On 21/05/2017 05:32, Wanpeng Li wrote: > vmx_cancel_hv_timer > vCPU0's vmx->hv_deadline_tsc = -1 > > preempt occur > > clear preemption timer field in CPU1's > active vmcs > vCPU0's apic_timer.hv_timer_in_use = > false > vmx_vcpu_run(vCPU0) > vmx_arm_hv_timer > if (vmx->hv_deadline_tsc == -1) > nothing change > > handle_preemption_timer(vCPU0) > kvm_lapic_expired_hv_timer > WARN_ON(!apic->lapic_timer.hv_timer_in_use); > > Preemption can occur during cancel preemption timer, and there will be > inconsistent > status in lapic, vmx and vmcs field. This patch fixes it by disable > preemption for > cancelling preemption timer.
I see, so the purpose is to serialize against kvm_arch_vcpu_load. Nice catch, I've queued the patch for kvm/master. Paolo > Cc: Paolo Bonzini <[email protected]> > Cc: Radim Krčmář <[email protected]> > Signed-off-by: Wanpeng Li <[email protected]> > --- > arch/x86/kvm/lapic.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index c329d28..6e6f345 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1495,8 +1495,10 @@ EXPORT_SYMBOL_GPL(kvm_lapic_hv_timer_in_use); > > static void cancel_hv_timer(struct kvm_lapic *apic) > { > + preempt_disable(); > kvm_x86_ops->cancel_hv_timer(apic->vcpu); > apic->lapic_timer.hv_timer_in_use = false; > + preempt_enable(); > } > > static bool start_hv_timer(struct kvm_lapic *apic) > --
