FAILED: patch "[PATCH] KVM: nVMX: Morph notification vector IRQ on nested VM-Enter" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 25bb2cf97139f81e3bb8910d26016a529019528e Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
Date: Wed, 12 Aug 2020 10:51:29 -0700
Subject: [PATCH] KVM: nVMX: Morph notification vector IRQ on nested VM-Enter
to pending PI

On successful nested VM-Enter, check for pending interrupts and convert the highest priority interrupt to a pending posted interrupt if it matches L2's notification vector. If the vCPU receives a notification interrupt before nested VM-Enter (assuming L1 disables IRQs before doing VM-Enter), the pending interrupt (for L1) should be recognized and processed as a posted interrupt when interrupts become unblocked after VM-Enter to L2.

This fixes a bug where L1/L2 will get stuck in an infinite loop if L1 is trying to inject an interrupt into L2 by setting the appropriate bit in L2's PIR and sending a self-IPI prior to VM-Enter (as opposed to KVM's method of manually moving the vector from PIR->vIRR/RVI). KVM will observe the IPI while the vCPU is in L1 context and so won't immediately morph it to a posted interrupt for L2. The pending interrupt will be seen by vmx_check_nested_events(), cause KVM to force an immediate exit after nested VM-Enter, and eventually be reflected to L1 as a VM-Exit. After handling the VM-Exit, L1 will see that L2 has a pending interrupt in PIR, send another IPI, and repeat until L2 is killed.

Note, posted interrupts require virtual interrupt deliveriy, and virtual interrupt delivery requires exit-on-interrupt, ergo interrupts will be unconditionally unmasked on VM-Enter if posted interrupts are enabled.

Message-Id: <[email protected]>

index 51ed4f0b1390..105e7859d1f2 100644
@@ -494,6 +494,12 @@ static inline void apic_clear_irr(int vec, struct kvm_lapic *apic)
 	}
 }
 
+void kvm_apic_clear_irr(struct kvm_vcpu *vcpu, int vec)
+{
+	apic_clear_irr(vec, vcpu->arch.apic);
+}
+EXPORT_SYMBOL_GPL(kvm_apic_clear_irr);
+
 static inline void apic_set_isr(int vec, struct kvm_lapic *apic)
 {
 	struct kvm_vcpu *vcpu;

@@ -2465,6 +2471,7 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
 	__apic_update_ppr(apic, &ppr);
 	return apic_has_interrupt_for_ppr(apic, ppr);
 }
+EXPORT_SYMBOL_GPL(kvm_apic_has_interrupt);
 
 int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu)
 {

index 754f29beb83e..4fb86e3a9dd3 100644
@@ -89,6 +89,7 @@ int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
 bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
 			   int shorthand, unsigned int dest, int dest_mode);
 int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2);
+void kvm_apic_clear_irr(struct kvm_vcpu *vcpu, int vec);
 bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr);
 bool kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir, int *max_irr);
 void kvm_apic_update_ppr(struct kvm_vcpu *vcpu);

index 9861179d9a8c..f39491cc92c7 100644
@@ -3531,6 +3531,14 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	if (unlikely(status != NVMX_VMENTRY_SUCCESS))
 		goto vmentry_failed;
 
+	/* Emulate processing of posted interrupts on VM-Enter. */
+	if (nested_cpu_has_posted_intr(vmcs12) &&
+	    kvm_apic_has_interrupt(vcpu) == vmx->nested.posted_intr_nv) {
+		vmx->nested.pi_pending = true;
+		kvm_make_request(KVM_REQ_EVENT, vcpu);
+		kvm_apic_clear_irr(vcpu, vmx->nested.posted_intr_nv);
+	}
+
 	/* Hide L1D cache contents from the nested guest.  */
 	vmx->vcpu.arch.l1tf_flush_l1d = true;