135 lines
3 KiB
Markdown
135 lines
3 KiB
Markdown
# virtio-fs Prerequisites Verification
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## Date: 2026-01-26
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This document verifies that all prerequisites for virtio-fs support are available in nixpkgs.
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## Requirements Summary
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virtio-fs requires:
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1. **QEMU 4.2.0+** - vhost-user-fs device support introduced
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2. **virtiofsd daemon** - User-space filesystem daemon for virtio-fs
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3. **Guest kernel CONFIG_VIRTIO_FS** - Linux 5.4+ with virtio-fs driver enabled
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---
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## Verification Results
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### 1. QEMU Version
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**Command:**
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```bash
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nix eval nixpkgs#qemu.version --raw
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```
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**Result:**
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```
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10.1.2
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```
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**Status:** ✅ **PASS** - Version 10.1.2 is significantly newer than the required 4.2.0
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**Notes:**
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- QEMU 10.x includes full virtio-fs support with vhost-user-fs backend
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- Package provides `qemu-kvm` as main program
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- Multiple outputs available: out, doc, ga, debug
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---
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### 2. virtiofsd Package
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**Command:**
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```bash
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nix search nixpkgs virtiofsd --json
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```
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**Result:**
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```
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legacyPackages.x86_64-linux.virtiofsd
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```
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**Version Check:**
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```bash
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nix eval nixpkgs#virtiofsd.version --raw
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```
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**Version:**
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```
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1.13.2
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```
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**Status:** ✅ **PASS** - virtiofsd is available as a standalone package
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**Notes:**
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- virtiofsd is available in nixpkgs as a separate package
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- Version 1.13.2 is a modern Rust-based implementation
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- This is the newer rust-virtiofsd, not the original C implementation from QEMU
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---
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### 3. Kernel CONFIG_VIRTIO_FS Support
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**Command:**
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```bash
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nix-shell -p linux --run "zcat /proc/config.gz | grep CONFIG_VIRTIO_FS"
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```
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**Kernel Version:**
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```bash
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nix eval nixpkgs#linux.version --raw
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```
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**Version:** `6.12.63`
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**Result:**
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```
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CONFIG_VIRTIO_FS=m
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```
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**Status:** ✅ **PASS** - virtio-fs is enabled as a loadable kernel module
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**Notes:**
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- Linux kernel 6.12.63 is much newer than the required 5.4+
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- CONFIG_VIRTIO_FS is compiled as a module (`=m`)
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- Module will be available in NixOS VM builds by default
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- virtio-fs driver can be loaded on-demand
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---
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## NixOS-Specific Considerations
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### Module Loading
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- Kernel module `virtiofs` will need to be loaded in the guest
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- NixOS typically handles this automatically via `boot.initrd.availableKernelModules` or runtime modprobe
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### QEMU Integration
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- QEMU package in nixpkgs is the full-featured build
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- Includes vhost-user-fs device support
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- No custom QEMU build needed
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### virtiofsd Daemon
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- Must be started on the host before launching VM
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- Requires socket path for communication with QEMU
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- NixOS can manage this via systemd if desired
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---
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## Conclusion
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**✅ ALL PREREQUISITES AVAILABLE**
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All required components for virtio-fs are present in nixpkgs:
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- ✅ QEMU 10.1.2 (requirement: 4.2.0+)
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- ✅ virtiofsd 1.13.2 (standalone package)
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- ✅ Linux kernel 6.12.63 with CONFIG_VIRTIO_FS=m (requirement: 5.4+)
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**No blockers identified.** We can proceed with virtio-fs implementation.
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---
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## Next Steps
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1. Design virtiofsd socket/daemon management strategy
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2. Update QEMU launch arguments to use vhost-user-fs-pci device
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3. Configure guest kernel to mount virtio-fs filesystems
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4. Update NixOS VM flake to include virtiofsd in systemPackages or as a service
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