content: blog: Release v51.0

Signed-off-by: Bo Chen <bchen@crusoe.ai>

Author: likebreath

content/en/blog/v51.0/index.md

@@ -0,0 +1,135 @@
+---
+title: "Cloud Hypervisor v51.0 Released!"
+date: 2026-02-20T01:34:50Z
+draft: false
+contributors: [Cloud Hypervisor Team]
+---
+This release has been tracked in [v51.0 group](https://github.com/orgs/cloud-hypervisor/projects/6/views/6?filterQuery=release%3A%22Release+51%22) of our [roadmap project](https://github.com/orgs/cloud-hypervisor/projects/6/).
+
+Security Fixes
+--------------
+
+This release fixes a security vulnerability in disk image handling.
+Details can be found in [GHSA-jmr4-g2hv-mjj6](https://github.com/cloud-hypervisor/cloud-hypervisor/security/advisories/GHSA-jmr4-g2hv-mjj6).
+
+* A new `backing_files=on|off` option has been added to `--disk` to
+  explicitly control whether QCOW2 backing files are permitted. This
+  defaults to `off` to prevent the loading of backing files entirely.
+  (#7685)
+* Explicit image type specification via the user interface, removing
+  reliance on format autodetection (#7728).
+* Prevent sector-zero writes for autodetected raw images (#7728).
+
+Significant QCOW2 v3 Improvements
+---------------------------------
+
+A large number of QCOW2 v3 specification features have been implemented:
+
+* RAW backing file support for QCOW2 overlays (#7570)
+* Zero bit in L2 entries (#7627)
+* Incompatible feature bit validation (#7612)
+* Dirty bit support (#7636)
+* Variable refcount widths (1 to 64-bit) (#7633)
+* Corrupt bit detection and marking (#7639)
+* Autoclear feature bits handling (#7648)
+* Thread safety fix for multiple virtio queues (`num_queues > 1`)
+  (#7661)
+* Correct zero-fill for reads beyond backing file size (#7678)
+* Live disk resize support (#7687)
+
+ACPI Generic Initiator Support
+------------------------------
+
+ACPI Generic Initiator Affinity (SRAT Type 5) support has been added
+to associate VFIO-PCI devices with dedicated memory/CPU-less NUMA
+nodes. This enables the guest OS to make NUMA-aware memory allocation
+decisions for device workloads. A new `device_id` parameter has been
+added to `--numa` for specifying VFIO devices. (#7626)
+
+Block Device DISCARD and WRITE_ZEROES Support
+---------------------------------------------
+
+The `virtio-blk` device now supports `DISCARD` and `WRITE_ZEROES`
+operations for QCOW2 and RAW image formats. This enables thin
+provisioning and efficient space reclamation when guests trim
+filesystems. A new `sparse=on|off` option has been added to `--disk` to
+control disk space management: `sparse=on` (default) enables thin
+provisioning with space reclamation, while `sparse=off` provides thick
+provisioning with consistent I/O latency. (#7666)
+
+Notable Performance Improvements
+--------------------------------
+
+* Transparent Huge Pages (THP) support has been extended to cover
+  anonymous shared memory (`shared=on`) via `madvise`. Previously, THP
+  was only used for non-shared memory. (#7646)
+* The `vhost-user-net` device now uses the default set of vhost-user
+  virtio features, including `VIRTIO_F_RING_INDIRECT_DESC`, which
+  provides a performance improvement. (#7653)
+
+MSHV Support Improvements
+-------------------------
+
+* Optimize CPU state update after emulation by only updating special
+  registers when changed (#7603)
+* Enable SMT for guests with `threads_per_core > 1` (#7668)
+* Stub `save_data_tables()` to unblock VM pause/resume (#7692)
+* Handle `GHCB_INFO_SPECIAL_DBGPRINT` VMG exit in SEV-SNP guest exit
+  handler (#7703)
+* Fix CVM boot failure on MSHV (#7548)
+* Fix CPU topology detection for multithreaded configurations (#7576)
+
+Notable Bug Fixes
+-----------------
+
+* Fix VFIO device hot-remove leaving group and container file
+  descriptors open, preventing re-add (#7676)
+* Fix snapshot restore when backing file is on read-only storage with
+  `shared=false` (#7674)
+* Enforce `VIRTIO_BLK_F_RO` even if guest does not negotiate it
+  (#7705)
+* Fix read-only block device FLUSH requests from OVMF preventing VMs
+  from booting (#7706)
+* Fix vhost-user device not properly dropping unowned file descriptors
+  (#7679)
+* Fix `vhost-user-block` `get_config` interoperability (#7617)
+* Fix vsock TOCTOU race condition by copying packet header from guest
+  memory before processing (#7530)
+* Fix vsock handling of large TX packets spanning multiple data
+  descriptors (#7680)
+* Add `gettid()` to all seccomp filters (#7596)
+* Fix MAC address parsing that wrongly allowed `+` instead of hex
+  characters (#7579)
+* Improve UUID parse error message and `--net` fd help text (#7702)
+* Fix various inconsistencies in our OpenAPI specification file
+  (#7716, #7726)
+* Various documentation fixes (#7602, #7606)
+
+Contributors
+------------
+
+Many thanks to everyone who has contributed to our release:
+
+* Aastha Rawat <aastharawat@microsoft.com>
+* Alyssa Ross <hi@alyssa.is>
+* Anatol Belski <anbelski@linux.microsoft.com>
+* Anirudh Rayabharam <anrayabh@microsoft.com>
+* Bo Chen <bchen@crusoe.ai>
+* Champ-Goblem <cameron@northflank.com>
+* Changyuan Lyu <changyuanl@google.com>
+* Damian Barabonkov <dbctl@pm.me>
+* Demi Marie Obenour <demiobenour@gmail.com>
+* Leander Kohler <leander.kohler@cyberus-technology.de>
+* Muminul Islam <muislam@microsoft.com>
+* Philipp Schuster <philipp.schuster@cyberus-technology.de>
+* Rob Bradford <rbradford@meta.com>
+* Rowen-Ye <rowenye1@gmail.com>
+* Saravanan D <saravanand@crusoe.ai>
+* Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
+* Thomas Leroy <thomas.leroy.mp@gmail.com>
+* Wei Liu <liuwe@microsoft.com>
+* Yi Wang <foxywang@tencent.com>
+* Zhibin Li <banlu.lzb@antgroup.com>
+* stevenhorsman <steven@uk.ibm.com>
+### Download
+ See the <a href="https://github.com/cloud-hypervisor/cloud-hypervisor/releases/tag/v51.0">GitHub Release</a> for the release assets.