[PATCH v2 6.1.y 2/3] KVM: nVMX: Check for pending posted interrupts when looking for nested events

[Nicholas Dudar]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

commit 27c4fa42b11af780d49ce704f7fa67b3c2544df4 upstream.

Check for pending (and notified!) posted interrupts when checking if L2
has a pending wake event, as fully posted/notified virtual interrupt is a
valid wake event for HLT.

Note that KVM must check vmx->nested.pi_pending to avoid prematurely
waking L2, e.g. even if KVM sees a non-zero PID.PIR and PID.0N=1, the
virtual interrupt won't actually be recognized until a notification IRQ is
received by the vCPU or the vCPU does (nested) VM-Enter.

Fixes: 26844fee6ade ("KVM: x86: never write to memory from kvm_vcpu_check_block()")
Cc: stable@xxxxxxxxxxxxxxx
Cc: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Reported-by: Jim Mattson <jmattson@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/20231207010302.2240506-1-jmattson@xxxxxxxxxx
Link: https://lore.kernel.org/r/20240607172609.3205077-5-seanjc@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
[ Nicholas Dudar: backport to 6.1.y. Prerequisite for the next patch, which
  folds its check into the vmx_has_nested_events() body this patch builds.
  Applies cleanly. The for_injection path still returns preemption_timer ||
  mtf, as the previous 6.1.y body did. ]
Signed-off-by: Nicholas Dudar <main.kalliope@xxxxxxxxx>
---
 arch/x86/kvm/vmx/nested.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 7d8e18dbe..ad07e83d2 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3953,8 +3953,40 @@ static bool nested_vmx_preemption_timer_pending(struct kvm_vcpu *vcpu)
 
 static bool vmx_has_nested_events(struct kvm_vcpu *vcpu, bool for_injection)
 {
-	return nested_vmx_preemption_timer_pending(vcpu) ||
-	       to_vmx(vcpu)->nested.mtf_pending;
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	void *vapic = vmx->nested.virtual_apic_map.hva;
+	int max_irr, vppr;
+
+	if (nested_vmx_preemption_timer_pending(vcpu) ||
+	    vmx->nested.mtf_pending)
+		return true;
+
+	/*
+	 * Virtual Interrupt Delivery doesn't require manual injection.  Either
+	 * the interrupt is already in GUEST_RVI and will be recognized by CPU
+	 * at VM-Entry, or there is a KVM_REQ_EVENT pending and KVM will move
+	 * the interrupt from the PIR to RVI prior to entering the guest.
+	 */
+	if (for_injection)
+		return false;
+
+	if (!nested_cpu_has_vid(get_vmcs12(vcpu)) ||
+	    __vmx_interrupt_blocked(vcpu))
+		return false;
+
+	if (!vapic)
+		return false;
+
+	vppr = *((u32 *)(vapic + APIC_PROCPRI));
+
+	if (vmx->nested.pi_pending && vmx->nested.pi_desc &&
+	    pi_test_on(vmx->nested.pi_desc)) {
+		max_irr = pi_find_highest_vector(vmx->nested.pi_desc);
+		if (max_irr > 0 && (max_irr & 0xf0) > (vppr & 0xf0))
+			return true;
+	}
+
+	return false;
 }
 
 /*
-- 
2.34.1