Hello,
Please ignore this patch-set as there was some issue w.r.t x86. Details are in
the V3 patch-set sent for review today. V3 has fixed almost all of the issues
identified by Igor in the V1 patch-set in relation to x86.
Please have a look at the below V3 patch-set:
[PATCH V3 0/5] Arch agnostic ACPI changes to support vCPU Hotplug (on Archs like ARM)
https://lore.kernel.org/qemu-devel/20241103102419.202225-1-salil.mehta@huawei.com/#t
Sorry for any inconvenience above might have caused.
Best regards
Salil.
> -----Original Message-----
> From: Salil Mehta <salil.mehta@huawei.com>
> Sent: Thursday, October 31, 2024 8:05 PM
> To: qemu-devel@nongnu.org; qemu-arm@nongnu.org; mst@redhat.com
> Cc: Salil Mehta <salil.mehta@huawei.com>; maz@kernel.org; jean-
> philippe@linaro.org; Jonathan Cameron
> <jonathan.cameron@huawei.com>; lpieralisi@kernel.org;
> peter.maydell@linaro.org; richard.henderson@linaro.org;
> imammedo@redhat.com; andrew.jones@linux.dev; david@redhat.com;
> philmd@linaro.org; peterx@redhat.com; eric.auger@redhat.com;
> will@kernel.org; ardb@kernel.org; oliver.upton@linux.dev;
> pbonzini@redhat.com; gshan@redhat.com; rafael@kernel.org;
> borntraeger@linux.ibm.com; alex.bennee@linaro.org; npiggin@gmail.com;
> harshpb@linux.ibm.com; linux@armlinux.org.uk;
> darren@os.amperecomputing.com; ilkka@os.amperecomputing.com;
> vishnu@os.amperecomputing.com; karl.heubaum@oracle.com;
> miguel.luis@oracle.com; salil.mehta@opnsrc.net; zhukeqian
> <zhukeqian1@huawei.com>; wangxiongfeng (C)
> <wangxiongfeng2@huawei.com>; wangyanan (Y)
> <wangyanan55@huawei.com>; jiakernel2@gmail.com;
> maobibo@loongson.cn; lixianglai@loongson.cn; shahuang@redhat.com;
> zhao1.liu@intel.com; Linuxarm <linuxarm@huawei.com>;
> gustavo.romero@linaro.org
> Subject: [PATCH V2 0/6] Arch agnostic ACPI changes to support vCPU
> Hotplug (on Archs like ARM)
>
> Change Log
> ==========
>
> Patch V1 -> V2:
> 1. Addressed Igor Mammedov's (Redhat) raised issues:
> - Removed `ACPICPUstatus::is_present` State and its handling in the
> ACPI APUs AML code and now all QOM vCPUs are present.
> - Dropped the concept of `acpi_persistent` because now QOM vCPUs
> states and the ACPI vCPU states are consistent.
> - QOM vCPU objects are always present now (accompanying RFC V6)
> - Added .needed() hook to the GED VMSD toconditionally migrate the
> ACPI CPU hotplug state at the source VM.
> 2. Addressed Zhao Liu's (Intel) reported x86 DSDT Table bios-acpi-test failure
> 3. Incorporated Gustavo Romero's comments and added his Tag to [Patches
> 1,2,4] 4. Addressed Gavin Shan's comment to reduce the inline code
> comments
> wherever possible.
>
>
> Brief Recall
> ============
> With the advent of multi-core SoCs, the concept of CPU-level hotplugging
> has become less distinct, often functioning as a power on/off event
> rather than a full hotplug operation. However, hotplug support at the
> die/NUMA/socket level remains meaningful and is architecture-specific.
> Virtual CPU hotplug can be supported regardless of architectural support
> for physical CPU hotplug, as it serves resource management needs—such as
> dynamically scaling VM compute capacity based on demand or SLAs,
> optimizing boot times, or reducing memory footprint. Although, its
> desing must be scalable and must co-exist with future die/NUMA/socket
> level hotplug features.
>
>
> Motivation for this patch-set
> =============================
> In architectures that support vCPU hotplug, firmware or the VMM/QEMU
> typically reflects vCPU status changes to the OS via the ACPI
> `_STA.Present` bit. However, certain CPU architectures prohibit [1]
> modifications to CPU presence after kernel boot. This restriction [2][3]
> could be due to closely integrated per-CPU components—like interrupt
> controllers or other features— that may not support reconfiguration
> post-boot and are often in an `always-on` power domain. Consequently,
> specifications for these architectures require all CPUs to remain
> present i.e.`_STA.Present=True`, once the system is initialized.
>
> To be able to support vCPU Hotplug feature, as a workaround to the above
> limitation, ACPI method `_STA.Enabled` Bit could be used to reflect the
> plugged and unplugged states of the QOM vCPUs.
>
> This patch set introduces the following changes:
>
> 1. Explicit `ACPICPUstatus::is_enabled` State: Adds an `is_enabled`
> state, initialized during machine setup and updated during CPU
> hotplug and hot-unplug events.
>
> 2. Support for Migrating ACPI CPU State: Facilitates the migration of
> the ACPI CPU state. (This needs reconsideration as per Igor. Last
> patch can be dropped if this affects the acceptability of other
> patches of this patch-set)
>
> 3. Updates the Qtest bios-acpi-test
>
> This patch set is designed to work independently and is meant to ensures
> compatibility with existing hotplug support across different
> architectures. This patch-set has been tested alongside ARM-specific
> vCPU hotplug changes (included in the upcoming RFC V6 [4]), and
> hot(un)plug functionalities performed as expected which concerns this
> patch-set. Please have a look.
>
> Thank you!
>
>
> Repository of this patch-set
> ============================
> (*) Latest Architecture Agnostic ACPI changes patch-set:
> https://github.com/salil-mehta/qemu.git virt-cpuhp-armv8/rfc-
> v6.arch.agnostic.acpi.v2
> Link: https://github.com/salil-mehta/qemu/commits/virt-cpuhp-
> armv8/rfc-v6.arch.agnostic.acpi.v2
> (*) Works with upcoming ARM architecture specific patch-set RFC V6 [4]
>
>
> References
> ==========
> [1] Check comment 5 in the bugzilla entry
> Link: https://bugzilla.tianocore.org/show_bug.cgi?id=4481#c5
> [2] KVMForum 2023 Presentation: Challenges Revisited in Supporting Virt
> CPU Hotplug on
> architectures that don’t Support CPU Hotplug (like ARM64)
> a. Kernel Link: https://kvm-forum.qemu.org/2023/KVM-forum-cpu-
> hotplug_7OJ1YyJ.pdf
> b. Qemu Link: https://kvm-
> forum.qemu.org/2023/Challenges_Revisited_in_Supporting_Virt_CPU_Hot
> plug_-__ii0iNb3.pdf
> [3] KVMForum 2020 Presentation: Challenges in Supporting Virtual CPU
> Hotplug on
> SoC Based Systems (like ARM64)
> Link: https://kvmforum2020.sched.com/event/eE4m
> [4] Upcoming RFC V6, Support of Virtual CPU Hotplug for ARMv8 Arch
> Link: https://github.com/salil-mehta/qemu/commits/virt-cpuhp-
> armv8/rfc-v6-rc4
>
>
> Salil Mehta (6):
> hw/acpi: Introduce `is_enabled` state in ACPI CPU Hotplug Status
> hw/acpi: Update ACPI CPU Hotplug state during vCPU hot(un)plug
> qtest: allow ACPI DSDT Table changes
> hw/acpi: Update CPUs AML's `is_enabled` state in ACPI _STA method
> tests/qtest/bios-tables-test: Update DSDT golden masters for
> x86/{pc,q35}
> hw/acpi: Update GED with vCPU Hotplug VMSD for migration
>
> hw/acpi/cpu.c | 22 ++++++++++++++++--
> hw/acpi/generic_event_device.c | 19 +++++++++++++++
> include/hw/acpi/cpu.h | 2 +-
> tests/data/acpi/x86/pc/DSDT | Bin 8527 -> 8533 bytes
> tests/data/acpi/x86/pc/DSDT.acpierst | Bin 8438 -> 8444 bytes
> tests/data/acpi/x86/pc/DSDT.acpihmat | Bin 9852 -> 9858 bytes
> tests/data/acpi/x86/pc/DSDT.bridge | Bin 15398 -> 15404 bytes
> tests/data/acpi/x86/pc/DSDT.cphp | Bin 8991 -> 8997 bytes
> tests/data/acpi/x86/pc/DSDT.dimmpxm | Bin 10181 -> 10187 bytes
> tests/data/acpi/x86/pc/DSDT.hpbridge | Bin 8478 -> 8484 bytes
> tests/data/acpi/x86/pc/DSDT.hpbrroot | Bin 5034 -> 5040 bytes
> tests/data/acpi/x86/pc/DSDT.ipmikcs | Bin 8599 -> 8605 bytes
> tests/data/acpi/x86/pc/DSDT.memhp | Bin 9886 -> 9892 bytes
> tests/data/acpi/x86/pc/DSDT.nohpet | Bin 8385 -> 8391 bytes
> tests/data/acpi/x86/pc/DSDT.numamem | Bin 8533 -> 8539 bytes
> tests/data/acpi/x86/pc/DSDT.roothp | Bin 12320 -> 12326 bytes
> tests/data/acpi/x86/q35/DSDT | Bin 8355 -> 8361 bytes
> tests/data/acpi/x86/q35/DSDT.acpierst | Bin 8372 -> 8378 bytes
> tests/data/acpi/x86/q35/DSDT.acpihmat | Bin 9680 -> 9686 bytes
> .../acpi/x86/q35/DSDT.acpihmat-noinitiator | Bin 8634 -> 8640 bytes
> tests/data/acpi/x86/q35/DSDT.applesmc | Bin 8401 -> 8407 bytes
> tests/data/acpi/x86/q35/DSDT.bridge | Bin 11968 -> 11974 bytes
> tests/data/acpi/x86/q35/DSDT.core-count | Bin 12913 -> 12919 bytes
> tests/data/acpi/x86/q35/DSDT.core-count2 | Bin 33770 -> 33776 bytes
> tests/data/acpi/x86/q35/DSDT.cphp | Bin 8819 -> 8825 bytes
> tests/data/acpi/x86/q35/DSDT.cxl | Bin 13148 -> 13154 bytes
> tests/data/acpi/x86/q35/DSDT.dimmpxm | Bin 10009 -> 10015 bytes
> tests/data/acpi/x86/q35/DSDT.ipmibt | Bin 8430 -> 8436 bytes
> tests/data/acpi/x86/q35/DSDT.ipmismbus | Bin 8443 -> 8449 bytes
> tests/data/acpi/x86/q35/DSDT.ivrs | Bin 8372 -> 8378 bytes
> tests/data/acpi/x86/q35/DSDT.memhp | Bin 9714 -> 9720 bytes
> tests/data/acpi/x86/q35/DSDT.mmio64 | Bin 9485 -> 9491 bytes
> tests/data/acpi/x86/q35/DSDT.multi-bridge | Bin 13208 -> 13214 bytes
> tests/data/acpi/x86/q35/DSDT.noacpihp | Bin 8235 -> 8241 bytes
> tests/data/acpi/x86/q35/DSDT.nohpet | Bin 8213 -> 8219 bytes
> tests/data/acpi/x86/q35/DSDT.numamem | Bin 8361 -> 8367 bytes
> tests/data/acpi/x86/q35/DSDT.pvpanic-isa | Bin 8456 -> 8462 bytes
> tests/data/acpi/x86/q35/DSDT.thread-count | Bin 12913 -> 12919 bytes
> tests/data/acpi/x86/q35/DSDT.thread-count2 | Bin 33770 -> 33776 bytes
> tests/data/acpi/x86/q35/DSDT.tis.tpm12 | Bin 8961 -> 8967 bytes
> tests/data/acpi/x86/q35/DSDT.tis.tpm2 | Bin 8987 -> 8993 bytes
> tests/data/acpi/x86/q35/DSDT.type4-count | Bin 18589 -> 18595 bytes
> tests/data/acpi/x86/q35/DSDT.viot | Bin 14615 -> 14621 bytes
> tests/data/acpi/x86/q35/DSDT.xapic | Bin 35718 -> 35724 bytes
> 44 files changed, 40 insertions(+), 3 deletions(-)
>
> --
> 2.34.1
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