release/5.2.37/KVM-VMX-Consider-PID.PIR-to-determine-if-vCPU-has-pe.patch

From efb4e067450ad88970b392bffd09879a8db9a5fa Mon Sep 17 00:00:00 2001
From: Joao Martins <joao.m.martins@oracle.com>
Date: Mon, 11 Nov 2019 17:20:10 +0000
Subject: [PATCH] KVM: VMX: Consider PID.PIR to determine if vCPU has pending
 interrupts

commit 9482ae458b7ae1b47c76333592bbe013d47e579f upstream.

Commit 17e433b54393 ("KVM: Fix leak vCPU's VMCS value into other pCPU")
introduced vmx_dy_apicv_has_pending_interrupt() in order to determine
if a vCPU have a pending posted interrupt. This routine is used by
kvm_vcpu_on_spin() when searching for a a new runnable vCPU to schedule
on pCPU instead of a vCPU doing busy loop.

vmx_dy_apicv_has_pending_interrupt() determines if a
vCPU has a pending posted interrupt solely based on PID.ON. However,
when a vCPU is preempted, vmx_vcpu_pi_put() sets PID.SN which cause
raised posted interrupts to only set bit in PID.PIR without setting
PID.ON (and without sending notification vector), as depicted in VT-d
manual section 5.2.3 "Interrupt-Posting Hardware Operation".

Therefore, checking PID.ON is insufficient to determine if a vCPU has
pending posted interrupts and instead we should also check if there is
some bit set on PID.PIR if PID.SN=1.

Fixes: 17e433b54393 ("KVM: Fix leak vCPU's VMCS value into other pCPU")
Reviewed-by: Jagannathan Raman <jag.raman@oracle.com>
Co-developed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d3c8a2d9cfcf..a879f3b65df4 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6092,7 +6092,11 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
 
 static bool vmx_dy_apicv_has_pending_interrupt(struct kvm_vcpu *vcpu)
 {
-	return pi_test_on(vcpu_to_pi_desc(vcpu));
+	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+
+	return pi_test_on(pi_desc) ||
+		(pi_test_sn(pi_desc) &&
+		!bitmap_empty((unsigned long *)pi_desc->pir, NR_VECTORS));
 }
 
 static void vmx_load_eoi_exitmap(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)
-- 
2.7.4