6.13-stable review patch. If anyone has any objections, please let me know.
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From: Chao Gao chao.gao@intel.com
commit 04bc93cf49d16d01753b95ddb5d4f230b809a991 upstream.
If KVM emulates an EOI for L1's virtual APIC while L2 is active, defer updating GUEST_INTERUPT_STATUS.SVI, i.e. the VMCS's cache of the highest in-service IRQ, until L1 is active, as vmcs01, not vmcs02, needs to track vISR. The missed SVI update for vmcs01 can result in L1 interrupts being incorrectly blocked, e.g. if there is a pending interrupt with lower priority than the interrupt that was EOI'd.
This bug only affects use cases where L1's vAPIC is effectively passed through to L2, e.g. in a pKVM scenario where L2 is L1's depriveleged host, as KVM will only emulate an EOI for L1's vAPIC if Virtual Interrupt Delivery (VID) is disabled in vmc12, and L1 isn't intercepting L2 accesses to its (virtual) APIC page (or if x2APIC is enabled, the EOI MSR).
WARN() if KVM updates L1's ISR while L2 is active with VID enabled, as an EOI from L2 is supposed to affect L2's vAPIC, but still defer the update, to try to keep L1 alive. Specifically, KVM forwards all APICv-related VM-Exits to L1 via nested_vmx_l1_wants_exit():
case EXIT_REASON_APIC_ACCESS: case EXIT_REASON_APIC_WRITE: case EXIT_REASON_EOI_INDUCED: /* * The controls for "virtualize APIC accesses," "APIC- * register virtualization," and "virtual-interrupt * delivery" only come from vmcs12. */ return true;
Fixes: c7c9c56ca26f ("x86, apicv: add virtual interrupt delivery support") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/kvm/20230312180048.1778187-1-jason.cj.chen@intel.com Reported-by: Markku Ahvenjärvi mankku@gmail.com Closes: https://lore.kernel.org/all/20240920080012.74405-1-mankku@gmail.com Cc: Janne Karhunen janne.karhunen@gmail.com Signed-off-by: Chao Gao chao.gao@intel.com [sean: drop request, handle in VMX, write changelog] Tested-by: Chao Gao chao.gao@intel.com Link: https://lore.kernel.org/r/20241128000010.4051275-3-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/lapic.c | 11 +++++++++++ arch/x86/kvm/lapic.h | 1 + arch/x86/kvm/vmx/nested.c | 5 +++++ arch/x86/kvm/vmx/vmx.c | 21 +++++++++++++++++++++ arch/x86/kvm/vmx/vmx.h | 1 + 5 files changed, 39 insertions(+)
--- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -816,6 +816,17 @@ static inline void apic_clear_isr(int ve } }
+void kvm_apic_update_hwapic_isr(struct kvm_vcpu *vcpu) +{ + struct kvm_lapic *apic = vcpu->arch.apic; + + if (WARN_ON_ONCE(!lapic_in_kernel(vcpu)) || !apic->apicv_active) + return; + + kvm_x86_call(hwapic_isr_update)(vcpu, apic_find_highest_isr(apic)); +} +EXPORT_SYMBOL_GPL(kvm_apic_update_hwapic_isr); + int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu) { /* This may race with setting of irr in __apic_accept_irq() and --- a/arch/x86/kvm/lapic.h +++ b/arch/x86/kvm/lapic.h @@ -118,6 +118,7 @@ void kvm_apic_send_ipi(struct kvm_lapic int kvm_apic_set_base(struct kvm_vcpu *vcpu, u64 value, bool host_initiated); int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s); int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s); +void kvm_apic_update_hwapic_isr(struct kvm_vcpu *vcpu); int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu); --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -5050,6 +5050,11 @@ void nested_vmx_vmexit(struct kvm_vcpu * kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu); }
+ if (vmx->nested.update_vmcs01_hwapic_isr) { + vmx->nested.update_vmcs01_hwapic_isr = false; + kvm_apic_update_hwapic_isr(vcpu); + } + if ((vm_exit_reason != -1) && (enable_shadow_vmcs || nested_vmx_is_evmptr12_valid(vmx))) vmx->nested.need_vmcs12_to_shadow_sync = true; --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6867,6 +6867,27 @@ void vmx_hwapic_isr_update(struct kvm_vc u16 status; u8 old;
+ /* + * If L2 is active, defer the SVI update until vmcs01 is loaded, as SVI + * is only relevant for if and only if Virtual Interrupt Delivery is + * enabled in vmcs12, and if VID is enabled then L2 EOIs affect L2's + * vAPIC, not L1's vAPIC. KVM must update vmcs01 on the next nested + * VM-Exit, otherwise L1 with run with a stale SVI. + */ + if (is_guest_mode(vcpu)) { + /* + * KVM is supposed to forward intercepted L2 EOIs to L1 if VID + * is enabled in vmcs12; as above, the EOIs affect L2's vAPIC. + * Note, userspace can stuff state while L2 is active; assert + * that VID is disabled if and only if the vCPU is in KVM_RUN + * to avoid false positives if userspace is setting APIC state. + */ + WARN_ON_ONCE(vcpu->wants_to_run && + nested_cpu_has_vid(get_vmcs12(vcpu))); + to_vmx(vcpu)->nested.update_vmcs01_hwapic_isr = true; + return; + } + if (max_isr == -1) max_isr = 0;
--- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -176,6 +176,7 @@ struct nested_vmx { bool reload_vmcs01_apic_access_page; bool update_vmcs01_cpu_dirty_logging; bool update_vmcs01_apicv_status; + bool update_vmcs01_hwapic_isr;
/* * Enlightened VMCS has been enabled. It does not mean that L1 has to