# Repartir: Distributed Computing Primitives for Rust

**Version:** 2.0.0-draft (Complete Sovereign Stack)
**Status:** DRAFT - Iteration 4 (Pepita Unified Architecture)
**Last Updated:** 2026-01-04
**Quality Framework:** Iron Lotus + Certeza

## Executive Summary

Repartir is a **Sovereign AI-grade** pure Rust distributed computing stack built on **pepita**—a comprehensive kernel-to-userspace framework that provides:

1. **Kernel Interfaces**: Pure Rust bindings for Linux kernel subsystems (ublk, io_uring, blk-mq)
2. **zram**: Compressed RAM block device for memory-efficient workloads
3. **Lightweight Virtualization**: KVM-based microVM runtime (Firecracker-inspired)
4. **SIMD Compute**: Native trueno integration for vectorized operations
5. **GPU Compute**: wgpu-based shader execution (pure Rust, no CUDA)
6. **Distributed Execution**: Work-stealing scheduler across CPU, GPU, VM, and remote backends

**This is a complete Docker/Lambda/Kubernetes replacement** that organizations can fully own, audit, and control—100% pure Rust with zero C/C++ dependencies.

**Key Differentiators:**
- **100% Pure Rust**: Zero C/C++ dependencies, complete auditability
- **Kernel-to-Userspace**: From io_uring to microVMs in one coherent stack
- **zram Compression**: 2-4x memory efficiency for workloads
- **MicroVM Isolation**: Hardware-enforced security (KVM/EPT)
- **Sub-100ms Cold Start**: Faster than Docker, more secure than containers
- **SIMD Native**: trueno integration for AVX-512/NEON acceleration
- **GPU Compute**: wgpu for cross-platform shader execution
- **Serverless-Native**: Lambda-compatible execution model
- **Work-Stealing Scheduler**: Blumofe-Leiserson algorithm
- **Iron Lotus Quality**: Toyota Way engineering discipline

## 1. Pepita Architecture Overview

Pepita is the foundational crate that implements all low-level and high-level components of the Sovereign AI stack.

### 1.1 Layer Architecture

```
┌─────────────────────────────────────────────────────────────────────────────┐
│                         User Applications                                   │
│                    (repartir high-level API)                                │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  ┌─────────────────────────────────────────────────────────────────────┐   │
│  │                    Pepita Userspace Layer                            │   │
│  │  ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐  │   │
│  │  │   Pool   │ │ Scheduler│ │ Executor │ │   Task   │ │Transport │  │   │
│  │  │  (API)   │ │(WorkSteal│ │ Registry │ │  Types   │ │ Protocol │  │   │
│  │  └──────────┘ └──────────┘ └──────────┘ └──────────┘ └──────────┘  │   │
│  └─────────────────────────────────────────────────────────────────────┘   │
│                                                                             │
│  ┌─────────────────────────────────────────────────────────────────────┐   │
│  │                    Pepita Execution Backends                         │   │
│  │  ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐  │   │
│  │  │   CPU    │ │   GPU    │ │  MicroVM │ │  Remote  │ │   SIMD   │  │   │
│  │  │ Executor │ │ (wgpu)   │ │  (KVM)   │ │ (TCP/TLS)│ │ (trueno) │  │   │
│  │  └──────────┘ └──────────┘ └──────────┘ └──────────┘ └──────────┘  │   │
│  └─────────────────────────────────────────────────────────────────────┘   │
│                                                                             │
│  ┌─────────────────────────────────────────────────────────────────────┐   │
│  │                    Pepita Virtualization Layer                       │   │
│  │  ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐  │   │
│  │  │   VMM    │ │  vCPU    │ │  virtio  │ │  vsock   │ │  Jailer  │  │   │
│  │  │ Manager  │ │ Manager  │ │ Devices  │ │ Channel  │ │ Security │  │   │
│  │  └──────────┘ └──────────┘ └──────────┘ └──────────┘ └──────────┘  │   │
│  └─────────────────────────────────────────────────────────────────────┘   │
│                                                                             │
│  ┌─────────────────────────────────────────────────────────────────────┐   │
│  │                    Pepita Kernel Interface Layer                     │   │
│  │  ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐  │   │
│  │  │  io_uring│ │   ublk   │ │  blk_mq  │ │   zram   │ │  memory  │  │   │
│  │  │ AsyncI/O │ │ UserBlk  │ │ MultiQ   │ │ CompRAM  │ │ DMA/Page │  │   │
│  │  └──────────┘ └──────────┘ └──────────┘ └──────────┘ └──────────┘  │   │
│  └─────────────────────────────────────────────────────────────────────┘   │
│                                                                             │
├─────────────────────────────────────────────────────────────────────────────┤
│                         Linux Kernel (KVM, io_uring)                        │
└─────────────────────────────────────────────────────────────────────────────┘
```

### 1.2 Module Organization

```
pepita/
├── src/
│   ├── lib.rs              # Crate root
│   │
│   ├── # === KERNEL INTERFACES (no_std compatible) ===
│   ├── io_uring.rs         # io_uring SQE/CQE structures
│   ├── ublk.rs             # Userspace block device
│   ├── blk_mq.rs           # Multi-queue block layer
│   ├── memory.rs           # DMA, page allocation, physical memory
│   ├── zram.rs             # Compressed RAM block device [NEW]
│   ├── error.rs            # Kernel error types
│   │
│   ├── # === VIRTUALIZATION (std required) ===
│   ├── vmm/
│   │   ├── mod.rs          # VMM module root [NEW]
│   │   ├── kvm.rs          # KVM interface [NEW]
│   │   ├── vcpu.rs         # vCPU management [NEW]
│   │   ├── memory.rs       # Guest memory [NEW]
│   │   ├── virtio/
│   │   │   ├── mod.rs      # virtio device framework [NEW]
│   │   │   ├── block.rs    # virtio-blk [NEW]
│   │   │   ├── net.rs      # virtio-net [NEW]
│   │   │   └── vsock.rs    # virtio-vsock [NEW]
│   │   ├── jailer.rs       # Security sandbox [NEW]
│   │   └── snapshot.rs     # VM snapshots [NEW]
│   │
│   ├── # === COMPUTE BACKENDS (std required) ===
│   ├── simd.rs             # SIMD/trueno integration [NEW]
│   ├── gpu.rs              # GPU/wgpu compute [NEW]
│   │
│   ├── # === DISTRIBUTED COMPUTING (std required) ===
│   ├── scheduler.rs        # Work-stealing scheduler
│   ├── executor.rs         # Backend executors
│   ├── task.rs             # Task types
│   ├── pool.rs             # High-level Pool API
│   ├── transport.rs        # Message protocol
│   ├── fault.rs            # Fault tolerance
│   │
│   └── # === SERVERLESS (std required) ===
│       ├── serverless/
│       │   ├── mod.rs      # Serverless module [NEW]
│       │   ├── function.rs # Function model [NEW]
│       │   ├── trigger.rs  # Event triggers [NEW]
│       │   └── invoker.rs  # Function invoker [NEW]
```

### 1.3 Design Principles

1. **Pure Rust Everything**: Zero C/C++ FFI, zero binary blobs
2. **no_std Kernel Layer**: Core interfaces work without std for kernel module use
3. **Layered Architecture**: Each layer can be used independently
4. **Hardware Abstraction**: Same API across x86_64, aarch64
5. **Security by Default**: Jailer, seccomp, namespaces built-in

## 2. Kernel Interface Layer

### 2.1 io_uring (Async I/O)

Pure Rust implementation of Linux io_uring structures for high-performance async I/O.

```rust
/// io_uring Submission Queue Entry (SQE)
/// ABI-compatible with Linux kernel (64 bytes)
#[repr(C)]
pub struct IoUringSqe {
    pub opcode: u8,
    pub flags: u8,
    pub ioprio: u16,
    pub fd: i32,
    pub off: u64,
    pub addr: u64,
    pub len: u32,
    pub op_flags: u32,
    pub user_data: u64,
    pub buf_index: u16,
    pub personality: u16,
    pub splice_fd_in: i32,
    pub addr3: u64,
    pub __pad2: [u64; 1],
}

/// io_uring Completion Queue Entry (CQE)
/// ABI-compatible with Linux kernel (16 bytes)
#[repr(C)]
pub struct IoUringCqe {
    pub user_data: u64,
    pub res: i32,
    pub flags: u32,
}
```

### 2.2 ublk (Userspace Block Device)

Pure Rust interface to Linux ublk for implementing block devices in userspace.

```rust
/// ublk control command (32 bytes)
#[repr(C)]
pub struct UblkCtrlCmd {
    pub dev_id: u32,
    pub queue_id: u16,
    pub len: u16,
    pub addr: u64,
    pub data: [u64; 2],
}

/// ublk I/O descriptor (24 bytes)
#[repr(C)]
pub struct UblkIoDesc {
    pub flags: u32,
    pub nr_sectors: u32,
    pub start_sector: u64,
    pub addr: u64,
}
```

### 2.3 blk-mq (Multi-Queue Block Layer)

Pure Rust abstractions for Linux multi-queue block layer.

```rust
/// Block device request
#[repr(C)]
pub struct Request {
    pub op: RequestOp,
    pub sector: u64,
    pub nr_sectors: u32,
    pub tag: u32,
    pub data_ptr: u64,
    pub data_len: u32,
}

/// Tag set configuration
pub struct TagSetConfig {
    pub nr_hw_queues: u16,
    pub queue_depth: u16,
    pub numa_node: i32,
    pub cmd_size: u32,
}
```

### 2.4 zram (Compressed RAM Block Device) [NEW]

Pure Rust implementation of zram for memory-efficient compressed block storage.

```rust
/// zram compression algorithms (pure Rust implementations)
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ZramCompressor {
    /// LZ4 - fast compression/decompression
    Lz4,
    /// Zstd - high compression ratio
    Zstd,
    /// LZO - legacy compatibility
    Lzo,
    /// None - no compression (testing)
    None,
}

/// zram device configuration
#[derive(Debug, Clone)]
pub struct ZramConfig {
    /// Device size in bytes
    pub size_bytes: u64,
    /// Compression algorithm
    pub compressor: ZramCompressor,
    /// Maximum memory limit (None = 50% of size)
    pub mem_limit: Option<u64>,
    /// Number of compression streams (parallel compression)
    pub num_streams: u32,
    /// Enable memory tracking
    pub track_stats: bool,
}

impl Default for ZramConfig {
    fn default() -> Self {
        Self {
            size_bytes: 4 * 1024 * 1024 * 1024, // 4 GiB
            compressor: ZramCompressor::Lz4,
            mem_limit: None,
            num_streams: 4,
            track_stats: true,
        }
    }
}

/// zram device statistics
#[derive(Debug, Clone, Default)]
pub struct ZramStats {
    /// Uncompressed data size
    pub orig_data_size: u64,
    /// Compressed data size
    pub compr_data_size: u64,
    /// Memory used (including metadata)
    pub mem_used_total: u64,
    /// Number of pages stored
    pub pages_stored: u64,
    /// Number of same-page merges
    pub same_pages: u64,
    /// Number of huge pages
    pub huge_pages: u64,
    /// Compression ratio (orig/compr)
    pub compression_ratio: f64,
}

/// zram block device
pub struct ZramDevice {
    /// Configuration
    config: ZramConfig,
    /// Compressed page table
    page_table: PageTable,
    /// Compression streams (thread-local)
    streams: Vec<CompressionStream>,
    /// Statistics
    stats: AtomicStats,
}

impl ZramDevice {
    /// Create a new zram device
    pub fn new(config: ZramConfig) -> Result<Self> {
        let streams = (0..config.num_streams)
            .map(|_| CompressionStream::new(config.compressor))
            .collect::<Result<Vec<_>>>()?;

        Ok(Self {
            config,
            page_table: PageTable::new(),
            streams,
            stats: AtomicStats::default(),
        })
    }

    /// Read a page (decompress)
    pub fn read_page(&self, page_index: u64, buffer: &mut [u8; PAGE_SIZE]) -> Result<()> {
        let entry = self.page_table.get(page_index)?;

        match entry {
            PageEntry::Compressed { data, orig_size } => {
                let stream = self.get_stream();
                stream.decompress(data, buffer, orig_size)?;
            }
            PageEntry::Zero => {
                buffer.fill(0);
            }
            PageEntry::Same { value } => {
                buffer.fill(value);
            }
        }

        Ok(())
    }

    /// Write a page (compress)
    pub fn write_page(&self, page_index: u64, data: &[u8; PAGE_SIZE]) -> Result<()> {
        // Check for zero page
        if data.iter().all(|&b| b == 0) {
            self.page_table.set(page_index, PageEntry::Zero);
            self.stats.same_pages.fetch_add(1, Ordering::Relaxed);
            return Ok(());
        }

        // Check for same-filled page
        if let Some(value) = Self::check_same_filled(data) {
            self.page_table.set(page_index, PageEntry::Same { value });
            self.stats.same_pages.fetch_add(1, Ordering::Relaxed);
            return Ok(());
        }

        // Compress
        let stream = self.get_stream();
        let compressed = stream.compress(data)?;

        // Check if compression is worthwhile
        if compressed.len() >= PAGE_SIZE - 64 {
            // Store uncompressed
            self.page_table.set(page_index, PageEntry::Uncompressed {
                data: data.to_vec(),
            });
        } else {
            self.page_table.set(page_index, PageEntry::Compressed {
                data: compressed,
                orig_size: PAGE_SIZE as u32,
            });
        }

        self.stats.update(data.len(), compressed.len());
        Ok(())
    }

    /// Get device statistics
    pub fn stats(&self) -> ZramStats {
        self.stats.snapshot()
    }
}

/// Compression stream (thread-local for parallel compression)
pub struct CompressionStream {
    compressor: ZramCompressor,
    compress_buffer: Vec<u8>,
    decompress_buffer: Vec<u8>,
}

impl CompressionStream {
    /// Compress data
    pub fn compress(&mut self, input: &[u8]) -> Result<Vec<u8>> {
        match self.compressor {
            ZramCompressor::Lz4 => self.compress_lz4(input),
            ZramCompressor::Zstd => self.compress_zstd(input),
            ZramCompressor::Lzo => self.compress_lzo(input),
            ZramCompressor::None => Ok(input.to_vec()),
        }
    }

    /// Decompress data
    pub fn decompress(&mut self, input: &[u8], output: &mut [u8], orig_size: u32) -> Result<()> {
        match self.compressor {
            ZramCompressor::Lz4 => self.decompress_lz4(input, output, orig_size),
            ZramCompressor::Zstd => self.decompress_zstd(input, output, orig_size),
            ZramCompressor::Lzo => self.decompress_lzo(input, output, orig_size),
            ZramCompressor::None => {
                output[..input.len()].copy_from_slice(input);
                Ok(())
            }
        }
    }

    // Pure Rust LZ4 implementation
    fn compress_lz4(&mut self, input: &[u8]) -> Result<Vec<u8>> {
        // LZ4 block compression algorithm (pure Rust)
        // ...
    }

    fn decompress_lz4(&mut self, input: &[u8], output: &mut [u8], _orig_size: u32) -> Result<()> {
        // LZ4 block decompression algorithm (pure Rust)
        // ...
    }
}
```

### 2.5 Memory Management

Pure Rust physical and virtual memory management.

```rust
/// Physical address (strongly typed)
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct PhysAddr(u64);

/// Virtual address (strongly typed)
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct VirtAddr(u64);

/// Page Frame Number
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(transparent)]
pub struct Pfn(u64);

/// DMA buffer for device I/O
pub struct DmaBuffer {
    virt_addr: VirtAddr,
    phys_addr: PhysAddr,
    size: usize,
    direction: DmaDirection,
}
```

## 3. Virtualization Layer (MicroVM)

### 3.1 VMM Architecture

Pure Rust Virtual Machine Monitor inspired by Firecracker.

```rust
/// Repartir VMM - Pure Rust Virtual Machine Monitor
pub struct Vmm {
    /// KVM system interface
    kvm: KvmSystem,
    /// VM instance
    vm: Option<Vm>,
    /// Event loop
    event_loop: EventLoop,
}

impl Vmm {
    /// Create a new VMM
    pub fn new() -> Result<Self> {
        let kvm = KvmSystem::open()?;
        kvm.check_extension(KvmCap::Irqchip)?;
        kvm.check_extension(KvmCap::UserMemory)?;

        Ok(Self {
            kvm,
            vm: None,
            event_loop: EventLoop::new()?,
        })
    }

    /// Create and boot a microVM
    pub fn create_vm(&mut self, config: VmConfig) -> Result<VmHandle> {
        let vm = Vm::new(&self.kvm, config)?;
        let handle = vm.handle();
        self.vm = Some(vm);
        Ok(handle)
    }

    /// Run the VM event loop
    pub fn run(&mut self) -> Result<VmExit> {
        let vm = self.vm.as_mut().ok_or(Error::NoVm)?;
        vm.run(&mut self.event_loop)
    }
}
```

### 3.2 KVM Interface

Pure Rust bindings to Linux KVM (no kvm-ioctls crate, first principles).

```rust
/// KVM system file descriptor wrapper
pub struct KvmSystem {
    fd: OwnedFd,
}

impl KvmSystem {
    /// Open /dev/kvm
    pub fn open() -> Result<Self> {
        let fd = unsafe {
            let raw = libc::open(c"/dev/kvm".as_ptr(), libc::O_RDWR | libc::O_CLOEXEC);
            if raw < 0 {
                return Err(Error::KvmOpen);
            }
            OwnedFd::from_raw_fd(raw)
        };

        Ok(Self { fd })
    }

    /// Check KVM API version
    pub fn api_version(&self) -> Result<i32> {
        // KVM_GET_API_VERSION = 0xAE00
        let version = unsafe { kvm_ioctl(self.fd.as_raw_fd(), 0xAE00, 0)? };
        Ok(version as i32)
    }

    /// Create a VM
    pub fn create_vm(&self) -> Result<VmFd> {
        // KVM_CREATE_VM = 0xAE01
        let vm_fd = unsafe { kvm_ioctl(self.fd.as_raw_fd(), 0xAE01, 0)? };
        Ok(VmFd::new(vm_fd))
    }

    /// Check capability
    pub fn check_extension(&self, cap: KvmCap) -> Result<bool> {
        // KVM_CHECK_EXTENSION = 0xAE03
        let result = unsafe { kvm_ioctl(self.fd.as_raw_fd(), 0xAE03, cap as u64)? };
        Ok(result > 0)
    }
}

/// KVM capabilities
#[repr(u32)]
pub enum KvmCap {
    Irqchip = 0,
    Hlt = 1,
    UserMemory = 3,
    SetTssAddr = 4,
    ExtCpuid = 7,
    Pit2 = 33,
    IrqRouting = 25,
    Msi = 38,
}

/// VM file descriptor
pub struct VmFd {
    fd: OwnedFd,
}

impl VmFd {
    /// Create a vCPU
    pub fn create_vcpu(&self, id: u32) -> Result<VcpuFd> {
        // KVM_CREATE_VCPU = 0xAE41
        let vcpu_fd = unsafe { kvm_ioctl(self.fd.as_raw_fd(), 0xAE41, id as u64)? };
        Ok(VcpuFd::new(vcpu_fd, id))
    }

    /// Set user memory region
    pub fn set_user_memory_region(&self, region: &KvmUserspaceMemoryRegion) -> Result<()> {
        // KVM_SET_USER_MEMORY_REGION = 0x4020AE46
        unsafe {
            kvm_ioctl(self.fd.as_raw_fd(), 0x4020AE46, region as *const _ as u64)?;
        }
        Ok(())
    }

    /// Create interrupt controller
    pub fn create_irqchip(&self) -> Result<()> {
        // KVM_CREATE_IRQCHIP = 0xAE60
        unsafe { kvm_ioctl(self.fd.as_raw_fd(), 0xAE60, 0)?; }
        Ok(())
    }

    /// Create PIT2
    pub fn create_pit2(&self) -> Result<()> {
        let config = KvmPitConfig::default();
        // KVM_CREATE_PIT2 = 0x4040AE77
        unsafe {
            kvm_ioctl(self.fd.as_raw_fd(), 0x4040AE77, &config as *const _ as u64)?;
        }
        Ok(())
    }
}

/// Memory region for KVM
#[repr(C)]
pub struct KvmUserspaceMemoryRegion {
    pub slot: u32,
    pub flags: u32,
    pub guest_phys_addr: u64,
    pub memory_size: u64,
    pub userspace_addr: u64,
}
```

### 3.3 vCPU Management

```rust
/// vCPU file descriptor
pub struct VcpuFd {
    fd: OwnedFd,
    id: u32,
    run: *mut KvmRun,
}

impl VcpuFd {
    /// Run the vCPU until exit
    pub fn run(&mut self) -> Result<VcpuExit> {
        // KVM_RUN = 0xAE80
        unsafe {
            let ret = libc::ioctl(self.fd.as_raw_fd(), 0xAE80);
            if ret < 0 {
                return Err(Error::VcpuRun(std::io::Error::last_os_error()));
            }
        }

        // Parse exit reason
        let exit_reason = unsafe { (*self.run).exit_reason };
        self.parse_exit(exit_reason)
    }

    /// Set registers
    pub fn set_regs(&self, regs: &KvmRegs) -> Result<()> {
        // KVM_SET_REGS = 0x4090AE82
        unsafe {
            kvm_ioctl(self.fd.as_raw_fd(), 0x4090AE82, regs as *const _ as u64)?;
        }
        Ok(())
    }

    /// Set special registers
    pub fn set_sregs(&self, sregs: &KvmSregs) -> Result<()> {
        // KVM_SET_SREGS = 0x4138AE84
        unsafe {
            kvm_ioctl(self.fd.as_raw_fd(), 0x4138AE84, sregs as *const _ as u64)?;
        }
        Ok(())
    }

    fn parse_exit(&self, reason: u32) -> Result<VcpuExit> {
        match reason {
            0 => Ok(VcpuExit::Unknown),
            2 => {
                let io = unsafe { &(*self.run).io };
                Ok(VcpuExit::Io {
                    direction: if io.direction == 0 { IoDirection::In } else { IoDirection::Out },
                    port: io.port,
                    size: io.size as usize,
                    count: io.count as usize,
                })
            }
            5 => Ok(VcpuExit::Hlt),
            6 => {
                let mmio = unsafe { &(*self.run).mmio };
                Ok(VcpuExit::Mmio {
                    addr: mmio.phys_addr,
                    data: mmio.data,
                    len: mmio.len as usize,
                    is_write: mmio.is_write != 0,
                })
            }
            17 => Ok(VcpuExit::Shutdown),
            _ => Ok(VcpuExit::Unknown),
        }
    }
}

/// vCPU exit reasons
#[derive(Debug)]
pub enum VcpuExit {
    Unknown,
    Io {
        direction: IoDirection,
        port: u16,
        size: usize,
        count: usize,
    },
    Mmio {
        addr: u64,
        data: [u8; 8],
        len: usize,
        is_write: bool,
    },
    Hlt,
    Shutdown,
}
```

### 3.4 Guest Memory

```rust
/// Guest memory map
pub struct GuestMemory {
    /// Memory regions
    regions: Vec<MemoryRegion>,
    /// Total size
    total_size: u64,
}

impl GuestMemory {
    /// Create guest memory with given size
    pub fn new(size_mib: u32) -> Result<Self> {
        let size = (size_mib as u64) * 1024 * 1024;

        // Allocate with mmap
        let ptr = unsafe {
            libc::mmap(
                std::ptr::null_mut(),
                size as usize,
                libc::PROT_READ | libc::PROT_WRITE,
                libc::MAP_PRIVATE | libc::MAP_ANONYMOUS | libc::MAP_NORESERVE,
                -1,
                0,
            )
        };

        if ptr == libc::MAP_FAILED {
            return Err(Error::MemoryAllocation);
        }

        let region = MemoryRegion {
            guest_base: 0,
            size,
            host_addr: ptr as u64,
        };

        Ok(Self {
            regions: vec![region],
            total_size: size,
        })
    }

    /// Load data into guest memory
    pub fn load(&mut self, guest_addr: u64, data: &[u8]) -> Result<()> {
        let host_addr = self.translate(guest_addr)?;
        unsafe {
            std::ptr::copy_nonoverlapping(
                data.as_ptr(),
                host_addr as *mut u8,
                data.len(),
            );
        }
        Ok(())
    }

    /// Translate guest address to host address
    pub fn translate(&self, guest_addr: u64) -> Result<u64> {
        for region in &self.regions {
            if guest_addr >= region.guest_base
                && guest_addr < region.guest_base + region.size
            {
                let offset = guest_addr - region.guest_base;
                return Ok(region.host_addr + offset);
            }
        }
        Err(Error::InvalidGuestAddress(guest_addr))
    }
}
```

### 3.5 virtio Devices

Pure Rust virtio device implementations.

```rust
/// virtio device trait
pub trait VirtioDevice: Send {
    /// Device type
    fn device_type(&self) -> u32;

    /// Queue count
    fn queue_count(&self) -> usize;

    /// Activate the device
    fn activate(&mut self, queues: Vec<Queue>) -> Result<()>;

    /// Handle queue notification
    fn handle_queue(&mut self, queue_index: usize) -> Result<()>;
}

/// virtio-vsock for host-guest communication
pub struct VirtioVsock {
    /// CID (Context ID) for this VM
    cid: u64,
    /// Receive queue
    rx_queue: Option<Queue>,
    /// Transmit queue
    tx_queue: Option<Queue>,
    /// Event queue
    event_queue: Option<Queue>,
    /// Connection state
    connections: HashMap<VsockAddr, VsockConnection>,
}

impl VirtioVsock {
    pub fn new(cid: u64) -> Self {
        Self {
            cid,
            rx_queue: None,
            tx_queue: None,
            event_queue: None,
            connections: HashMap::new(),
        }
    }

    /// Send data to guest
    pub fn send(&mut self, port: u32, data: &[u8]) -> Result<()> {
        let tx_queue = self.tx_queue.as_mut().ok_or(Error::NotActivated)?;
        // Write to virtqueue
        tx_queue.add_buffer(data)?;
        tx_queue.notify()?;
        Ok(())
    }

    /// Receive data from guest
    pub fn recv(&mut self, port: u32) -> Result<Vec<u8>> {
        let rx_queue = self.rx_queue.as_mut().ok_or(Error::NotActivated)?;
        rx_queue.pop_buffer()
    }
}

impl VirtioDevice for VirtioVsock {
    fn device_type(&self) -> u32 { 19 } // VIRTIO_ID_VSOCK

    fn queue_count(&self) -> usize { 3 } // rx, tx, event

    fn activate(&mut self, mut queues: Vec<Queue>) -> Result<()> {
        self.event_queue = queues.pop();
        self.tx_queue = queues.pop();
        self.rx_queue = queues.pop();
        Ok(())
    }

    fn handle_queue(&mut self, queue_index: usize) -> Result<()> {
        match queue_index {
            0 => self.handle_rx(),
            1 => self.handle_tx(),
            2 => self.handle_event(),
            _ => Err(Error::InvalidQueue),
        }
    }
}

/// virtio-blk for block devices
pub struct VirtioBlock {
    /// Backing file/device
    backend: BlockBackend,
    /// Request queue
    queue: Option<Queue>,
    /// Read-only flag
    read_only: bool,
}

impl VirtioDevice for VirtioBlock {
    fn device_type(&self) -> u32 { 2 } // VIRTIO_ID_BLOCK
    fn queue_count(&self) -> usize { 1 }

    fn activate(&mut self, mut queues: Vec<Queue>) -> Result<()> {
        self.queue = queues.pop();
        Ok(())
    }

    fn handle_queue(&mut self, _queue_index: usize) -> Result<()> {
        let queue = self.queue.as_mut().ok_or(Error::NotActivated)?;

        while let Some(desc) = queue.pop_descriptor()? {
            let request = self.parse_request(&desc)?;

            match request.op {
                BlockOp::Read => {
                    let data = self.backend.read(request.sector, request.count)?;
                    queue.write_response(&desc, &data, 0)?;
                }
                BlockOp::Write => {
                    self.backend.write(request.sector, &request.data)?;
                    queue.write_response(&desc, &[], 0)?;
                }
                BlockOp::Flush => {
                    self.backend.flush()?;
                    queue.write_response(&desc, &[], 0)?;
                }
            }
        }

        Ok(())
    }
}
```

### 3.6 Jailer (Security Sandbox)

```rust
/// Jailer for production microVM deployment
pub struct Jailer {
    /// Chroot base directory
    chroot_base: PathBuf,
    /// Unprivileged UID
    uid: u32,
    /// Unprivileged GID
    gid: u32,
    /// Cgroup path
    cgroup_path: PathBuf,
}

impl Jailer {
    /// Create a jailed VMM process
    pub fn jail(&self, vmm_config: &VmConfig) -> Result<JailedVmm> {
        // 1. Create unique chroot directory
        let chroot_dir = self.setup_chroot(vmm_config)?;

        // 2. Setup cgroup
        self.setup_cgroup(vmm_config)?;

        // 3. Fork and jail
        let pid = unsafe { libc::fork() };

        if pid == 0 {
            // Child process

            // Setup namespaces
            self.setup_namespaces()?;

            // Chroot
            self.do_chroot(&chroot_dir)?;

            // Drop privileges
            self.drop_privileges()?;

            // Apply seccomp filter
            self.apply_seccomp()?;

            // Now run the VMM
            // This never returns
            self.run_vmm(vmm_config)?;
        }

        Ok(JailedVmm { pid: pid as u32 })
    }

    fn setup_namespaces(&self) -> Result<()> {
        // Create new namespaces
        unsafe {
            // CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWNET | CLONE_NEWUSER
            let flags = 0x20000 | 0x20000000 | 0x40000000 | 0x10000000;
            if libc::unshare(flags) != 0 {
                return Err(Error::NamespaceSetup);
            }
        }
        Ok(())
    }

    fn apply_seccomp(&self) -> Result<()> {
        // Seccomp BPF filter - whitelist approach
        let filter = SeccompFilter::new()
            // Allow only essential syscalls
            .allow(Syscall::Read)
            .allow(Syscall::Write)
            .allow(Syscall::Ioctl)      // For KVM
            .allow(Syscall::Mmap)
            .allow(Syscall::Munmap)
            .allow(Syscall::Exit)
            .allow(Syscall::ExitGroup)
            .allow(Syscall::Futex)
            .allow(Syscall::EpollWait)
            .allow(Syscall::EpollCtl)
            .default_action(SeccompAction::Kill)
            .build()?;

        filter.apply()?;
        Ok(())
    }
}
```

## 4. SIMD Compute Layer (trueno Integration)

### 4.1 SIMD Detection and Dispatch

```rust
/// SIMD feature detection (runtime)
#[derive(Debug, Clone, Copy)]
pub struct SimdCapabilities {
    /// SSE4.1 support
    pub sse41: bool,
    /// SSE4.2 support
    pub sse42: bool,
    /// AVX support
    pub avx: bool,
    /// AVX2 support
    pub avx2: bool,
    /// AVX-512 support
    pub avx512f: bool,
    /// AVX-512 Vector Length Extensions
    pub avx512vl: bool,
    /// ARM NEON support
    pub neon: bool,
    /// ARM SVE support
    pub sve: bool,
}

impl SimdCapabilities {
    /// Detect CPU SIMD capabilities
    pub fn detect() -> Self {
        #[cfg(target_arch = "x86_64")]
        {
            Self {
                sse41: is_x86_feature_detected!("sse4.1"),
                sse42: is_x86_feature_detected!("sse4.2"),
                avx: is_x86_feature_detected!("avx"),
                avx2: is_x86_feature_detected!("avx2"),
                avx512f: is_x86_feature_detected!("avx512f"),
                avx512vl: is_x86_feature_detected!("avx512vl"),
                neon: false,
                sve: false,
            }
        }

        #[cfg(target_arch = "aarch64")]
        {
            Self {
                sse41: false,
                sse42: false,
                avx: false,
                avx2: false,
                avx512f: false,
                avx512vl: false,
                neon: true, // Always available on aarch64
                sve: Self::detect_sve(),
            }
        }
    }

    /// Get best available vector width (in bits)
    pub fn best_vector_width(&self) -> u32 {
        if self.avx512f { 512 }
        else if self.avx2 || self.avx { 256 }
        else if self.sse42 || self.sse41 { 128 }
        else if self.sve { 2048 } // Variable, up to 2048
        else if self.neon { 128 }
        else { 64 } // Scalar fallback
    }
}

/// SIMD-accelerated operations
pub struct SimdOps {
    caps: SimdCapabilities,
}

impl SimdOps {
    pub fn new() -> Self {
        Self {
            caps: SimdCapabilities::detect(),
        }
    }

    /// Vector addition: c = a + b
    pub fn vadd_f32(&self, a: &[f32], b: &[f32], c: &mut [f32]) {
        assert_eq!(a.len(), b.len());
        assert_eq!(a.len(), c.len());

        #[cfg(target_arch = "x86_64")]
        {
            if self.caps.avx512f {
                unsafe { self.vadd_f32_avx512(a, b, c) }
            } else if self.caps.avx2 {
                unsafe { self.vadd_f32_avx2(a, b, c) }
            } else if self.caps.sse42 {
                unsafe { self.vadd_f32_sse(a, b, c) }
            } else {
                self.vadd_f32_scalar(a, b, c)
            }
        }

        #[cfg(target_arch = "aarch64")]
        {
            if self.caps.neon {
                unsafe { self.vadd_f32_neon(a, b, c) }
            } else {
                self.vadd_f32_scalar(a, b, c)
            }
        }
    }

    #[cfg(target_arch = "x86_64")]
    #[target_feature(enable = "avx512f")]
    unsafe fn vadd_f32_avx512(&self, a: &[f32], b: &[f32], c: &mut [f32]) {
        use std::arch::x86_64::*;

        let chunks = a.len() / 16;
        for i in 0..chunks {
            let offset = i * 16;
            let va = _mm512_loadu_ps(a.as_ptr().add(offset));
            let vb = _mm512_loadu_ps(b.as_ptr().add(offset));
            let vc = _mm512_add_ps(va, vb);
            _mm512_storeu_ps(c.as_mut_ptr().add(offset), vc);
        }

        // Handle remainder
        let remainder = a.len() % 16;
        if remainder > 0 {
            let start = chunks * 16;
            for i in start..a.len() {
                c[i] = a[i] + b[i];
            }
        }
    }

    #[cfg(target_arch = "x86_64")]
    #[target_feature(enable = "avx2")]
    unsafe fn vadd_f32_avx2(&self, a: &[f32], b: &[f32], c: &mut [f32]) {
        use std::arch::x86_64::*;

        let chunks = a.len() / 8;
        for i in 0..chunks {
            let offset = i * 8;
            let va = _mm256_loadu_ps(a.as_ptr().add(offset));
            let vb = _mm256_loadu_ps(b.as_ptr().add(offset));
            let vc = _mm256_add_ps(va, vb);
            _mm256_storeu_ps(c.as_mut_ptr().add(offset), vc);
        }

        // Handle remainder
        let start = chunks * 8;
        for i in start..a.len() {
            c[i] = a[i] + b[i];
        }
    }

    #[cfg(target_arch = "aarch64")]
    #[target_feature(enable = "neon")]
    unsafe fn vadd_f32_neon(&self, a: &[f32], b: &[f32], c: &mut [f32]) {
        use std::arch::aarch64::*;

        let chunks = a.len() / 4;
        for i in 0..chunks {
            let offset = i * 4;
            let va = vld1q_f32(a.as_ptr().add(offset));
            let vb = vld1q_f32(b.as_ptr().add(offset));
            let vc = vaddq_f32(va, vb);
            vst1q_f32(c.as_mut_ptr().add(offset), vc);
        }

        let start = chunks * 4;
        for i in start..a.len() {
            c[i] = a[i] + b[i];
        }
    }

    fn vadd_f32_scalar(&self, a: &[f32], b: &[f32], c: &mut [f32]) {
        for i in 0..a.len() {
            c[i] = a[i] + b[i];
        }
    }

    /// Matrix multiplication (C = A @ B)
    pub fn matmul_f32(
        &self,
        a: &[f32], // m x k
        b: &[f32], // k x n
        c: &mut [f32], // m x n
        m: usize,
        k: usize,
        n: usize,
    ) {
        // Use SIMD-accelerated GEMM with tiling
        const TILE_SIZE: usize = 64;

        // Zero output
        c.fill(0.0);

        // Tiled multiplication for cache efficiency
        for i0 in (0..m).step_by(TILE_SIZE) {
            for j0 in (0..n).step_by(TILE_SIZE) {
                for k0 in (0..k).step_by(TILE_SIZE) {
                    let i_end = (i0 + TILE_SIZE).min(m);
                    let j_end = (j0 + TILE_SIZE).min(n);
                    let k_end = (k0 + TILE_SIZE).min(k);

                    self.matmul_tile(a, b, c, i0, j0, k0, i_end, j_end, k_end, k, n);
                }
            }
        }
    }
}
```

### 4.2 trueno Integration

```rust
/// Integration with trueno crate for tensor operations
pub struct TruenoContext {
    /// SIMD capabilities
    simd: SimdOps,
    /// Memory pool for tensor allocation
    memory_pool: MemoryPool,
}

impl TruenoContext {
    /// Create shared tensor for cross-process/VM communication
    pub fn create_shared_tensor<T: TruenoScalar>(
        &self,
        shape: &[usize],
    ) -> Result<SharedTensor<T>> {
        let size = shape.iter().product::<usize>() * std::mem::size_of::<T>();

        // Allocate shared memory
        let shm = SharedMemory::create(size)?;

        Ok(SharedTensor {
            data: shm,
            shape: shape.to_vec(),
            _marker: PhantomData,
        })
    }

    /// SIMD-accelerated tensor addition
    pub fn add(&self, a: &Tensor<f32>, b: &Tensor<f32>) -> Tensor<f32> {
        assert_eq!(a.shape(), b.shape());

        let mut result = Tensor::zeros(a.shape());
        self.simd.vadd_f32(a.data(), b.data(), result.data_mut());
        result
    }

    /// SIMD-accelerated matrix multiply
    pub fn matmul(&self, a: &Tensor<f32>, b: &Tensor<f32>) -> Tensor<f32> {
        assert_eq!(a.shape().len(), 2);
        assert_eq!(b.shape().len(), 2);
        assert_eq!(a.shape()[1], b.shape()[0]);

        let m = a.shape()[0];
        let k = a.shape()[1];
        let n = b.shape()[1];

        let mut result = Tensor::zeros(&[m, n]);
        self.simd.matmul_f32(a.data(), b.data(), result.data_mut(), m, k, n);
        result
    }
}

/// Shared tensor for IPC
pub struct SharedTensor<T> {
    data: SharedMemory,
    shape: Vec<usize>,
    _marker: PhantomData<T>,
}

impl<T: TruenoScalar> SharedTensor<T> {
    /// Get immutable slice
    pub fn as_slice(&self) -> &[T] {
        unsafe {
            std::slice::from_raw_parts(
                self.data.ptr() as *const T,
                self.shape.iter().product(),
            )
        }
    }

    /// Get mutable slice
    pub fn as_slice_mut(&mut self) -> &mut [T] {
        unsafe {
            std::slice::from_raw_parts_mut(
                self.data.ptr() as *mut T,
                self.shape.iter().product(),
            )
        }
    }

    /// Share with a microVM
    pub fn share_with_vm(&self, vmm: &mut Vmm) -> Result<GuestTensorHandle> {
        vmm.map_shared_memory(&self.data)?;
        Ok(GuestTensorHandle {
            guest_addr: self.data.guest_addr(),
            shape: self.shape.clone(),
        })
    }
}
```

## 5. GPU Compute Layer (wgpu)

### 5.1 GPU Device Management

```rust
/// GPU compute context (pure Rust via wgpu)
pub struct GpuContext {
    /// wgpu instance
    instance: wgpu::Instance,
    /// Available adapters
    adapters: Vec<GpuAdapter>,
    /// Active device
    device: Option<ActiveDevice>,
}

/// GPU adapter info
pub struct GpuAdapter {
    /// Adapter handle
    adapter: wgpu::Adapter,
    /// Device info
    info: wgpu::AdapterInfo,
    /// Limits
    limits: wgpu::Limits,
}

/// Active GPU device
pub struct ActiveDevice {
    device: wgpu::Device,
    queue: wgpu::Queue,
}

impl GpuContext {
    /// Create GPU context and enumerate devices
    pub async fn new() -> Result<Self> {
        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
            backends: wgpu::Backends::VULKAN | wgpu::Backends::METAL,
            ..Default::default()
        });

        let adapters: Vec<GpuAdapter> = instance
            .enumerate_adapters(wgpu::Backends::all())
            .into_iter()
            .map(|adapter| {
                let info = adapter.get_info();
                let limits = adapter.limits();
                GpuAdapter { adapter, info, limits }
            })
            .collect();

        Ok(Self {
            instance,
            adapters,
            device: None,
        })
    }

    /// Get best GPU (prefer discrete)
    pub fn best_adapter(&self) -> Option<&GpuAdapter> {
        // Prefer discrete GPU
        self.adapters.iter()
            .find(|a| a.info.device_type == wgpu::DeviceType::DiscreteGpu)
            .or_else(|| self.adapters.first())
    }

    /// Initialize device
    pub async fn init_device(&mut self, adapter_index: usize) -> Result<()> {
        let adapter = &self.adapters[adapter_index];

        let (device, queue) = adapter.adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    label: Some("pepita-gpu"),
                    required_features: wgpu::Features::PUSH_CONSTANTS,
                    required_limits: wgpu::Limits::default(),
                    memory_hints: wgpu::MemoryHints::Performance,
                },
                None,
            )
            .await?;

        self.device = Some(ActiveDevice { device, queue });
        Ok(())
    }
}
```

### 5.2 Compute Shader Execution

```rust
/// GPU compute shader executor
pub struct GpuExecutor {
    context: GpuContext,
    /// Compiled shaders cache
    shader_cache: HashMap<u64, CompiledShader>,
}

/// Compiled compute shader
pub struct CompiledShader {
    module: wgpu::ShaderModule,
    pipeline: wgpu::ComputePipeline,
    bind_group_layout: wgpu::BindGroupLayout,
}

impl GpuExecutor {
    /// Execute a compute shader
    pub async fn execute(
        &self,
        shader: &ComputeShader,
        inputs: &[GpuBuffer],
        outputs: &mut [GpuBuffer],
        workgroups: (u32, u32, u32),
    ) -> Result<()> {
        let device = self.context.device.as_ref()
            .ok_or(Error::NoGpuDevice)?;

        // Get or compile shader
        let compiled = self.get_or_compile(shader)?;

        // Create bind group
        let bind_group = self.create_bind_group(&compiled, inputs, outputs)?;

        // Create command encoder
        let mut encoder = device.device.create_command_encoder(
            &wgpu::CommandEncoderDescriptor {
                label: Some("compute_encoder"),
            }
        );

        // Dispatch compute
        {
            let mut pass = encoder.begin_compute_pass(
                &wgpu::ComputePassDescriptor {
                    label: Some("compute_pass"),
                    timestamp_writes: None,
                }
            );

            pass.set_pipeline(&compiled.pipeline);
            pass.set_bind_group(0, &bind_group, &[]);
            pass.dispatch_workgroups(workgroups.0, workgroups.1, workgroups.2);
        }

        // Submit
        device.queue.submit(std::iter::once(encoder.finish()));

        // Wait for completion
        device.device.poll(wgpu::Maintain::Wait);

        Ok(())
    }

    /// Create buffer
    pub fn create_buffer(&self, size: u64, usage: BufferUsage) -> Result<GpuBuffer> {
        let device = self.context.device.as_ref()
            .ok_or(Error::NoGpuDevice)?;

        let wgpu_usage = match usage {
            BufferUsage::Storage => wgpu::BufferUsages::STORAGE | wgpu::BufferUsages::COPY_DST | wgpu::BufferUsages::COPY_SRC,
            BufferUsage::Uniform => wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
            BufferUsage::Staging => wgpu::BufferUsages::MAP_READ | wgpu::BufferUsages::COPY_DST,
        };

        let buffer = device.device.create_buffer(&wgpu::BufferDescriptor {
            label: None,
            size,
            usage: wgpu_usage,
            mapped_at_creation: false,
        });

        Ok(GpuBuffer { buffer, size })
    }

    /// Upload data to GPU
    pub fn upload(&self, buffer: &GpuBuffer, data: &[u8]) -> Result<()> {
        let device = self.context.device.as_ref()
            .ok_or(Error::NoGpuDevice)?;

        device.queue.write_buffer(&buffer.buffer, 0, data);
        Ok(())
    }

    /// Download data from GPU
    pub async fn download(&self, buffer: &GpuBuffer) -> Result<Vec<u8>> {
        let device = self.context.device.as_ref()
            .ok_or(Error::NoGpuDevice)?;

        // Create staging buffer
        let staging = device.device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("staging"),
            size: buffer.size,
            usage: wgpu::BufferUsages::MAP_READ | wgpu::BufferUsages::COPY_DST,
            mapped_at_creation: false,
        });

        // Copy to staging
        let mut encoder = device.device.create_command_encoder(
            &wgpu::CommandEncoderDescriptor { label: None }
        );
        encoder.copy_buffer_to_buffer(&buffer.buffer, 0, &staging, 0, buffer.size);
        device.queue.submit(std::iter::once(encoder.finish()));

        // Map and read
        let slice = staging.slice(..);
        let (tx, rx) = std::sync::mpsc::channel();
        slice.map_async(wgpu::MapMode::Read, move |result| {
            tx.send(result).unwrap();
        });

        device.device.poll(wgpu::Maintain::Wait);
        rx.recv().unwrap()?;

        let data = slice.get_mapped_range().to_vec();
        staging.unmap();

        Ok(data)
    }
}

/// Compute shader definition
pub struct ComputeShader {
    /// WGSL source or SPIR-V bytecode
    pub source: ShaderSource,
    /// Entry point name
    pub entry_point: String,
}

pub enum ShaderSource {
    Wgsl(String),
    SpirV(Vec<u32>),
}

/// GPU buffer
pub struct GpuBuffer {
    buffer: wgpu::Buffer,
    size: u64,
}

pub enum BufferUsage {
    Storage,
    Uniform,
    Staging,
}
```

### 5.3 rust-gpu Integration

```rust
/// Compile Rust code to SPIR-V for GPU execution
pub struct RustGpuCompiler {
    /// Compiler cache
    cache: HashMap<PathBuf, Vec<u32>>,
}

impl RustGpuCompiler {
    /// Compile a Rust GPU kernel to SPIR-V
    pub fn compile(&mut self, crate_path: &Path) -> Result<Vec<u32>> {
        // Check cache
        if let Some(spirv) = self.cache.get(crate_path) {
            return Ok(spirv.clone());
        }

        // Use spirv-builder to compile
        let result = spirv_builder::SpirvBuilder::new(crate_path, "spirv-unknown-vulkan1.2")
            .capability(spirv_builder::Capability::Float64)
            .build()?;

        let spirv = std::fs::read(result.module.unwrap_single())?;
        let spirv_words: Vec<u32> = spirv
            .chunks_exact(4)
            .map(|chunk| u32::from_le_bytes([chunk[0], chunk[1], chunk[2], chunk[3]]))
            .collect();

        self.cache.insert(crate_path.to_owned(), spirv_words.clone());
        Ok(spirv_words)
    }
}
```

## 6. Distributed Computing Layer

(Existing scheduler, executor, pool, task, transport, fault modules - already implemented)

## 7. Serverless Layer

### 7.1 Function Model

```rust
/// Serverless function
pub struct Function {
    pub id: Uuid,
    pub name: String,
    pub runtime: Runtime,
    pub memory_mib: u32,
    pub timeout: Duration,
    pub env: HashMap<String, String>,
}

pub enum Runtime {
    /// Native Rust binary
    RustNative { binary_path: PathBuf },
    /// OCI container
    Container { image: String },
    /// trueno workload
    Trueno { workload: TruenoWorkload },
    /// GPU shader
    GpuShader { shader: ComputeShader },
}
```

### 7.2 Event Triggers

```rust
pub enum Trigger {
    Http { path: String, methods: Vec<Method> },
    Schedule { cron: String },
    Queue { queue_name: String },
    FileSystem { path: PathBuf, events: Vec<FsEvent> },
}
```

## 8. API Summary

```rust
use pepita::{
    // Kernel interfaces
    io_uring::{IoUringSqe, IoUringCqe},
    ublk::{UblkCtrlCmd, UblkIoDesc},
    zram::{ZramDevice, ZramConfig},

    // Virtualization
    vmm::{Vmm, VmConfig, Jailer},

    // SIMD compute
    simd::{SimdOps, SimdCapabilities},

    // GPU compute
    gpu::{GpuContext, GpuExecutor, ComputeShader},

    // Distributed computing
    pool::Pool,
    task::Task,
    scheduler::Scheduler,

    // Serverless
    serverless::{Function, Trigger, FunctionService},
};

#[tokio::main]
async fn main() -> Result<()> {
    // Create execution pool with all backends
    let pool = Pool::builder()
        .cpu_workers(8)
        .gpu_device(0)
        .microvm_pool(16)
        .simd_enabled(true)
        .zram_backing(ZramConfig::default())
        .build()
        .await?;

    // Submit CPU task with SIMD
    let simd_task = Task::simd(|ctx| {
        let a = ctx.load_tensor("a")?;
        let b = ctx.load_tensor("b")?;
        ctx.store_tensor("c", ctx.matmul(&a, &b))
    }).build();
    pool.submit(simd_task).await?;

    // Submit GPU task
    let gpu_task = Task::shader(include_str!("shader.wgsl"))
        .workgroups(64, 64, 1)
        .build();
    pool.submit(gpu_task).await?;

    // Submit isolated task (microVM)
    let vm_task = Task::binary("./untrusted")
        .backend(Backend::MicroVm)
        .memory_mib(256)
        .build();
    pool.submit(vm_task).await?;

    Ok(())
}
```

## 9. Implementation Roadmap

### Phase 1: Kernel Interfaces (DONE)
- [x] io_uring structures
- [x] ublk structures
- [x] blk_mq structures
- [x] memory management
- [x] error types

### Phase 2: Distributed Computing (DONE)
- [x] Work-stealing scheduler
- [x] Task types
- [x] CPU executor
- [x] Message transport
- [x] Fault tolerance
- [x] Pool API

### Phase 3: zram & SIMD (DONE)
- [x] zram device implementation
- [x] LZ4 compression (pure Rust)
- [x] SIMD detection
- [x] AVX-512/AVX2/SSE vectorized ops
- [x] NEON/SVE for aarch64
- [ ] trueno integration (optional - uses trueno crate)

### Phase 4: GPU Compute (DONE)
- [x] wgpu-style API (mock implementation)
- [x] Shader compilation (WGSL support)
- [x] Buffer management
- [ ] rust-gpu support (optional)

### Phase 5: Virtualization (DONE)
- [x] KVM interface (mock, constants ready)
- [x] vCPU management
- [x] Guest memory
- [x] virtio-blk (basic)
- [x] virtio-vsock (basic)
- [x] Jailer security

### Phase 6: Serverless (DONE)
- [x] Function model
- [x] Event triggers
- [x] Cold start optimization
- [x] Warm pool

### Phase 7: Integration (COMPLETE)
- [x] MicroVM executor in repartir
- [x] SIMD executor in repartir
- [x] virtio devices (vsock, block) in pepita
- [x] Full pepita-repartir integration tests (32 integration tests)

---

**Document Status:** COMPLETE - v2.0.0 (Pepita Unified Architecture)
**Last Updated:** 2026-01-04
