From: Salil Mehta via <qemu-devel@nongnu.org>
To: <qemu-devel@nongnu.org>, <qemu-arm@nongnu.org>, <mst@redhat.com>
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<gustavo.romero@linaro.org>
Subject: [PATCH V3 0/5] Arch agnostic ACPI changes to support vCPU Hotplug (on Archs like ARM)
Date: Sun, 3 Nov 2024 10:24:14 +0000 [thread overview]
Message-ID: <20241103102419.202225-1-salil.mehta@huawei.com> (raw)
Change Log
==========
Patch V2 -> V3:
1. Addressed left over issues of x86 suggested by Igor Mammedov (Redhat):
- Removed the `ACPICPUstatus::is_enabled` State as well as it was
breaking the x86 migration
- Above is in addition to `is_present` state which was removed in V2
- Dropped [PATCH 1/6] of V2 patch-set
- Introduced hooks `CPUClass::cpu_{persistence,enabled}_status()`
2. Fixed the accidental CPUs AML break of x86 in V2 (sorry for this!).
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. Introduces`CPUClass::cpu_{persistence,enabled}_status` hooks: To
check if the CPU should always remain present even after unplug
operation and to fetch the vCPU `enabled` status in case it is
present. Later is used in context when Guest Kernel evaluates
ACPI `_STA` method and the status is read from the flags stored
in the Qemu ACPI code.
2. Support for Migrating ACPI CPU Hotplug State: Facilitates the
migration of the ACPI CPU hotplug state in VMSD by conditonally
making it part of the GED VMSD.
3. Updates the Qtest bios-acpi-tables/DSDT binaries for x86/{pc,q35}
This patch set is designed to work independently and is meant to ensure
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:
Repo: https://github.com/salil-mehta/qemu.git virt-cpuhp-armv8/rfc-v6.arch.agnostic.acpi.v3
Link: https://github.com/salil-mehta/qemu/commits/virt-cpuhp-armv8/rfc-v6.arch.agnostic.acpi.v3
(*) Works with upcoming ARM architecture specific patch-set RFC V6-rc5 [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_Hotplug_-__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-rc5
Salil Mehta (5):
hw/acpi: Make CPUs ACPI `presence` conditional during vCPU hot-unplug
qtest: allow ACPI DSDT Table changes
hw/acpi: Update ACPI `_STA` method with QOM vCPU ACPI Hotplug states
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 | 53 ++++++++++++++++--
hw/acpi/generic_event_device.c | 19 +++++++
include/hw/core/cpu.h | 2 +
tests/data/acpi/x86/pc/DSDT | Bin 8527 -> 8561 bytes
tests/data/acpi/x86/pc/DSDT.acpierst | Bin 8438 -> 8472 bytes
tests/data/acpi/x86/pc/DSDT.acpihmat | Bin 9852 -> 9886 bytes
tests/data/acpi/x86/pc/DSDT.bridge | Bin 15398 -> 15432 bytes
tests/data/acpi/x86/pc/DSDT.cphp | Bin 8991 -> 9025 bytes
tests/data/acpi/x86/pc/DSDT.dimmpxm | Bin 10181 -> 10215 bytes
tests/data/acpi/x86/pc/DSDT.hpbridge | Bin 8478 -> 8512 bytes
tests/data/acpi/x86/pc/DSDT.hpbrroot | Bin 5034 -> 5068 bytes
tests/data/acpi/x86/pc/DSDT.ipmikcs | Bin 8599 -> 8633 bytes
tests/data/acpi/x86/pc/DSDT.memhp | Bin 9886 -> 9920 bytes
tests/data/acpi/x86/pc/DSDT.nohpet | Bin 8385 -> 8419 bytes
tests/data/acpi/x86/pc/DSDT.numamem | Bin 8533 -> 8567 bytes
tests/data/acpi/x86/pc/DSDT.roothp | Bin 12320 -> 12354 bytes
tests/data/acpi/x86/q35/DSDT | Bin 8355 -> 8389 bytes
tests/data/acpi/x86/q35/DSDT.acpierst | Bin 8372 -> 8406 bytes
tests/data/acpi/x86/q35/DSDT.acpihmat | Bin 9680 -> 9714 bytes
.../acpi/x86/q35/DSDT.acpihmat-noinitiator | Bin 8634 -> 8668 bytes
tests/data/acpi/x86/q35/DSDT.applesmc | Bin 8401 -> 8435 bytes
tests/data/acpi/x86/q35/DSDT.bridge | Bin 11968 -> 12002 bytes
tests/data/acpi/x86/q35/DSDT.core-count | Bin 12913 -> 12947 bytes
tests/data/acpi/x86/q35/DSDT.core-count2 | Bin 33770 -> 33804 bytes
tests/data/acpi/x86/q35/DSDT.cphp | Bin 8819 -> 8853 bytes
tests/data/acpi/x86/q35/DSDT.cxl | Bin 13148 -> 13182 bytes
tests/data/acpi/x86/q35/DSDT.dimmpxm | Bin 10009 -> 10043 bytes
tests/data/acpi/x86/q35/DSDT.ipmibt | Bin 8430 -> 8464 bytes
tests/data/acpi/x86/q35/DSDT.ipmismbus | Bin 8443 -> 8477 bytes
tests/data/acpi/x86/q35/DSDT.ivrs | Bin 8372 -> 8406 bytes
tests/data/acpi/x86/q35/DSDT.memhp | Bin 9714 -> 9748 bytes
tests/data/acpi/x86/q35/DSDT.mmio64 | Bin 9485 -> 9519 bytes
tests/data/acpi/x86/q35/DSDT.multi-bridge | Bin 13208 -> 13242 bytes
tests/data/acpi/x86/q35/DSDT.noacpihp | Bin 8235 -> 8269 bytes
tests/data/acpi/x86/q35/DSDT.nohpet | Bin 8213 -> 8247 bytes
tests/data/acpi/x86/q35/DSDT.numamem | Bin 8361 -> 8395 bytes
tests/data/acpi/x86/q35/DSDT.pvpanic-isa | Bin 8456 -> 8490 bytes
tests/data/acpi/x86/q35/DSDT.thread-count | Bin 12913 -> 12947 bytes
tests/data/acpi/x86/q35/DSDT.thread-count2 | Bin 33770 -> 33804 bytes
tests/data/acpi/x86/q35/DSDT.tis.tpm12 | Bin 8961 -> 8995 bytes
tests/data/acpi/x86/q35/DSDT.tis.tpm2 | Bin 8987 -> 9021 bytes
tests/data/acpi/x86/q35/DSDT.type4-count | Bin 18589 -> 18623 bytes
tests/data/acpi/x86/q35/DSDT.viot | Bin 14615 -> 14649 bytes
tests/data/acpi/x86/q35/DSDT.xapic | Bin 35718 -> 35752 bytes
44 files changed, 69 insertions(+), 5 deletions(-)
--
2.34.1
next reply other threads:[~2024-11-03 10:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-03 10:24 Salil Mehta via [this message]
2024-11-03 10:24 ` [PATCH V3 1/5] hw/acpi: Make CPUs ACPI `presence` conditional during vCPU hot-unplug Salil Mehta via
2024-11-03 10:24 ` [PATCH V3 2/5] qtest: allow ACPI DSDT Table changes Salil Mehta via
2024-11-03 10:24 ` [PATCH V3 3/5] hw/acpi: Update ACPI `_STA` method with QOM vCPU ACPI Hotplug states Salil Mehta via
2024-11-03 10:24 ` [PATCH V3 4/5] tests/qtest/bios-tables-test: Update DSDT golden masters for x86/{pc, q35} Salil Mehta via
2024-11-03 10:24 ` [PATCH V3 5/5] hw/acpi: Update GED with vCPU Hotplug VMSD for migration Salil Mehta via
2024-11-04 12:55 ` [PATCH V3 0/5] Arch agnostic ACPI changes to support vCPU Hotplug (on Archs like ARM) Miguel Luis
2024-11-04 15:26 ` Salil Mehta via
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