Implement M6B virtio block transport

CHANGELOG.md

@@ -1,5 +1,21 @@
 # Changelog
 
+## M6B Virtio Block Transport candidate — 2026-07-26
+
+- Architecture-independent 512-byte sector block-device contract.
+- Validated I/O, 32-bit, and 64-bit PCI BAR decoding.
+- Modern virtio PCI common, notify, device, and configuration-window parsing.
+- `VIRTIO_F_VERSION_1` negotiation and fail-closed device initialization.
+- Allocator-owned, direct-mapped split virtqueue with one outstanding request.
+- Polling read, write, and device-ID requests with status/reset/timeout errors.
+- Dedicated disk identity verification and known-sector read evidence.
+- Disposable-sector write/readback followed by restoration of original bytes.
+- Sector-boundary rejection and `block` shell diagnostics.
+- Capability registry version 5 and full M5/FH1/FH2/FH3/M6A regressions.
+
+M6B does not mount a filesystem or expose general-purpose persistent writes.
+Buffer caching and VFS contracts remain M6C; read-only FAT32 remains M6D.
+
 ## M6A PCI and Storage Discovery candidate — 2026-07-26
 
 - Architecture-independent PCI identity and storage classification.

PROJECT.md

@@ -6,9 +6,9 @@
 - Architecture: x86-64
 - Firmware: UEFI 2.x
 - Primary language: Rust 2024
-- Accepted checkpoint: Foundation Hardening Phase 3
-- Immutable release: `v0.0.8-fh3`
-- Current development checkpoint: M6A PCI and storage discovery
+- Accepted checkpoint: M6A PCI and Storage Discovery
+- Immutable release: `v0.0.9-m6a`
+- Current development checkpoint: M6B virtio block transport
 - Deployment policy: QEMU only until physical-install safety gates pass
 
 ## Mission
@@ -21,11 +21,12 @@ Development is grouped into major milestone batches. Small formatting or CI corr
 
 ## Current objective
 
-Enumerate the QEMU PCI topology through hardware configuration transactions,
-retain a bounded device inventory, and match a dedicated virtio block target
-without issuing disk I/O.
+Activate the dedicated QEMU virtio block target behind an
+architecture-independent sector contract. Validate modern PCI capabilities,
+feature negotiation, DMA queue ownership, a known-sector read, and a confined
+write/readback/restore transaction.
 
 ## Next major objective
 
-Add a polling virtio-blk transport and architecture-independent block-device
-API after M6A passes QEMU.
+Add a fixed-capacity block cache and VFS contracts without enabling persistent
+filesystem writes.

README.md

@@ -6,15 +6,15 @@ SanjuOS is an independent, Rust-first desktop operating-system project. It is
 not a Linux distribution. Development proceeds through emulator-verified kernel
 milestones before any physical-disk work.
 
-## Current checkpoint: M6A PCI and Storage Discovery
+## Current checkpoint: M6B Virtio Block Transport
 
 The accepted baseline entering this phase was the Foundation Hardening Phase 2
 candidate. M0 through FH2 proved UEFI ownership transfer, protected kernel
 execution, interrupts, Ring 3 entry, `SYSCALL`/`SYSRET`, ELF64 loading,
 recoverable user faults, physical ownership, and a fresh SanjuOS page-table
 root.
 
-The accepted `v0.0.8-fh3` release turns the process runtime into an active
+The accepted `v0.0.8-fh3` release turned the process runtime into an active
 hardware boundary:
 
 - each M5 process owns a deep-cloned four-level page-table root;
@@ -31,19 +31,30 @@ hardware boundary:
 The authoritative maturity status is generated at
 [`docs/CAPABILITY_MATRIX.md`](docs/CAPABILITY_MATRIX.md).
 
-M6A now begins the storage stack without issuing disk I/O:
+The accepted `v0.0.9-m6a` release begins the storage stack without issuing
+disk I/O:
 
 - x86 PCI configuration mechanism #1 is probed directly;
 - bus/device/function discovery handles multifunction devices and bridges;
 - an allocation-free kernel inventory classifies storage controllers;
 - QEMU attaches a disposable second disk through `virtio-blk-pci`;
 - boot and shell evidence must identify that exact block target;
-- sector I/O remains the separate M6B acceptance gate.
+- sector I/O remains a separate acceptance gate.
+
+M6B implements that gate on the dedicated QEMU test disk:
+
+- an architecture-independent, sector-based block-device contract;
+- validated PCI BARs and modern virtio PCI capabilities;
+- `VIRTIO_F_VERSION_1` negotiation with unsupported read-only media rejected;
+- one allocator-owned, direct-mapped DMA page containing a split virtqueue;
+- bounded polling with reset, status, and timeout failures returned safely;
+- a seeded read test plus a disposable write/readback/restore transaction;
+- a `block` shell diagnostic and exact QEMU acceptance evidence.
 
 ## Shell commands
 
 ```text
-help version userspace uptime memory irq tasks ls cat write echo clear
+help version userspace uptime memory irq tasks pci block ls cat write echo clear
 ```
 
 ## Build and verify
@@ -73,11 +84,12 @@ docs/               Requirements, architecture, ADRs, testing, security, process
 
 ## Current boundary
 
-M6A and FH3 remain single-core and PIT-driven. The combined EFI-stub kernel still
+M6B and FH3 remain single-core and PIT-driven. Block completion is synchronous
+and polling, one request is outstanding at a time, and only the explicitly
+identified disposable QEMU disk is used. The combined EFI-stub kernel still
 retains a bounded identity mapping while a separate high-half kernel image is
-designed. Per-process floating-point/SIMD state, SMP, local APIC timers, PCID,
-copy-on-write, and demand paging remain future hardening work. PCI discovery,
-the virtio block transport, a persistent VFS, and graphics are later gates.
+designed. A block cache, VFS, read-only FAT32, persistent writes, physical-disk
+installation, graphics, SMP, and local APIC timers remain later gates.
 
 ## Safety
 

SOURCE_MANIFEST.sha256

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 fa978f37685c47c2209dc2c11e4bb7d278ab47a813b051d1b25ad66e3eafc770  CONTRIBUTING.md
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boot/uefi/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sanju-boot"
-version = "0.0.9"
+version = "0.0.10"
 edition.workspace = true
 rust-version.workspace = true
 publish.workspace = true

boot/uefi/src/arch/x86_64/mod.rs

@@ -3,6 +3,7 @@
 pub(crate) mod paging;
 mod pci;
 mod serial;
+mod virtio_block;
 
 #[cfg(feature = "qemu-test")]
 pub mod qemu;
@@ -14,6 +15,7 @@ pub(crate) use paging::{
 };
 pub(crate) use pci::discover_pci;
 pub use serial::SerialConsole;
+pub(crate) use virtio_block::initialize_and_probe as initialize_virtio_block;
 
 use core::arch::{asm, global_asm};
 use core::mem::size_of;