docs: add CPU and memory hotplug how-to for virtual machines#979
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Verified live on CentOS 7.9 / Ubuntu 20.04 / Debian 13 guests: hotplug is delivered via automatic live migration; CPU auto-online is RHEL-only; memory hotplug (virtio-mem) needs guest kernel 5.16+ (QEMU requires UNPLUGGED_INACCESSIBLE), pending requests apply on next restart; reductions set RestartRequired. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…plug VMs sized via resources.requests/limits (the web console form) lack the cpu/memory spec fields; adding them is a non-live-updatable change that sets RestartRequired. Verified live. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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CPU hotplug: hot-added vCPUs are used immediately (verified on Standard edition, live session). Memory hotplug: no Windows virtio-mem driver exists — the device sits in Device Manager with a driver error and the request stays pending until a cold restart. Also document cancelling a pending memory request by reverting memory.guest. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…iomem, per-resource first resize All six review findings verified against the shipped KubeVirt v1.8.4 source and re-tested on a live cluster before rewriting: - Memory CAN be scaled down live as long as the target stays >= guestAtBoot (verified Debian 13 4Gi->3Gi and Windows 10Gi->9Gi->8Gi online); only going below the boot value sets RestartRequired. CPU reduction still always does. - Windows memory hotplug WORKS once the viomem driver from the platform's virtio-win ISO (0.1.266 ships viomem for 2k16-2k25) is installed — verified live 8Gi->10Gi with pnputil-installed driver. Rewrote the 'no Windows driver' claim and added install instructions. - First resize of a console-created (resources-only) VM: adding memory.guest alone is live; only adding the cpu block needs one restart — and a combined patch suppresses the live memory path too (all three cases verified). - maxSockets/maxGuest are auto-computed at VMI start when omitted; reworded the contradictory 'must declare before start' prerequisite. - Replaced the bare 'kernel 5.16+' rule with feature-negotiation guidance: distro kernels backport independently (RHEL 9.4+/8.10 work; Ubuntu 22.04 GA 5.15 does NOT — corrected the previous 22.04+ recommendation). - RWX prerequisite scoped to PVC/DataVolume-backed disks with LiveMigratable as the real gate; dmesg troubleshooting no longer equates 'no output' with 'kernel too old'. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_018wp7GTjNPrAwPJpzmHNgn5
…st policy, scope claims to tested guests - Memory scale-down reworded as a best-effort request: accepted live (no RestartRequired at >= guestAtBoot) but completion depends on the guest freeing the memory. Verified live: under artificial memory pressure a Debian 13 shrink stalled at ~2.1Gi of a 2Gi request with no error, and ~86Mi stayed unreclaimable even after the pressure was removed. - Debian's automatic memory onlining attributed to the image's kernel policy (auto_online_blocks=online, verified in-guest), not to the virtio-mem driver; added the check command. - Troubleshooting split by direction: guestRequested>guestCurrent (driver/ feature/onlining) vs guestRequested<guestCurrent (unmovable/locked pages, may never fully complete, not an error). - CPU guidance scoped to the four tested guests; Windows limited to Windows Server 2022 with a note that CPU hot-add depends on dynamic-hardware-partitioning support in specific SKUs. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_018wp7GTjNPrAwPJpzmHNgn5
…r states, verified-vs-documented scope Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_018wp7GTjNPrAwPJpzmHNgn5
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Summary
Adds a how-to under
virtualization/virtual_machine/how_to/covering CPU and memory hotplug for running VMs, based on live verification on an ACP 4.4 test cluster (HCO v4.4.3 / KubeVirt v1.8.4) with CentOS 7.9, Ubuntu 20.04, Debian 13, and Windows Server 2022 guests. Two review rounds have been incorporated; every corrected statement was re-verified against the shipped KubeVirt v1.8.4 source and/or live tests.Key verified findings documented:
LiveMigratable=True— RWX is required for PVC/DataVolume-backed disks only.maxSockets/maxGuestare auto-computed at VMI start when omitted (default 4×, configurable); explicit values remain recommended.UNPLUGGED_INACCESSIBLEfeature — upstream kernel 5.16+, but distributions backport independently (RHEL 9.4+ and 8.10 work — though 8.10 is hot-plug only by default; Ubuntu 22.04 GA 5.15 does not). Windows Server 2022 works once theviomemdriver from the platform's virtio-win ISO (0.1.266) is installed — verified live 8Gi→10Gi online; without it the request stays silently pending and applies cold on the next restart.RestartRequired.memory.guestalone is applied live; the first addition of acpublock requires one restart, and a combined patch suppresses the live memory path too.Validation
yarn lint— 0 errors / 0 warningsyarn build— passed🤖 Generated with Claude Code
https://claude.ai/code/session_018wp7GTjNPrAwPJpzmHNgn5