Guest fails to online hotplugged CPU with error smpboot: do_boot_cpu failed(-1) to wakeup CPU#4 It's caused by the fact that kvm_apic_set_state(), which used to call recalculate_apic_map() unconditionally and pulled hotplugged CPU into apic map, is updating map conditionally [1] on state change which doesn't happen in this case and apic map update is skipped. Note: new CPU during kvm_arch_vcpu_create() is not visible to kvm_recalculate_apic_map(), so all related update calls endup as NOP and only follow up kvm_apic_set_state() used to trigger map update that counted in hotplugged CPU. Fix issue by forcing unconditional update from kvm_apic_set_state(), like it used to be. 1) Fixes: (4abaffce4d25a KVM: LAPIC: Recalculate apic map in batch) Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx> --- PS: it's alternative to full revert of [1], I've posted earlier https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg2205600.html so fii free to pick up whatever is better by now --- arch/x86/kvm/lapic.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 34a7e0533dad..5696831d4005 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2556,6 +2556,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) struct kvm_lapic *apic = vcpu->arch.apic; int r; + apic->vcpu->kvm->arch.apic_map_dirty = true; kvm_lapic_set_base(vcpu, vcpu->arch.apic_base); /* set SPIV separately to get count of SW disabled APICs right */ apic_set_spiv(apic, *((u32 *)(s->regs + APIC_SPIV))); -- 2.26.2
