From 1c96dcceaeb3a99aaf0d548eef2223e0b02a7e40 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 5 Nov 2020 11:20:49 -0500 Subject: KVM: x86: fix apic_accept_events vs check_nested_events vmx_apic_init_signal_blocked is buggy in that it returns true even in VMX non-root mode. In non-root mode, however, INITs are not latched, they just cause a vmexit. Previously, KVM was waiting for them to be processed when kvm_apic_accept_events and in the meanwhile it ate the SIPIs that the processor received. However, in order to implement the wait-for-SIPI activity state, KVM will have to process KVM_APIC_SIPI in vmx_check_nested_events, and it will not be possible anymore to disregard SIPIs in non-root mode as the code is currently doing. By calling kvm_x86_ops.nested_ops->check_events, we can force a vmexit (with the side-effect of latching INITs) before incorrectly injecting an INIT or SIPI in a guest, and therefore vmx_apic_init_signal_blocked can do the right thing. Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 30 ++++++++++++++++++++++++++---- arch/x86/kvm/vmx/vmx.c | 2 +- 2 files changed, 27 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 105e7859d1f2..e3ee597ff540 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2843,14 +2843,35 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu) { struct kvm_lapic *apic = vcpu->arch.apic; u8 sipi_vector; + int r; unsigned long pe; - if (!lapic_in_kernel(vcpu) || !apic->pending_events) + if (!lapic_in_kernel(vcpu)) + return; + + /* + * Read pending events before calling the check_events + * callback. + */ + pe = smp_load_acquire(&apic->pending_events); + if (!pe) return; + if (is_guest_mode(vcpu)) { + r = kvm_x86_ops.nested_ops->check_events(vcpu); + if (r < 0) + return; + /* + * If an event has happened and caused a vmexit, + * we know INITs are latched and therefore + * we will not incorrectly deliver an APIC + * event instead of a vmexit. + */ + } + /* * INITs are latched while CPU is in specific states - * (SMM, VMX non-root mode, SVM with GIF=0). + * (SMM, VMX root mode, SVM with GIF=0). * Because a CPU cannot be in these states immediately * after it has processed an INIT signal (and thus in * KVM_MP_STATE_INIT_RECEIVED state), just eat SIPIs @@ -2858,13 +2879,13 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu) */ if (kvm_vcpu_latch_init(vcpu)) { WARN_ON_ONCE(vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED); - if (test_bit(KVM_APIC_SIPI, &apic->pending_events)) + if (test_bit(KVM_APIC_SIPI, &pe)) clear_bit(KVM_APIC_SIPI, &apic->pending_events); return; } - pe = xchg(&apic->pending_events, 0); if (test_bit(KVM_APIC_INIT, &pe)) { + clear_bit(KVM_APIC_INIT, &apic->pending_events); kvm_vcpu_reset(vcpu, true); if (kvm_vcpu_is_bsp(apic->vcpu)) vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE; @@ -2873,6 +2894,7 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu) } if (test_bit(KVM_APIC_SIPI, &pe) && vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) { + clear_bit(KVM_APIC_SIPI, &apic->pending_events); /* evaluate pending_events before reading the vector */ smp_rmb(); sipi_vector = apic->sipi_vector; diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 39ff7600b0af..fd70bdf63844 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7558,7 +7558,7 @@ static void enable_smi_window(struct kvm_vcpu *vcpu) static bool vmx_apic_init_signal_blocked(struct kvm_vcpu *vcpu) { - return to_vmx(vcpu)->nested.vmxon; + return to_vmx(vcpu)->nested.vmxon && !is_guest_mode(vcpu); } static void vmx_migrate_timers(struct kvm_vcpu *vcpu) -- cgit v1.2.3