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Re: [PATCH RFC V2 00/37] Support of Virtual CPU Hotplug for ARMv8 Arch
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From: |
Miguel Luis |
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Subject: |
Re: [PATCH RFC V2 00/37] Support of Virtual CPU Hotplug for ARMv8 Arch |
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Date: |
Thu, 12 Oct 2023 17:02:19 +0000 |
Hi Salil,
> On 26 Sep 2023, at 10:03, Salil Mehta <salil.mehta@huawei.com> wrote:
>
> [ *REPEAT: Sent patches got held at internal server yesterday* ]
>
> PROLOGUE
> ========
>
> To assist in review and set the right expectations from this RFC, please first
> read below sections *APPENDED AT THE END* of this cover letter,
>
> 1. Important *DISCLAIMER* [Section (X)]
> 2. Work presented at KVMForum Conference (slides available) [Section (V)F]
> 3. Organization of patches [Section (XI)]
> 4. References [Section (XII)]
> 5. Detailed TODO list of the leftover work or work-in-progress [Section (IX)]
>
> NOTE: There has been an interest shown by other organizations in adapting
> this series for their architecture. I am planning to split this RFC into
> architecture *agnostic* and *specific* patch-sets in subsequent releases. ARM
> specific patch-set will continue as RFC V3 and architecture agnostic patch-set
> will be floated without RFC tag and can be consumed in this Qemu cycle if
> MAINTAINERs ack it.
>
> [Please check section (XI)B for details of architecture agnostic patches]
>
>
> SECTIONS [I - XIII] are as follows :
>
> (I) Key Changes (RFC V1 -> RFC V2)
> ==================================
>
> RFC V1:
> https://lore.kernel.org/qemu-devel/20200613213629.21984-1-salil.mehta@huawei.com/
>
> 1. ACPI MADT Table GIC CPU Interface can now be presented [6] as ACPI
> *online-capable* or *enabled* to the Guest OS at the boot time. This means
> associated CPUs can have ACPI _STA as *enabled* or *disabled* even after
> boot
> See, UEFI ACPI 6.5 Spec, Section 05, Table 5.37 GICC CPU Interface Flags[20]
> 2. SMCC/HVC Hypercall exit handling in userspace/Qemu for PSCI CPU_{ON,OFF}
> request. This is required to {dis}allow online'ing a vCPU.
> 3. Always presenting unplugged vCPUs in CPUs ACPI AML code as ACPI
> _STA.PRESENT
> to the Guest OS. Toggling ACPI _STA.Enabled to give an effect of the
> hot{un}plug.
> 4. Live Migration works (some issues are still there)
> 5. TCG/HVF/qtest does not support Hotplug and falls back to default.
> 6. Code for TCG support do exists in this release (it is a work-in-progress)
> 7. ACPI _OSC method can now be used by OSPM to negotiate Qemu VM platform
> hotplug capability (_OSC Query support still pending)
> 8. Misc. Bug fixes
>
> (II) Summary
> =======
>
> This patch-set introduces the virtual CPU hotplug support for ARMv8
> architecture
> in QEMU. Idea is to be able to hotplug and hot-unplug the vCPUs while guest VM
> is running and no reboot is required. This does *not* makes any assumption of
> the physical CPU hotplug availability within the host system but rather tries
> to
> solve the problem at virtualizer/QEMU layer. Introduces ACPI CPU hotplug hooks
> and event handling to interface with the guest kernel, code to initialize,
> plug
> and unplug CPUs. No changes are required within the host kernel/KVM except the
> support of hypercall exit handling in the user-space/Qemu which has recently
> been added to the kernel. Its corresponding Guest kernel changes have been
> posted on the mailing-list [3] [4] by James Morse.
>
> (III) Motivation
> ==========
>
> This allows scaling the guest VM compute capacity on-demand which would be
> useful for the following example scenarios,
>
> 1. Vertical Pod Autoscaling [9][10] in the cloud: Part of the orchestration
> framework which could adjust resource requests (CPU and Mem requests) for
> the containers in a pod, based on usage.
> 2. Pay-as-you-grow Business Model: Infrastructure provider could allocate and
> restrict the total number of compute resources available to the guest VM
> according to the SLA (Service Level Agreement). VM owner could request for
> more compute to be hot-plugged for some cost.
>
> For example, Kata Container VM starts with a minimum amount of resources (i.e.
> hotplug everything approach). why?
>
> 1. Allowing faster *boot time* and
> 2. Reduction in *memory footprint*
>
> Kata Container VM can boot with just 1 vCPU and then later more vCPUs can be
> hot-plugged as per requirement.
>
> (IV) Terminology
> ===========
>
> (*) Posssible CPUs: Total vCPUs which could ever exist in VM. This includes
> any cold booted CPUs plus any CPUs which could be later
> hot-plugged.
> - Qemu parameter(-smp maxcpus=N)
> (*) Present CPUs: Possible CPUs which are ACPI 'present'. These might or
> might
> not be ACPI 'enabled'.
> - Present vCPUs = Possible vCPUs (Always on ARM Arch)
> (*) Enabled CPUs: Possible CPUs which are ACPI ‘present’ and 'enabled' and
> can
> now be ‘onlined’ (PSCI) for use by Guest Kernel. All cold
> booted vCPUs are ACPI 'enabled' at boot. Later, using
> device_add more vCPUs can be hotplugged and be made ACPI
> 'enabled.
> - Qemu parameter(-smp cpus=N). Can be used to specify some
> cold booted vCPUs during VM init. Some can be added using
> '-device' option.
>
> (V) Constraints Due To ARMv8 CPU Architecture [+] Other Impediments
> ===============================================================
>
> A. Physical Limitation to Support CPU Hotplug: (Architectural Constraint)
> 1. ARMv8 CPU architecture does not support the concept of the physical CPU
> hotplug.
> a. There are many per-CPU components like PMU, SVE, MTE, Arch timers etc.
> whose behaviour need to be clearly defined when CPU is hot(un)plugged.
> There is no specification for this.
>
> 2. Other ARM components like GIC etc. have not been designed to realize
> physical CPU hotplug capability as of now. For example,
> a. Every physical CPU has a unique GICC (GIC CPU Interface) by construct.
> Architecture does not specifies what CPU hot(un)plug would mean in
> context to any of these.
> b. CPUs/GICC are physically connected to unique GICR (GIC Redistributor).
> GIC Redistributors are always part of always-on power domain. Hence,
> cannot be powered-off as per specification.
>
> B. Impediments in Firmware/ACPI (Architectural Constraint)
>
> 1. Firmware has to expose GICC, GICR and other per-CPU features like PMU,
> SVE, MTE, Arch Timers etc. to the OS. Due to architectural constraint
> stated in above section A1(a), all interrupt controller structures of
> MADT describing GIC CPU Interfaces and the GIC Redistibutors MUST be
> presented by firmware to the OSPM during the boot time.
> 2. Architectures that support CPU hotplug can evaluate ACPI _MAT method to
> get this kind of information from the firmware even after boot and the
> OSPM has capability to process these. ARM kernel uses information in MADT
> interrupt controller structures to identify number of Present CPUs during
> boot and hence does not allow to change these after boot. Number of
> present CPUs cannot be changed. It is an architectural constraint!
>
> C. Impediments in KVM to Support Virtual CPU Hotplug (Architectural
> Constraint)
>
> 1. KVM VGIC:
> a. Sizing of various VGIC resources like memory regions etc. related to
> the redistributor happens only once and is fixed at the VM init time
> and cannot be changed later after initialization has happened.
> KVM statically configures these resources based on the number of
> vCPUs
> and the number/size of redistributor ranges.
> b. Association between vCPU and its VGIC redistributor is fixed at the
> VM init time within the KVM i.e. when redistributor iodevs gets
> registered. VGIC does not allows to setup/change this association
> after VM initialization has happened. Physically, every CPU/GICC is
> uniquely connected with its redistributor and there is no
> architectural way to set this up.
> 2. KVM vCPUs:
> a. Lack of specification means destruction of KVM vCPUs does not exist
> as
> there is no reference to tell what to do with other per-vCPU
> components like redistributors, arch timer etc.
> b. Infact, KVM does not implements destruction of vCPUs for any
> architecture. This is independent of the fact whether architecture
> actually supports CPU Hotplug feature. For example, even for x86 KVM
> does not implements destruction of vCPUs.
>
> D. Impediments in Qemu to Support Virtual CPU Hotplug (KVM Constraints->Arch)
>
> 1. Qemu CPU Objects MUST be created to initialize all the Host KVM vCPUs to
> overcome the KVM constraint. KVM vCPUs are created, initialized when Qemu
> CPU Objects are realized. But keepinsg the QOM CPU objects realized for
> 'yet-to-be-plugged' vCPUs can create problems when these new vCPUs shall
> be plugged using device_add and a new QOM CPU object shall be created.
> 2. GICV3State and GICV3CPUState objects MUST be sized over *possible vCPUs*
> during VM init time while QOM GICV3 Object is realized. This is because
> KVM VGIC can only be initialized once during init time. But every
> GICV3CPUState has an associated QOM CPU Object. Later might corresponds
> to
> vCPU which are 'yet-to-be-plugged'(unplugged at init).
> 3. How should new QOM CPU objects be connected back to the GICV3CPUState
> objects and disconnected from it in case CPU is being hot(un)plugged?
> 4. How should 'unplugged' or 'yet-to-be-plugged' vCPUs be represented in the
> QOM for which KVM vCPU already exists? For example, whether to keep,
> a. No QOM CPU objects Or
> b. Unrealized CPU Objects
> 5. How should vCPU state be exposed via ACPI to the Guest? Especially for
> the unplugged/yet-to-be-plugged vCPUs whose CPU objects might not exists
> within the QOM but the Guest always expects all possible vCPUs to be
> identified as ACPI *present* during boot.
> 6. How should Qemu expose GIC CPU interfaces for the unplugged or
> yet-to-beplugged vCPUs using ACPI MADT Table to the Guest?
>
> E. Summary of Approach ([+] Workarounds to problems in sections A, B, C & D)
>
> 1. At VM Init, pre-create all the possible vCPUs in the Host KVM i.e. even
> for the vCPUs which are yet-to-be-plugged in Qemu but keep them in the
> powered-off state.
> 2. After the KVM vCPUs have been initialized in the Host, the KVM vCPU
> objects corresponding to the unplugged/yet-to-be-plugged vCPUs are parked
> at the existing per-VM "kvm_parked_vcpus" list in Qemu. (similar to x86)
> 3. GICV3State and GICV3CPUState objects are sized over possible vCPUs during
> VM init time i.e. when Qemu GIC is realized. This in turn sizes KVM VGIC
> resources like memory regions etc. related to the redistributors with the
> number of possible KVM vCPUs. This never changes after VM has
> initialized.
> 4. Qemu CPU objects corresponding to unplugged/yet-to-be-plugged vCPUs are
> released post Host KVM CPU and GIC/VGIC initialization.
> 5. Build ACPI MADT Table with below updates
> a. Number of GIC CPU interface entries (=possible vCPUs)
> b. Present Boot vCPU as MADT.GICC.Enabled=1 (Not hot[un]pluggable)
> c. Present hot(un)pluggable vCPUs as MADT.GICC.online-capable=1
> - MADT.GICC.Enabled=0 (Mutually exclusive) [6][7]
> - vCPU can be ACPI enabled+onlined after Guest boots (Firmware Policy)
> - Some issues with above (details in later sections)
> 6. Expose below ACPI Status to Guest kernel
> a. Always _STA.Present=1 (all possible vCPUs)
> b. _STA.Enabled=1 (plugged vCPUs)
> c. _STA.Enabled=0 (unplugged vCPUs)
> 7. vCPU hotplug *realizes* new QOM CPU object. Following happens,
> a. Realizes, initializes QOM CPU Object & spawns Qemu vCPU thread
> b. Unparks the existing KVM vCPU ("kvm_parked_vcpus" list)
> - Attaches to QOM CPU object.
> c. Reinitializes KVM vCPU in the Host
> - Resets the core and sys regs, sets defaults etc.
> d. Runs KVM vCPU (created with "start-powered-off")
> - vCPU thread sleeps (waits for vCPU reset via PSCI)
> e. Updates Qemu GIC
> - Wires back IRQs related to this vCPU.
> - GICV3CPUState association with QOM CPU Object.
> f. Updates [6] ACPI _STA.Enabled=1
> g. Notifies Guest about new vCPU (via ACPI GED interface)
> - Guest checks _STA.Enabled=1
> - Guest adds processor (registers CPU with LDM) [3]
> h. Plugs the QOM CPU object in the slot.
> - slot-number = cpu-index{socket,cluster,core,thread}
> i. Guest online's vCPU (CPU_ON PSCI call over HVC/SMC)
> - KVM exits HVC/SMC Hypercall [5] to Qemu (Policy Check).
> - Qemu powers-on KVM vCPU in the Host
> 8. vCPU hot-unplug *unrealizes* QOM CPU Object. Following happens,
> a. Notifies Guest (via ACPI GED interface) vCPU hot-unplug event
> - Guest offline's vCPU (CPU_OFF PSCI call over HVC/SMC)
> b. KVM exits HVC/SMC Hypercall [5] to Qemu (Policy Check).
> - Qemu powers-off the KVM vCPU in the Host
> c Guest signals *Eject* vCPU to Qemu
> d. Qemu updates [6] ACPI _STA.Enabled=0
> e. Updates GIC
> - Un-wires IRQs related to this vCPU
> - GICV3CPUState association with new QOM CPU Object is updated.
> f. Unplugs the vCPU
> - Removes from slot
> - Parks KVM vCPU ("kvm_parked_vcpus" list)
> - Unrealizes QOM CPU Object & joins back Qemu vCPU thread
> - Destroys QOM CPU object
> g. Guest checks ACPI _STA.Enabled=0
> - Removes processor (unregisters CPU with LDM) [3]
>
> F. Work Presented at KVM Forum Conferences:
> Details of above work has been presented at KVMForum2020 and KVMForum2023
> conferences. Slides are available at below links,
> a. KVMForum 2023
> - Challenges Revisited in Supporting Virt CPU Hotplug on architectures
> that don't Support CPU Hotplug (like ARM64)
> https://kvm-forum.qemu.org/2023/talk/9SMPDQ/
> b. KVMForum 2020
> - Challenges in Supporting Virtual CPU Hotplug on SoC Based Systems
> (like ARM64) - Salil Mehta, Huawei
> https://sched.co/eE4m
>
> (VI) Commands Used
> =============
>
> A. Qemu launch commands to init the machine
>
> $ qemu-system-aarch64 --enable-kvm -machine virt,gic-version=3 \
> -cpu host -smp cpus=4,maxcpus=6 \
> -m 300M \
> -kernel Image \
> -initrd rootfs.cpio.gz \
> -append "console=ttyAMA0 root=/dev/ram rdinit=/init maxcpus=2 acpi=force" \
> -nographic \
> -bios QEMU_EFI.fd \
>
> B. Hot-(un)plug related commands
>
> # Hotplug a host vCPU(accel=kvm)
> $ device_add host-arm-cpu,id=core4,core-id=4
>
> # Hotplug a vCPU(accel=tcg)
> $ device_add cortex-a57-arm-cpu,id=core4,core-id=4
>
> # Delete the vCPU
> $ device_del core4
>
> Sample output on guest after boot:
>
> $ cat /sys/devices/system/cpu/possible
> 0-5
> $ cat /sys/devices/system/cpu/present
> 0-5
> $ cat /sys/devices/system/cpu/enabled
> 0-3
> $ cat /sys/devices/system/cpu/online
> 0-1
> $ cat /sys/devices/system/cpu/offline
> 2-5
>
> Sample output on guest after hotplug of vCPU=4:
>
> $ cat /sys/devices/system/cpu/possible
> 0-5
> $ cat /sys/devices/system/cpu/present
> 0-5
> $ cat /sys/devices/system/cpu/enabled
> 0-4
> $ cat /sys/devices/system/cpu/online
> 0-1,4
> $ cat /sys/devices/system/cpu/offline
> 2-3,5
>
> Note: vCPU=4 was explicitly 'onlined' after hot-plug
> $ echo 1 > /sys/devices/system/cpu/cpu4/online
>
> (VII) Repository
> ==========
>
> (*) QEMU changes for vCPU hotplug could be cloned from below site,
> https://github.com/salil-mehta/qemu.git virt-cpuhp-armv8/rfc-v2
> (*) Guest Kernel changes (by James Morse, ARM) are available here:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git
> virtual_cpu_hotplug/rfc/v2
>
>
> (VIII) KNOWN ISSUES
> ============
>
> 1. Migration has been lightly tested. Below are some of the known issues:
> - Ocassional CPU stall (not always repeatable)
> - Negative test case like asymmetric source/destination VM config causes
> dump.
> - Migration with TCG is not working properly.
> 2. TCG with Single threaded mode is broken.
> 3. HVF and qtest support is broken.
> 4. ACPI MADT Table flags [7] MADT.GICC.Enabled and MADT.GICC.online-capable
> are
> mutually exclusive i.e. as per the change [6] a vCPU cannot be both
> GICC.Enabled and GICC.online-capable. This means,
> [ Link: https://bugzilla.tianocore.org/show_bug.cgi?id=3706 ]
> a. If we have to support hot-unplug of the cold-booted vCPUs then these MUST
> be specified as GICC.online-capable in the MADT Table during boot by the
> firmware/Qemu. But this requirement conflicts with the requirement to
> support new Qemu changes with legacy OS which dont understand
> MADT.GICC.online-capable Bit. Legacy OS during boot time will ignore this
> bit and hence these vCPUs will not appear on such OS. This is unexpected
> behaviour.
> b. In case we decide to specify vCPUs as MADT.GICC.Enabled and try to unplug
> these cold-booted vCPUs from OS (which in actual should be blocked by
> returning error at Qemu) then features like 'kexec' will break.
> c. As I understand, removal of the cold-booted vCPUs is a required feature
> and x86 world allows it.
> d. Hence, either we need a specification change to make the
> MADT.GICC.Enabled
> and MADT.GICC.online-capable Bits NOT mutually exclusive or NOT support
> removal of cold-booted vCPUs. In the later case, a check can be
> introduced
> to bar the users from unplugging vCPUs, which were cold-booted, using QMP
> commands. (Needs discussion!)
> Please check below patch part of this patch-set:
> [hw/arm/virt: Expose cold-booted CPUs as MADT GICC Enabled]
> 5. Code related to the notification to GICV3 about hot(un)plug of a vCPU event
> might need further discussion.
>
>
> (IX) THINGS TO DO
> ============
>
> 1. Fix the Migration Issues
> 2. Fix issues related to TCG/Emulation support.
> 3. Comprehensive Testing. Current testing is very basic.
> a. Negative Test cases
> 4. Qemu Documentation(.rst) need to be updated.
> 5. Fix qtest, HVF Support
> 6. Fix the design issue related to ACPI MADT.GICC flags discussed in known
> issues. This might require UEFI ACPI specification change!
> 7. Add ACPI _OSC 'Query' support. Only part of _OSC support exists now.
>
> Above is *not* a complete list. Will update later!
>
> Best regards
> Salil.
>
> (X) DISCLAIMER
> ==========
>
> This work is an attempt to present a proof-of-concept of the ARM64 vCPU
> hotplug
> implementation to the community. This is *not* a production level code and
> might
> have bugs. Only a basic testing has been done on HiSilicon Kunpeng920 SoC for
> servers. Once the design and core idea behind the implementation has been
> verified more efforts can be put to harden the code.
>
> This work is *mostly* in the lines of the discussions which have happened in
> the
> previous years[see refs below] across different channels like mailing-list,
> Linaro Open Discussions platform, various conferences like KVMFourm etc. This
> RFC is being used as a way to verify the idea mentioned in this cover-letter
> and
> to get community views. Once this has been agreed, a formal patch shall be
> posted to the mailing-list for review.
>
> [The concept being presented has been found to work!]
>
> (XI) ORGANIZATION OF PATCHES
> =======================
>
> A. All patches [Architecture 'agnostic' + 'specific']:
>
> [Patch 1-9, 23, 36] logic required during machine init
> (*) Some validation checks
> (*) Introduces core-id property and some util functions required later.
> (*) Refactors Parking logic of vCPUs
> (*) Logic to pre-create vCPUs
> (*) GIC initialization pre-sized with possible vCPUs.
> (*) Some refactoring to have common hot and cold plug logic together.
> (*) Release of disable QOM CPU objects in post_cpu_init()
> (*) Support of ACPI _OSC method to negotiate platform hotplug capabilities
> [Patch 10-22] logic related to ACPI at machine init time
> (*) Changes required to Enable ACPI for cpu hotplug
> (*) Initialization ACPI GED framework to cater CPU Hotplug Events
> (*) Build ACPI AML related to CPU control dev
> (*) ACPI MADT/MAT changes
> [Patch 24-35] Logic required during vCPU hot-(un)plug
> (*) Basic framework changes to suppport vCPU hot-(un)plug
> (*) ACPI GED changes for hot-(un)plug hooks.
> (*) wire-unwire the IRQs
> (*) GIC notification logic
> (*) ARMCPU unrealize logic
> (*) Handling of SMCC Hypercall Exits by KVM to Qemu
>
> B. Architecture *agnostic* patches part of patch-set:
>
> [Patch 5,9,11,13,16,20,24,31,33] Common logic to support hotplug
> (*) Refactors Parking logic of vCPUs
> (*) Introduces ACPI GED Support for vCPU Hotplug Events
> (*) Introduces ACPI AML change for CPU Control Device
>
> (XII) REFERENCES
> ==========
>
> [1]
> https://lore.kernel.org/qemu-devel/20200613213629.21984-1-salil.mehta@huawei.com/
> [2]
> https://lore.kernel.org/linux-arm-kernel/20200625133757.22332-1-salil.mehta@huawei.com/
> [3] https://lore.kernel.org/lkml/20230203135043.409192-1-james.morse@arm.com/
> [4] https://lore.kernel.org/all/20230913163823.7880-1-james.morse@arm.com/
> [5]
> https://lore.kernel.org/all/20230404154050.2270077-1-oliver.upton@linux.dev/
> [6] https://bugzilla.tianocore.org/show_bug.cgi?id=3706
> [7]
> https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#gic-cpu-interface-gicc-structure
> [8] https://bugzilla.tianocore.org/show_bug.cgi?id=4481#c5
> [9]
> https://cloud.google.com/kubernetes-engine/docs/concepts/verticalpodautoscaler
> [10]
> https://docs.aws.amazon.com/eks/latest/userguide/vertical-pod-autoscaler.html
> [11] https://lkml.org/lkml/2019/7/10/235
> [12] https://lists.cs.columbia.edu/pipermail/kvmarm/2018-July/032316.html
> [13] https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg06517.html
> [14]
> https://op-lists.linaro.org/archives/list/linaro-open-discussions@op-lists.linaro.org/thread/7CGL6JTACPUZEYQC34CZ2ZBWJGSR74WE/
> [15] http://lists.nongnu.org/archive/html/qemu-devel/2018-07/msg01168.html
> [16] https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00131.html
> [17]
> https://op-lists.linaro.org/archives/list/linaro-open-discussions@op-lists.linaro.org/message/X74JS6P2N4AUWHHATJJVVFDI2EMDZJ74/
> [18]
> https://lore.kernel.org/lkml/20210608154805.216869-1-jean-philippe@linaro.org/
> [19] https://lore.kernel.org/all/20230913163823.7880-1-james.morse@arm.com/
> [20]
> https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#gicc-cpu-interface-flags
>
> (XIII) ACKNOWLEDGEMENTS
> ================
>
> I would like to take this opportunity to thank below people for various
> discussions with me over different channels during the development:
>
> Marc Zyngier (Google) Catalin Marinas (ARM),
> James Morse(ARM), Will Deacon (Google),
> Jean-Phillipe Brucker (Linaro), Sudeep Holla (ARM),
> Lorenzo Pieralisi (Linaro), Gavin Shan (Redhat),
> Jonathan Cameron (Huawei), Darren Hart (Ampere),
> Igor Mamedov (Redhat), Ilkka Koskinen (Ampere),
> Andrew Jones (Redhat), Karl Heubaum (Oracle),
> Keqian Zhu (Huawei), Miguel Luis (Oracle),
> Xiongfeng Wang (Huawei), Vishnu Pajjuri (Ampere),
> Shameerali Kolothum (Huawei) Russell King (Oracle)
> Xuwei/Joy (Huawei), Peter Maydel (Linaro)
> Zengtao/Prime (Huawei), And all those whom I have missed!
>
> Many thanks to below people for their current or past contributions:
>
> 1. James Morse (ARM)
> (Current Kernel part of vCPU Hotplug Support on AARCH64)
> 2. Jean-Philippe Brucker (Linaro)
> (Protoyped one of the earlier PSCI based POC [17][18] based on RFC V1)
> 3. Keqian Zhu (Huawei)
> (Co-developed Qemu prototype)
> 4. Xiongfeng Wang (Huawei)
> (Co-developed earlier kernel prototype)
> 5. Vishnu Pajjuri (Ampere)
> (Verification on Ampere ARM64 Platforms + fixes)
> 6. Miguel Luis (Oracle)
> (Verification on Oracle ARM64 Platforms + fixes)
>
>
> Author Salil Mehta (1):
> target/arm/kvm,tcg: Register/Handle SMCCC hypercall exits to VMM/Qemu
>
> Jean-Philippe Brucker (2):
> hw/acpi: Make _MAT method optional
> target/arm/kvm: Write CPU state back to KVM on reset
>
> Miguel Luis (1):
> tcg/mttcg: enable threads to unregister in tcg_ctxs[]
>
> Salil Mehta (33):
> arm/virt,target/arm: Add new ARMCPU {socket,cluster,core,thread}-id property
> cpus-common: Add common CPU utility for possible vCPUs
> hw/arm/virt: Move setting of common CPU properties in a function
> arm/virt,target/arm: Machine init time change common to vCPU {cold|hot}-plug
> accel/kvm: Extract common KVM vCPU {creation,parking} code
> arm/virt,kvm: Pre-create disabled possible vCPUs @machine init
> arm/virt,gicv3: Changes to pre-size GIC with possible vcpus @machine init
> arm/virt: Init PMU at host for all possible vcpus
> hw/acpi: Move CPU ctrl-dev MMIO region len macro to common header file
> arm/acpi: Enable ACPI support for vcpu hotplug
> hw/acpi: Add ACPI CPU hotplug init stub
> hw/acpi: Use qemu_present_cpu() API in ACPI CPU hotplug init
> hw/acpi: Init GED framework with cpu hotplug events
> arm/virt: Add cpu hotplug events to GED during creation
> arm/virt: Create GED dev before *disabled* CPU Objs are destroyed
> hw/acpi: Update CPUs AML with cpu-(ctrl)dev change
> arm/virt/acpi: Build CPUs AML with CPU Hotplug support
> arm/virt: Make ARM vCPU *present* status ACPI *persistent*
> hw/acpi: ACPI/AML Changes to reflect the correct _STA.{PRES,ENA} Bits to
> Guest
> hw/acpi: Update GED _EVT method AML with cpu scan
> hw/arm: MADT Tbl change to size the guest with possible vCPUs
> arm/virt: Release objects for *disabled* possible vCPUs after init
> hw/acpi: Update ACPI GED framework to support vCPU Hotplug
> arm/virt: Add/update basic hot-(un)plug framework
> arm/virt: Changes to (un)wire GICC<->vCPU IRQs during hot-(un)plug
> hw/arm,gicv3: Changes to update GIC with vCPU hot-plug notification
> hw/intc/arm-gicv3*: Changes required to (re)init the vCPU register info
> arm/virt: Update the guest(via GED) about CPU hot-(un)plug events
> hw/arm: Changes required for reset and to support next boot
> physmem,gdbstub: Common helping funcs/changes to *unrealize* vCPU
> target/arm: Add support of *unrealize* ARMCPU during vCPU Hot-unplug
> hw/arm: Support hotplug capability check using _OSC method
> hw/arm/virt: Expose cold-booted CPUs as MADT GICC Enabled
>
> accel/kvm/kvm-all.c | 61 +-
> accel/tcg/tcg-accel-ops-mttcg.c | 1 +
> cpus-common.c | 37 ++
> gdbstub/gdbstub.c | 13 +
> hw/acpi/acpi-cpu-hotplug-stub.c | 6 +
> hw/acpi/cpu.c | 91 ++-
> hw/acpi/generic_event_device.c | 33 +
> hw/arm/Kconfig | 1 +
> hw/arm/boot.c | 2 +-
> hw/arm/virt-acpi-build.c | 110 +++-
> hw/arm/virt.c | 863 ++++++++++++++++++++-----
> hw/core/gpio.c | 2 +-
> hw/i386/acpi-build.c | 2 +-
> hw/intc/arm_gicv3.c | 1 +
> hw/intc/arm_gicv3_common.c | 66 +-
> hw/intc/arm_gicv3_cpuif.c | 265 ++++----
> hw/intc/arm_gicv3_cpuif_common.c | 5 +
> hw/intc/arm_gicv3_kvm.c | 39 +-
> hw/intc/gicv3_internal.h | 2 +
> include/exec/cpu-common.h | 8 +
> include/exec/gdbstub.h | 1 +
> include/hw/acpi/cpu.h | 7 +-
> include/hw/acpi/cpu_hotplug.h | 4 +
> include/hw/acpi/generic_event_device.h | 5 +
> include/hw/arm/boot.h | 2 +
> include/hw/arm/virt.h | 10 +-
> include/hw/core/cpu.h | 77 +++
> include/hw/intc/arm_gicv3_common.h | 23 +
> include/hw/qdev-core.h | 2 +
> include/sysemu/kvm.h | 2 +
> include/tcg/tcg.h | 1 +
> softmmu/physmem.c | 25 +
> target/arm/arm-powerctl.c | 51 +-
> target/arm/cpu-qom.h | 3 +
> target/arm/cpu.c | 112 ++++
> target/arm/cpu.h | 17 +
> target/arm/cpu64.c | 15 +
> target/arm/gdbstub.c | 6 +
> target/arm/helper.c | 27 +-
> target/arm/internals.h | 12 +-
> target/arm/kvm.c | 93 ++-
> target/arm/kvm64.c | 59 +-
> target/arm/kvm_arm.h | 24 +
> target/arm/meson.build | 1 +
> target/arm/{tcg => }/psci.c | 8 +
> target/arm/tcg/meson.build | 4 -
> tcg/tcg.c | 23 +
> 47 files changed, 1873 insertions(+), 349 deletions(-)
> rename target/arm/{tcg => }/psci.c (97%)
>
Tested on Oracle platforms with Ampere processors.
vCPU hotplug/unplug features along VM live migration.
Please feel free to add,
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Thanks,
Miguel
> --
> 2.34.1
>