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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: UT90I6fjRJc/0nnYOjgXPQ4MsxyuhtEUy2F7aQSye4Bs8ISzXSZQAKxHvDB/Xo2BaZoHSC1fh0G79GPB9HAKG8diflv/63P47Yl1llC14eiZ+Atjq93Snw0wiob/Ccna9G8RMHOhEnBb2Lil7L/mTR9pkqFCkrK1/ptbMcjqgL34qq0V2ZMZJIYBwXM0eBpTAyHRyzUHj51LmWgmBXkd+erb1x+ODu0lz6wpmFRhrDaEYVWs2Jynhr8onsHTiofQ8jnQ4/8tTak0YNM98TV03cSMfOnLv1rRCCQQVE+3ioLtuIsTxNALCVyHCNvaLu+u1N6PjJTJHoxOMYQPW6wy6paNbpv5Hc3NY/HsnKAfONciMvyhPw/7tVDIonRUhe9/ucdaG2Csvlkf+yb5MEDKjN8ghF//uz4Ocmv/+r9q+cZL9V15Jkv1MKvn7ugDoIFT X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Feb 2026 16:36:13.0247 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8b0703e7-dc5f-4e69-8584-08de63425826 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AMS1EPF00000043.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: GVXPR08MB10812 Hi Mykyta, > On 13 Jan 2026, at 09:45, Mykyta Poturai wrote: >=20 > This series implements support for CPU hotplug/unplug on Arm. To achieve = this, > several things need to be done: >=20 > 1. XEN_SYSCTL_CPU_HOTPLUG_* calls implemented on Arm64. > 2. Enabled building of xen-hptool. > 3. Migration of irqs from dying CPUs implemented. >=20 > Tested on QEMU. Do you have a way to validate this on real hardware ? Doing hotplug/unplug might have side effects (caches, coherency, interrupts= , etc) that I would not be completely confident to have validated by only testing this = in qemu. Could you explain how you validated this (what kind of tests you did). I would be interested to know how the system behave in the following cases: - stopping cpu with guests pinned to specific cores - stopping a cpu with a guest pinned and only running on that one - checking with passthrough devices (for irq balancing) Then a general remark i have is that most of this code (if not all) is alwa= ys in Xen even if CONFIG_CPU_HOTPLUG is not activated in xen config which will probab= ly generate some dead code. Could we protect some of the code not used when HOTPLUG is not activated with if (is_enabled(CONFIG_CPU_HOTPLUG)) or equivalent forms ? Cheers Bertrand >=20 > v4->v5: > * drop merged patches > * combine "smp: Move cpu_up/down helpers to common code" with=20 > "arm/sysctl: Implement cpu hotplug ops" > * see individual patches >=20 > v3->v4: > * add irq migration patches > * see individual patches >=20 > v2->v3: > * add docs >=20 > v1->v2: > * see individual patches >=20 > Mykyta Poturai (5): > arm/irq: Keep track of irq affinities > arm/irq: Migrate IRQs during CPU up/down operations > arm/sysctl: Implement cpu hotplug ops > tools: Allow building xen-hptool without CONFIG_MIGRATE > docs: Document CPU hotplug >=20 > SUPPORT.md | 1 + > docs/misc/cpu-hotplug.txt | 50 +++++++++++++++++++++++++ > tools/libs/guest/Makefile.common | 2 +- > tools/misc/Makefile | 2 +- > xen/arch/arm/Kconfig | 1 + > xen/arch/arm/gic-vgic.c | 2 + > xen/arch/arm/include/asm/irq.h | 2 + > xen/arch/arm/irq.c | 63 +++++++++++++++++++++++++++++++- > xen/arch/arm/smp.c | 9 +++++ > xen/arch/arm/smpboot.c | 6 +++ > xen/arch/arm/vgic.c | 14 ++++++- > xen/arch/ppc/stubs.c | 4 ++ > xen/arch/riscv/stubs.c | 5 +++ > xen/arch/x86/Kconfig | 1 + > xen/arch/x86/include/asm/smp.h | 3 -- > xen/arch/x86/smp.c | 33 ++--------------- > xen/arch/x86/sysctl.c | 12 ++---- > xen/common/Kconfig | 3 ++ > xen/common/smp.c | 34 +++++++++++++++++ > xen/common/sysctl.c | 45 +++++++++++++++++++++++ > xen/include/xen/smp.h | 4 ++ > 21 files changed, 248 insertions(+), 48 deletions(-) > create mode 100644 docs/misc/cpu-hotplug.txt >=20 > --=20 > 2.51.2