feat(krun): expand DiskBuilder with id, cache, direct_io, sync#51
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feat(krun): expand DiskBuilder with id, cache, direct_io, sync#51
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Surface the per-disk knobs that libkrun's krun_add_disk3 C API already
supports but the Rust wrapper had hardcoded. This lets callers attach
extra disks as volumes (not just a rootfs) with stable identifiers and
per-disk safety/perf settings.
- Add CacheMode { Writeback, Unsafe } and SyncMode { None, Relaxed, Full }
enums with From impls to devices::virtio::{CacheType, block::SyncMode}.
- Add DiskBuilder::id() for caller-chosen block_ids, enabling guest
addressing via /dev/disk/by-id/virtio-<id> independent of attach order.
- Add DiskBuilder::cache(), direct_io(), sync() alongside the existing
path/format/read_only methods.
- Replace the naive format!("vd{}", (b'a' + i) as char) device-id
fallback, which rolled over into invalid characters past vdz, with a
bijective base-26 vd_suffix() helper matching block/genhd.c's
disk_name() scheme (vda..vdz, vdaa..vdzz, vdaaa...).
- Re-export CacheMode and SyncMode from the crate root.
Defaults (Writeback cache, direct_io=false, Full sync) preserve the
previous hardcoded behavior, so existing .disk(|d| d.path().format()
.read_only()) callers are unaffected.
When the caller passes a non-empty id via DiskBuilder::id() it now shows up in the guest as the virtio-blk serial (visible at /sys/block/<dev>/serial and, with udev, /dev/disk/by-id/virtio-<id>). Previously the id was stored as Block.id but disk_image_id was always generated from the host file's st_rdev + st_ino, so the configured id never reached the guest. Falls back to the rdev+inode default when id is empty, preserving existing behaviour for callers that do not set an id. Padding/truncation matches the existing default path: zero-padded to VIRTIO_BLK_ID_BYTES (20), with longer ids truncated.
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appcypher
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Apr 26, 2026
Bump all msb_krun_* workspace crates and their internal path-dependency version refs from 0.1.10 to 0.1.11, and refresh both lockfiles. The libkrun C-API crate (1.17.3) and the rust_vm example are unchanged. Changes since 0.1.10: - feat(krun): expand DiskBuilder with id, cache, direct_io, sync (#51) - msb_krun_cpuid: fix compilation on Rust 1.93 by wrapping CPUID calls in unsafe blocks (#50)
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Summary
DiskBuilderwithid(),cache(),direct_io(), andsync()methods, surfacing per-disk knobs that libkrun'skrun_add_disk3C API already supports but the Rust wrapper had hardcoded.CacheMode { Writeback, Unsafe }andSyncMode { None, Relaxed, Full }enums (re-exported at the crate root) withFromimpls intodevices::virtio::{CacheType, block::SyncMode}.format!("vd{}", (b'a' + i) as char)rolled over into invalid characters (vd{,vd|, ...) past the 26th disk. Replaced with avd_suffix()helper implementing the kernel's bijective base-26disk_name()scheme (vda..vdz,vdaa..vdzz,vdaaa...)./dev/disk/by-id/virtio-<id>independent of attach order.Writebackcache,direct_io=false,Fullsync) preserve the previous hardcoded behavior, so existing.disk(|d| d.path().format().read_only())callers are unaffected.Test Plan
cargo build -p msb_krun(no features) passescargo build -p msb_krun --features blkpassescargo build -p msb_krun --features blk,netpassescargo test -p msb_krun --features blkpasses — 7 unit + 22 doctests (includes four new tests:vd_suffix_matches_kernel_scheme,disk_builder_preserves_insertion_order,disk_builder_auto_id_then_custom,disk_builder_per_disk_settings_dont_leak)cargo clippy -p msb_krun --features blk -- -D warningsclean