 19, 2025 11:29

ytakano reviewed Nov 20, 2025

View reviewed changes

Merge branch 'main' into fix-rv64-heap-pagetable

ef44e4d

	if let Some(allocator_ref) = allocator.as_mut() {
	allocator_ref.init(
	PhyAddr::from_usize(ekernel as *const () as usize).ceil(),
	PhyAddr::from_usize(MEMORY_END as usize).floor(),
	);

feat(RV64): implement dynamic memory/cpu decider, timer and interrupt controller #659

Are you sure you want to change the base?

feat(RV64): implement dynamic memory/cpu decider, timer and interrupt controller #659

Conversation

PeterWrighten commented Nov 11, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

How was this PR tested?

Uh oh!

PeterWrighten left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull Request Overview

Reviewed Changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

ytakano Nov 20, 2025

Choose a reason for hiding this comment

Uh oh!

ytakano commented Nov 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

PeterWrighten commented Nov 20, 2025

Uh oh!

ytakano commented Nov 21, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

PeterWrighten commented Nov 11, 2025 •

edited

Loading

ytakano commented Nov 20, 2025 •

edited

Loading