On Tue, Aug 30, 2022 at 05:01:20AM -0700, isaku.yamahata@xxxxxxxxx wrote: >From: Chao Gao <chao.gao@xxxxxxxxx> > >The CPU STARTING section doesn't allow callbacks to fail. Move KVM's >hotplug callback to ONLINE section so that it can abort onlining a CPU in >certain cases to avoid potentially breaking VMs running on existing CPUs. >For example, when kvm fails to enable hardware virtualization on the >hotplugged CPU. > >Place KVM's hotplug state before CPUHP_AP_SCHED_WAIT_EMPTY as it ensures >when offlining a CPU, all user tasks and non-pinned kernel tasks have left >the CPU, i.e. there cannot be a vCPU task around. So, it is safe for KVM's >CPU offline callback to disable hardware virtualization at that point. >Likewise, KVM's online callback can enable hardware virtualization before >any vCPU task gets a chance to run on hotplugged CPUs. > >KVM's CPU hotplug callbacks are renamed as well. > >Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx> Isaku, your signed-off-by is missing. >Link: https://lore.kernel.org/r/20220216031528.92558-6-chao.gao@xxxxxxxxx >--- > include/linux/cpuhotplug.h | 2 +- > virt/kvm/kvm_main.c | 30 ++++++++++++++++++++++-------- > 2 files changed, 23 insertions(+), 9 deletions(-) > >diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h >index f61447913db9..7972bd63e0cb 100644 >--- a/include/linux/cpuhotplug.h >+++ b/include/linux/cpuhotplug.h >@@ -185,7 +185,6 @@ enum cpuhp_state { > CPUHP_AP_CSKY_TIMER_STARTING, > CPUHP_AP_TI_GP_TIMER_STARTING, > CPUHP_AP_HYPERV_TIMER_STARTING, >- CPUHP_AP_KVM_STARTING, > CPUHP_AP_KVM_ARM_VGIC_INIT_STARTING, > CPUHP_AP_KVM_ARM_VGIC_STARTING, > CPUHP_AP_KVM_ARM_TIMER_STARTING, The movement of CPUHP_AP_KVM_STARTING changes the ordering between CPUHP_AP_KVM_STARTING and CPUHP_AP_KVM_ARM_* above [1]. We need the patch [2] from Marc to avoid breaking ARM. [1] https://lore.kernel.org/lkml/87sfsq4xy8.wl-maz@xxxxxxxxxx/ [2] https://lore.kernel.org/lkml/20220216031528.92558-5-chao.gao@xxxxxxxxx/
