v0.10.4: GUI Bug Fixes + VirtIO GPU Acceleration

VeridianOS v0.10.4 -- GUI Bug Fixes + VirtIO GPU Acceleration

Summary

Fixes 5 GUI bugs discovered during interactive QEMU testing and wires the VirtIO GPU driver (fully implemented in Phase 7 Wave 1 but never connected to the renderer) into the desktop compositing pipeline for hardware-accelerated 2D framebuffer output.

Bug Fixes

1. System Monitor Shows All Zeros

Root cause: Performance counter functions (perf::count_syscall(), count_context_switch(), count_page_fault()) existed as atomic increment stubs but were never called from any kernel code path. Additionally, count_interrupt() didn't exist at all despite INTERRUPT_COUNT: AtomicU64 being declared.

Fix: Wired counters into hot paths:

• perf::count_syscall() at handle_syscall() entry -- counts every syscall dispatch
• perf::count_context_switch() in scheduler switch_to() -- counts actual task switches
• perf::count_page_fault() at page fault handler entry (before CR2 read)
• Added perf::count_interrupt() and wired into PIC timer (vector 32), APIC timer (vector 48), and keyboard (IRQ1) handlers

All use AtomicU64::fetch_add(1, Relaxed) -- zero-overhead, safe from any context including interrupt handlers.

2. Settings Window Is Blank

Root cause: render_all_apps() called render_placeholder_app("Settings", 0x2d3436) which draws only a solid background + centered title. The fully-implemented SettingsApp (sidebar navigation, 5 content panels, interactive fields) was never invoked.

Fix: Added render_to_u8_buffer() to SettingsApp that renders the complete UI directly to a BGRA byte buffer. Refactored existing render_to_buffer() to delegate to it. Added SettingsApp instance to DesktopState and replaced placeholder call.

3. Panel Clock Shows Wrong Date/Time

Root cause: Clock derived from read_hw_timestamp() (TSC ticks / 1GHz) -- starts at 00:00 on boot with fake date math (days % 28 for day-of-month). No CMOS RTC driver existed.

Fix: New CMOS MC146818 RTC driver (kernel/src/arch/x86_64/rtc.rs, 133 lines):

• Reads registers via I/O ports 0x70/0x71 with BCD-to-binary conversion
• Handles 12/24-hour format, century register (0x32), update-in-progress wait
• init(): Snapshots boot-time RTC to BOOT_EPOCH: AtomicU64 + captures TSC baseline
• current_epoch_secs(): BOOT_EPOCH + (now_tsc - boot_tsc) / 1GHz
• Panel clock rewritten with proper Unix epoch decomposition (leap years, month lengths, day-of-week via (days + 4) % 7)

4. Taskbar Click Doesn't Switch Focus

Root cause: panel.update_buttons() ran only every N frames, so the button hit-test list was stale when click events arrived -- window IDs and positions didn't match actual WM state.

Fix: Force panel.update_buttons() immediately before handle_click() in the panel click event path.

5. GUI Is Sluggish

Root causes: Apps rendered every 4th frame (effective 15 FPS), panel updated every 60th frame, spin-loop frame pacing at 50,000 iterations.

Fix: Removed is_multiple_of(4) app render skip (every frame now), reduced panel interval from 60 to 10 frames, reduced spin loop from 50,000 to 5,000 iterations.

VirtIO GPU Hardware-Accelerated Framebuffer Blit

The VirtIO GPU driver (kernel/src/drivers/virtio_gpu.rs, ~1800 lines) was fully implemented in Phase 7 Wave 1 with 2D resource management, BGRX8888 backing buffer, and virtqueue transport, but was never called from the desktop renderer. The desktop wrote directly to the UEFI GOP MMIO framebuffer via per-row copy_nonoverlapping (uncached memory, ~200-1000 MB/s).

New try_gpu_blit() function:

1. Checks virtio_gpu::is_available() -- returns false if no VirtIO GPU (QEMU -vga std)
2. Copies compositor back-buffer to GPU DMA backing store via copy_from_slice() (~2-10 GB/s)
3. Issues TRANSFER_TO_HOST_2D + RESOURCE_FLUSH via virtqueue (lightweight DMA commands)
4. Falls back to existing UEFI GOP MMIO path when VirtIO GPU not detected

Format compatibility: compositor XRGB8888 and VirtIO GPU BGRX8888 have identical byte layout -- no conversion needed.

Files Changed

File	Type	Description
kernel/src/perf/mod.rs	Modified	Add count_interrupt() function
kernel/src/syscall/mod.rs	Modified	Wire count_syscall()
kernel/src/sched/scheduler.rs	Modified	Wire count_context_switch()
kernel/src/arch/x86_64/idt.rs	Modified	Wire count_page_fault() + count_interrupt()
kernel/src/desktop/settings.rs	Modified	Add render_to_u8_buffer(), refactor render_to_buffer()
kernel/src/desktop/renderer.rs	Modified	Settings rendering, VirtIO GPU blit, render skip removal, panel interval, taskbar fix
kernel/src/arch/x86_64/rtc.rs	New	CMOS MC146818 RTC driver (133 lines)
kernel/src/arch/x86_64/mod.rs	Modified	Add pub mod rtc
kernel/src/bootstrap.rs	Modified	Add rtc::init() call
kernel/src/desktop/panel.rs	Modified	RTC-based wall-clock time, epoch-to-date conversion
Cargo.toml	Modified	Version 0.10.3 → 0.10.4
kernel/src/fs/mod.rs	Modified	Version in os-release
kernel/src/services/shell/commands.rs	Modified	Version in uname

13 files (1 new), +329/-128 lines

Build Verification

• cargo fmt --all -- --check: Clean
• cargo clippy --target x86_64-unknown-none: Zero warnings
• cargo clippy --target aarch64-unknown-none: Zero warnings
• cargo clippy --target riscv64gc-unknown-none-elf: Zero warnings
• ./build-kernel.sh all dev: All 3 architectures successful

Full Changelog

See CHANGELOG.md for complete release history.