vmcs->cpu indicates whether it exists on the target cpu, -1 means the vmcs does not exist on any vcpu If vcpu load vmcs with vmcs.cpu = -1, it can be directly added to cpu's percpu list. The list can be corrupted if the cpu prefetch the vmcs's list before reading vmcs->cpu. Meanwhile, we should remove vmcs from the list before making vmcs->vcpu == -1 be visible Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/vmx.c | 17 +++++++++++++++++ 1 files changed, 17 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 29e8f42..6056d88 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1002,6 +1002,15 @@ static void __loaded_vmcs_clear(void *arg) if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs) per_cpu(current_vmcs, cpu) = NULL; list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link); + + /* + * we should ensure updating loaded_vmcs->loaded_vmcss_on_cpu_link + * is before setting loaded_vmcs->vcpu to -1 which is done in + * loaded_vmcs_init. Otherwise, other cpu can see vcpu = -1 fist + * then adds the vmcs into percpu list before it is deleted. + */ + smp_wmb(); + loaded_vmcs_init(loaded_vmcs); } @@ -1537,6 +1546,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); local_irq_disable(); + + /* + * Read loaded_vmcs->cpu should be before fetching + * loaded_vmcs->loaded_vmcss_on_cpu_link. + * See the comments in __loaded_vmcs_clear(). + */ + smp_rmb(); + list_add(&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link, &per_cpu(loaded_vmcss_on_cpu, cpu)); local_irq_enable(); -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
