content: blog: Add v53.0 release

Signed-off-by: Rob Bradford <rbradford@meta.com>

Author: rbradford

content/en/blog/v53.0/index.md

@@ -0,0 +1,200 @@
+---
+title: "Cloud Hypervisor v53.0 Released!"
+date: 2026-07-12T21:55:39Z
+draft: false
+contributors: [Cloud Hypervisor Team]
+---
+This release has been tracked in [v53.0 group](https://github.com/orgs/cloud-hypervisor/projects/6/views/6?filterQuery=release%3A%22Release+53%22) of our [roadmap project](https://github.com/orgs/cloud-hypervisor/projects/6/).
+
+### Snapshot/Restore and Live Migration Improvements
+
+* An offloaded snapshot/restore daemon has been introduced, allowing snapshot
+  and restore to be carried out by an external process. The live migration
+  protocol has been extended so page faults can be serviced from the source.
+  This enables *postcopy* for remote live migration and *on-demand paging* for
+  the offload daemon, both built on `userfaultfd`, bringing the offload daemon
+  to parity with the internal snapshot/restore implementation (#8403, #8264,
+  #8556).
+* Snapshot pages can now be prefaulted in the background after a
+  `userfaultfd`-based restore, combining a fast restore-to-resume with fully
+  faulted-in memory shortly afterwards. The number of prefault threads scales
+  with the available parallelism (#8150, #8538, #8484).
+* Live migration data can now be encrypted using mutual TLS (#8053).
+* VFIO migration v2 is now supported for same-host snapshot and restore of
+  migratable VFIO devices (for example ConnectX VFs bound to `mlx5_vfio_pci`)
+  (#8303).
+* Migrated guests now issue post-migration network announcements so that
+  connectivity on the new host is refreshed within milliseconds rather than
+  taking up to 20 seconds to recover (#8263).
+* The `vm.send-migration` API endpoint now returns immediately rather than
+  blocking for the duration of the migration (#8021).
+
+### Nested Hyper-V (Windows Guest) Support
+
+Windows guests can now run nested Hyper-V as used by WSL2 on the KVM backend
+(#8481).
+
+### `virtio-rtc` Device Support
+
+Support for `virtio-rtc` devices has been added (via `--rtc`), providing a
+Real Time Clock to the guest. This is primarily useful for, and only enabled by
+default on, MSHV guests that do not have access to `kvmclock` (#7795).
+
+### Guest Clock Updates Across Snapshot/Restore and Migration
+
+The guest clock is now advanced to account for the elapsed wall-clock time when
+a VM is resumed after a snapshot-restore or a live migration so the guest sees
+the correct time of day immediately rather than lagging behind by the downtime.
+On x86 the kvmclock realtime flag is preserved so that the kernel adjusts the
+clock automatically (#8256). On ARM64 the guest counter is advanced using the
+`KVM_REG_ARM_TIMER_CNT` interface (#8343). vCPU TSC offsets are also
+re-synchronized on restore (#8437).
+
+### Buffered Serial Output for Late-Connecting Clients
+
+In socket serial mode (`--serial socket=...`) the output produced before a
+client connects is now buffered so a console client that attaches after boot
+sees the earlier output (#8322).
+
+### New Command-Line and API Options
+
+* A `reserve=on|off` option has been added to `--memory` and
+  `--memory-zone` (default `off`). When enabled, guest RAM is mapped
+  without `MAP_NORESERVE` so an overcommitted configuration fails cleanly at VM
+  creation with `ENOMEM` (#8350).
+* The SMBIOS/DMI fields exposed via `--platform` have been extended and scoped
+  to specific SMBIOS structures, for workloads that consume this data for
+  licensing, inventory, or host identification (#8259).
+* The VMM can now consume pre-opened VFIO `cdev` and `iommufd` file descriptors
+  supplied by the caller, letting a privileged orchestrator open the device
+  nodes once and hand the FDs to an unprivileged VMM at boot or at runtime.
+  This is also a prerequisite for live migration of VMs using VFIO devices
+  (#8287).
+* A "glog style" log format has been added, with a single-character level and
+  local or UTC timestamps (#8265).
+* A new `--seccomp=errno` option has been added that will result in filtered
+  syscalls to set `errno` to `EPERM`. This can be used when the killing of the
+  process with `SIGSYS` is not desired (#8578).
+
+### Deprecations
+
+* The legacy `--platform` SMBIOS keys `serial_number` and `uuid` are
+  deprecated in favor of the new SMBIOS-structure-scoped keys. The
+  legacy keys continue to be accepted, with a warning, and will be
+  removed in a future release (#8259).
+* The generic `vhost-user` device's `virtio_id` command-line
+  parameter is deprecated in favor of `device_type`, matching the API
+  and configuration naming. `virtio_id` is retained as an alias that
+  logs a warning and will be removed in a later release (#8564).
+
+### Notable Bug Fixes
+
+* Revert `create memfd for private mappings`, which caused a serious memory
+  consumption regression without hugepages or `shared=on` (#8246).
+* Advertise the mandatory Hyper-V partition privileges so Windows
+  guests enable the reference TSC page instead of taking a VM exit on
+  every clock read (#8380).
+* Correctly save and restore ARM64 SVE registers (#8268).
+* Set the guest physical address space size correctly on AMD (#8291).
+* Sparse align the initial PCI BAR placement to avoid a Windows rebalancing
+  deadlock (#8205).
+* Various TPM fixes, including for Windows guests (#8305, #8312).
+* Preserve `WRITE_ZEROES` on QCOW2 images with backing files (#8245)
+  and fix `WriteZeroes` sector arithmetic overflow (#8388).
+* Improve `O_DIRECT` handling so that `direct=on` is usable on hosts
+  requiring 4K alignment, including opening fixed VHD images (#8335).
+* Resolve relative QCOW2 backing file paths correctly (#8196).
+* Drain block I/O before the device is paused (#8356) and retry
+  locking when interrupted by `EINTR` (#8402).
+* Fix VHDX region-table overlap detection (#8483) and an incomplete
+  bounds check in the VHDX synchronous I/O worker (#8529).
+* Fix a guest deadlock by signalling `DEVICE_NEEDS_RESET` and
+  releasing the activation barrier when a virtio device fails to
+  activate (#8295).
+* Handle short and misaligned MMIO/PIO accesses without panicking:
+  validate the MMIO access size (#8506), return all-ones for
+  unregistered MMIO/PIO reads (#8237), correct `fw_cfg` short and long
+  reads (#8507), respect the PCI CFG capability length for BAR access
+  (#8272, #8238), and reject incorrect MSI-X table and PBA reads (#8417).
+* Translate virtio-iommu buffers that span adjacent mappings (#8520),
+  and add centralized virtio descriptor-range validation (#8232).
+* Handle a guest/host half-close on vsock connections (#8372).
+* Avoid a guest-triggerable VMM panic by replacing asserts on ACPI
+  device accesses with checks (#8405).
+* Emit a complete ACPI `_S5_` sleep package, fixing an early-boot
+  fault on OpenBSD guests (#8426).
+* Transfer post-snapshot guest memory changes during live migration to
+  avoid corruption with `vhost-user` devices (#8361).
+* Improve configuration validation to return errors instead of
+  panicking on malformed input (#8511), require the `ch-remote`
+  snapshot/restore config arguments instead of panicking (#8331),
+  reject resizing below the boot memory size (#8428), reject removal of
+  an already-removed device (#8559), and fix generic `vhost-user`
+  parsing (#8564).
+* Don't leak a file descriptor when ejecting a VFIO device (#8367),
+  and fix a PCI device hotplug race by deferring device visibility
+  (#8369).
+* Fix PCI segment ID validation (#8377) and make the PCI BDF
+  configurable for the balloon and ivshmem devices (#8310).
+* Return HTTP 404 for API requests against a VM that has not been
+  created (#8320), and omit unset optional fields from API responses so
+  that strict client generators accept them (#8321).
+* Clean up a stale API socket under a lock before binding (#8325).
+* Cache the local timezone before installing seccomp filters (#8327).
+* Enhance the ACPI PPTT with cache topology information (#7893).
+* Correct several OpenAPI specification entries: the
+  `iommu_address_width` field name (#8244), integer schema formats
+  (#8278), `GenericVhostUserConfig` properties (#8543), a parameter
+  name (#8544), and the `vmm.nmi` to `vm.nmi` endpoint (#8571).
+* Deduplicate `VmConfig::preserved_fds` (#8271).
+
+### Contributors
+
+Many thanks to everyone who has contributed to our release:
+
+* Aastha Rawat <aastharawat@microsoft.com>
+* Adel-Ayoub <adelayoub.maaziz@gmail.com>
+* Alexander Lvov <alexander.lvov.git@gmail.com>
+* Alyssa Ross <hi@alyssa.is>
+* Anatol Belski <anbelski@linux.microsoft.com>
+* Andrei Vagin <avagin@google.com>
+* Anirudh Rayabharam <anrayabh@microsoft.com>
+* Atish Patra <atishp@meta.com>
+* Bo Chen <bchen@crusoe.ai>
+* Cameron Baird <cameronbaird@microsoft.com>
+* Chris Webb <chris@arachsys.com>
+* CMGS <ilskdw@gmail.com>
+* Damian Barabonkov <dbctl@pm.me>
+* Daniel Verkamp <drv@meta.com>
+* doge <me@crackerben.com>
+* Dylan Reid <dgreid@fb.com>
+* Gauthier Jolly <contact@gjolly.fr>
+* Henry Hrvoje Tonkovac <htonkovac@gmail.com>
+* Ian Klemm <hi@ianklemm.de>
+* Julian Schindel <julian.schindel@cyberus-technology.de>
+* Leander Kohler <leander.kohler@cyberus-technology.de>
+* Max Makarov <maxpain@linux.com>
+* Meng Zhuo <mengzhuo@iscas.ac.cn>
+* Muminul Islam <muislam@microsoft.com>
+* Nikolas Kyx <55556836+nyx191@users.noreply.github.com>
+* Oliver Anderson <oliver.anderson@cyberus-technology.de>
+* Pascal Scholz <pascal.scholz@cyberus-technology.de>
+* Philipp Schuster <philipp.schuster@cyberus-technology.de>
+* Rob Bradford <rbradford@meta.com>
+* Roman <roman@vanesyan.com>
+* Rowen-Ye <rowenye1@gmail.com>
+* Ruben Hakobyan <hruben@meta.com>
+* Saravanan D <saravanand@crusoe.ai>
+* Sayed Kaif <metsw24@gmail.com>
+* Sebastian Eydam <sebastian.eydam@cyberus-technology.de>
+* Sebastien Boeuf <sboeuf@meta.com>
+* tchaton <thomas.chaton.ai@gmail.com>
+* Thomas Prescher <thomas.prescher@cyberus-technology.de>
+* tonic <tonicbupt@gmail.com>
+* Tushar Khatri <hello@tusharkhatri.in>
+* wangyf0611 <wangyufeng@iscas.ac.cn>
+* Wei Liu <liuwe@microsoft.com>
+* wuxinyue <wuxinyue.wxy@antgroup.com>
+* yanjianqing <yanjianqing@kylinos.cn>
+### Download
+ See the <a href="https://github.com/cloud-hypervisor/cloud-hypervisor/releases/tag/v53.0">GitHub Release</a> for the release assets.