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CHANGELOG.md

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Changelog

Notable changes to Xen will be documented in this file.

The format is based on Keep a Changelog

4.20.0 UNRELEASED - TBD

Changed

  • Fixed blkif protocol specification for sector sizes different than 512b.
  • On x86:
    • Prefer ACPI reboot over UEFI ResetSystem() run time service call.
    • Switched the xAPIC flat driver to use physical destination mode for external interrupts instead of logical destination mode.

Added

  • On Arm:
    • Experimental support for Armv8-R.

Removed

  • On x86:
    • Support for running on Xeon Phi processors.
    • Removed the ucode=allow-same command line option.
    • Removed x2APIC Cluster Mode for external interrupts. x2APIC Physical and Mixed Modes are still available.

4.19.0 - 2024-07-29

Changed

  • Changed flexible array definitions in public I/O interface headers to not use "1" as the number of array elements.
  • The minimum supported OCaml toolchain version is now 4.05
  • On x86:
    • HVM PIRQs are disabled by default.
    • Reduce IOMMU setup time for hardware domain.
    • Allow HVM/PVH domains to map foreign pages.
    • Declare PVH dom0 supported with caveats.
  • xl/libxl configures vkb=[] for HVM domains with priority over vkb_device.
  • Increase the maximum number of CPUs Xen can be built for from 4095 to 16383.
  • When building with Systemd support (./configure --enable-systemd), remove libsystemd as a build dependency. Systemd Notify support is retained, now using a standalone library implementation.
  • xenalyze no longer requires --svm-mode when analyzing traces generated on AMD CPUs
  • Code symbol annotations and MISRA compliance improvements.
  • CI updates:
    • Minimum fixes to rebuild the containers, following the HEREDOC problems.
    • Rebuild containers to have testing with up-to-date LTS distros.
    • Few build system checks, and strip the obsolete contents of the build containers.

Added

  • On x86:
    • Introduce a new x2APIC driver that uses Cluster Logical addressing mode for IPIs and Physical addressing mode for external interrupts.
  • On Arm:
    • FF-A notification support.
    • Introduction of dynamic node programming using overlay dtbo.
  • Add a new 9pfs backend running as a daemon in dom0. First user is Xenstore-stubdom now being able to support full Xenstore trace capability.
  • libxl support for backendtype=tap with tapback.

Removed

  • caml-stubdom. It hasn't built since 2014, was pinned to Ocaml 4.02, and has been superseded by the MirageOS/SOLO5 projects.
  • /usr/bin/pygrub symlink. This was deprecated in Xen 4.2 (2012) but left for compatibility reasons. VMs configured with bootloader="/usr/bin/pygrub" should be updated to just bootloader="pygrub".
  • The Xen gdbstub on x86.
  • xentrace_format has been removed; use xenalyze instead.

4.18.0 - 2023-11-16

Changed

  • Repurpose command line gnttab_max_{maptrack_,}frames options so they don't cap toolstack provided values.
  • Ignore VCPUOP_set_singleshot_timer's VCPU_SSHOTTMR_future flag. The only known user doesn't use it properly, leading to in-guest breakage.
  • The "dom0" option is now supported on Arm and "sve=" sub-option can be used to enable dom0 guest to use SVE/SVE2 instructions.
  • Physical CPU Hotplug downgraded to Experimental and renamed "ACPI CPU Hotplug" for clarity

Added

  • On x86:
    • On all Intel systems, MSR_ARCH_CAPS is now visible in guests, and controllable from the VM's config file. For CPUs from ~2019 onwards, this allows guest kernels to see details about hardware fixes for speculative mitigations. (Backported as XSA-435 to older releases).
    • xl/libxl can customize SMBIOS strings for HVM guests.
    • Support for enforcing system-wide operation in Data Operand Independent Timing Mode.
    • Add Intel Hardware P-States (HWP) cpufreq driver.
    • Support for features new in AMD Genoa CPUs:
      • CPUID_USER_DIS (CPUID Faulting) used by Xen to control PV guest's view of CPUID data.
    • Support for features new in Intel Sapphire Rapids CPUs:
      • PKS (Protection Key Supervisor) available to HVM/PVH guests.
      • VM-Notify used by Xen to mitigate certain micro-architectural pipeline livelocks, instead of crashing the entire server.
      • Bus-lock detection, used by Xen to mitigate (by rate-limiting) the system wide impact of a guest misusing atomic instructions.
    • Support for features new in Intel Granite Rapids CPUs:
      • AVX512-FP16.
  • On Arm:
    • Xen supports guests running SVE/SVE2 instructions. (Tech Preview)
    • Add suport for Firmware Framework for Arm A-profile (FF-A) Mediator (Tech Preview)
    • Experimental support for dynamic addition/removal of Xen device tree nodes using a device tree overlay binary (.dtbo).
  • Introduce two new hypercalls to map the vCPU runstate and time areas by physical rather than linear/virtual addresses.
  • The project has now officially adopted 6 directives and 65 rules of MISRA-C.

Removed

  • On x86, the "pku" command line option has been removed. It has never behaved precisely as described, and was redundant with the unsupported "cpuid=no-pku". Visibility of PKU to guests should be via its vm.cfg file.
  • xenpvnetboot removed as unable to convert to Python 3.

4.17.0 - 2022-12-12

Changed

  • On x86 "vga=current" can now be used together with GrUB2's gfxpayload setting. Note that this requires use of "multiboot2" (and "module2") as the GrUB commands loading Xen.
  • The "gnttab" option now has a new command line sub-option for disabling the GNTTABOP_transfer functionality.
  • The x86 MCE command line option info is now updated.

Added / support upgraded

  • Out-of-tree builds for the hypervisor now supported.
  • __ro_after_init support, for marking data as immutable after boot.
  • The project has officially adopted 4 directives and 24 rules of MISRA-C, added MISRA-C checker build integration, and defined how to document deviations.
  • IOMMU superpage support on x86, affecting PV guests as well as HVM/PVH ones when they don't share page tables with the CPU (HAP / EPT / NPT).
  • Support for VIRT_SSBD and MSR_SPEC_CTRL for HVM guests on AMD.
  • Improved TSC, CPU, and APIC clock frequency calibration on x86.
  • Support for Xen using x86 Control Flow Enforcement technology for its own protection. Both Shadow Stacks (ROP protection) and Indirect Branch Tracking (COP/JOP protection).
  • Add mwait-idle support for SPR and ADL on x86.
  • Extend security support for hosts to 12 TiB of memory on x86.
  • Add command line option to set cpuid parameters for dom0 at boot time on x86.
  • Improved static configuration options on Arm.
  • cpupools can be specified at boot using device tree on Arm.
  • It is possible to use PV drivers with dom0less guests, allowing statically booted dom0less guests with PV devices.
  • On Arm, p2m structures are now allocated out of a pool of memory set aside at domain creation.
  • Improved mitigations against Spectre-BHB on Arm.
  • Support VirtIO-MMIO devices device-tree binding creation in toolstack on Arm.
  • Allow setting the number of CPUs to activate at runtime from command line option on Arm.
  • Grant-table support on Arm was improved and hardened by implementing "simplified M2P-like approach for the xenheap pages"
  • Add Renesas R-Car Gen4 IPMMU-VMSA support on Arm.
  • Add i.MX lpuart and i.MX8QM support on Arm.
  • Improved toolstack build system.
  • Add Xue - console over USB 3 Debug Capability.
  • gitlab-ci automation: Fixes and improvements together with new tests.

Removed / support downgraded

  • dropped support for the (x86-only) "vesa-mtrr" and "vesa-remap" command line options

4.16.0 - 2021-12-02

Removed

  • XENSTORED_ROOTDIR environment variable from configuartion files and initscripts, due to being unused.

Changed

  • Quarantining of passed-through PCI devices no longer defaults to directing I/O to a scratch page, matching original post-XSA-302 behavior (albeit the change was also backported, first appearing in 4.12.2 and 4.11.4). Prior (4.13...4.15-like) behavior can be arranged for either by enabling the IOMMU_QUARANTINE_SCRATCH_PAGE setting at build (configuration) time or by passing "iommu=quarantine=scratch-page" on the hypervisor command line.
  • pv-grub stubdoms will no longer be built per default. In order to be able to use pv-grub configure needs to be called with "--enable-pv-grub" as parameter.
  • qemu-traditional based device models (both, qemu-traditional and ioemu-stubdom) will no longer be built per default. In order to be able to use those, configure needs to be called with "--enable-qemu-traditional" as parameter.
  • Fixes for credit2 scheduler stability in corner case conditions.
  • Ongoing improvements in the hypervisor build system.
  • vtpmmgr miscellaneous fixes in preparation for TPM 2.0 support.
  • 32bit PV guests only supported in shim mode.
  • Improved PVH dom0 debug key handling.
  • Fix booting on some Intel systems without a PIT (i8254).
  • Cleanup of the xenstore library interface.
  • Fix truncation of return value from xencall2 by introducing a new helper that returns a long instead.
  • Fix system register accesses on Arm to use the proper 32/64bit access size.
  • Various fixes for Arm OP-TEE mediator.
  • Switch to domheap for Xen page tables.

Added

  • 32bit Arm builds to the gitlab-ci automated tests.
  • x86 full system tests to the gitlab-ci automated tests.
  • Arm limited vPMU support for guests.
  • Static physical memory allocation for dom0less on arm64.
  • dom0less EFI support on arm64.
  • GICD_ICPENDR register handling in vGIC emulation to support Zephyr OS.
  • CPU feature leveling on arm64 platform with heterogeneous cores.
  • Report unpopulated memory regions safe to use for external mappings, Arm and device tree only.
  • Support of generic DT IOMMU bindings for Arm SMMU v2.
  • Limit grant table version on a per-domain basis.

4.15.0 - 2021-04-08

Added / support upgraded

  • ARM IOREQ servers (device emulation etc.) (Tech Preview)
  • Renesas IPMMU-VMSA (Supported, not security supported; was Tech Preview)
  • ARM SMMUv3 (Tech Preview)
  • Switched MSR accesses to deny by default policy.
  • Intel Processor Trace support (Tech Preview)
  • Named PCI devices for xl/libxl
  • Improved documentation for xl PCI configuration format
  • Support for zstd-compressed dom0 (x86) and domU kernels
  • EFI: Enable booting unified hypervisor/kernel/initrd/DT images
  • Reduce ACPI verbosity by default
  • Add ucode=allow-same option to test late microcode loading path
  • Library improvements from NetBSD ports upstreamed
  • CI loop: Add Alpine Linux, Ubuntu Focal targets; drop CentOS 6
  • CI loop: Add qemu-based dom0 / domU test for ARM
  • CI loop: Add dom0less aarch64 smoke test
  • x86: Allow domains to use AVX-VNNI instructions
  • Factored out HVM-specific shadow code, improving code clarity and reducing the size of PV-only hypervisor builds
  • Added XEN_SCRIPT_DIR configuration option to specify location for Xen scripts, rather than hard-coding /etc/xen/scripts
  • xennet: Documented a way for the backend (or toolstack) to specify MTU to the frontend
  • xenstore can now be live-updated on a running system. (Tech preview)
  • Some additional affordances in various xl subcommands.
  • Added workarounds for the following ARM errata: Cortex A53 #843419, Cortex A55 #1530923, Cortex A72 #853709, Cortex A73 #858921, Cortex A76 #1286807, Neoverse-N1 #1165522
  • On detecting a host crash, some debug key handlers can automatically triggered to aid in debugging
  • Increase the maximum number of guests which can share a single IRQ from 7 to 16, and make this configurable with irq-max-guests

Removed / support downgraded

  • qemu-xen-traditional as host process device model, now "No security support, not recommended". (Use as stub domain device model is still supported - see SUPPORT.md.)

4.14.0 - 2020-07-23

Added

  • This file and MAINTAINERS entry.
  • Use x2APIC mode whenever available, regardless of interrupt remapping support.
  • Performance improvements to guest assisted TLB flushes, either when using the Xen hypercall interface or the viridian one.
  • Assorted pvshim performance and scalability improvements plus some bug fixes.
  • Hypervisor framework to ease porting Xen to run on hypervisors.
  • Initial support to run on Hyper-V.
  • Initial hypervisor file system (hypfs) support.
  • libxl support for running qemu-xen device model in a linux stubdomain.
  • New 'domid_policy', allowing domain-ids to be randomly chosen.
  • Option to preserve domain-id across migrate or save+restore.
  • Support in kdd for initial KD protocol handshake for Win 7, 8 and 10 (64 bit).
  • Tech preview support for Control-flow Execution Technology, with Xen using Supervisor Shadow Stacks for its own protection.

Changed

  • The CPUID data seen by a guest on boot is now moved in the migration stream. A guest migrating between non-identical hardware will now no longer observe details such as Family/Model/Stepping, Cache, etc changing. An administrator still needs to take care to ensure the features visible to the guest at boot are compatible with anywhere it might migrate.

4.13.0 - 2019-12-17

Pointer to release from which CHANGELOG tracking starts