[B][PATCH 1/1] KVM: x86: handle !lapic_in_kernel case in kvm_cpu_*_extint

[Guilherme G. Piccoli]

From: Paolo Bonzini <pbonzini at redhat.com>

BugLink: https://bugs.launchpad.net/bugs/1917138

Centralize handling of interrupts from the userspace APIC
in kvm_cpu_has_extint and kvm_cpu_get_extint, since
userspace APIC interrupts are handled more or less the
same as ExtINTs are with split irqchip.  This removes
duplicated code from kvm_cpu_has_injectable_intr and
kvm_cpu_has_interrupt, and makes the code more similar
between kvm_cpu_has_{extint,interrupt} on one side
and kvm_cpu_get_{extint,interrupt} on the other.

Cc: stable at vger.kernel.org
Reviewed-by: Filippo Sironi <sironi at amazon.de>
Reviewed-by: David Woodhouse <dwmw at amazon.co.uk>
Tested-by: David Woodhouse <dwmw at amazon.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
(backported from commit 72c3bcdcda494cbd600712a32e67702cdee60c07)

[gpiccoli: Besides context adjustments, it's very important to notice
that Ubuntu 4.15 tree lacks the following commit, which renames the
struct member interrupt.pending to interrupt.injected:
04140b4144cd ("KVM: x86: Rename interrupt.pending to interrupt.injected")
This may cause a very confusing comment in kvm_cpu_has_extint(),
hence I've changed both code and comment in order they do make sense.]

Signed-off-by: Guilherme G. Piccoli <gpiccoli at canonical.com>
---
 arch/x86/kvm/irq.c   | 65 ++++++++++++++++++++++++--------------------
 arch/x86/kvm/lapic.c |  2 +-
 2 files changed, 37 insertions(+), 30 deletions(-)

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 8978988e735d..842fcc043a8f 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -54,15 +54,29 @@ static int pending_userspace_extint(struct kvm_vcpu *v)
  */
 int kvm_cpu_has_extint(struct kvm_vcpu *v)
 {
-	u8 accept = kvm_apic_accept_pic_intr(v);
+	/*
+	 * FIXME: interrupt.pending represents an interrupt whose
+	 * side-effects have already been applied (e.g. bit from IRR
+	 * already moved to ISR). Therefore, it is incorrect to rely
+	 * on interrupt.pending to know if there is a pending
+	 * interrupt in the user-mode LAPIC.
+	 * This leads to nVMX/nSVM not be able to distinguish
+	 * if it should exit from L2 to L1 on EXTERNAL_INTERRUPT on
+	 * pending interrupt or should re-inject an injected
+	 * interrupt.
+	 * [backport note: interrupt.pending was renamed interrupt.injected
+	 * in upstream commit 04140b4144cd , not present in this tree.]
+	 */
+	if (!lapic_in_kernel(v))
+		return v->arch.interrupt.pending;
 
-	if (accept) {
-		if (irqchip_split(v->kvm))
-			return pending_userspace_extint(v);
-		else
-			return v->kvm->arch.vpic->output;
-	} else
+	if (!kvm_apic_accept_pic_intr(v))
 		return 0;
+
+	if (irqchip_split(v->kvm))
+		return pending_userspace_extint(v);
+	else
+		return v->kvm->arch.vpic->output;
 }
 
 /*
@@ -73,9 +87,6 @@ int kvm_cpu_has_extint(struct kvm_vcpu *v)
  */
 int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
 {
-	if (!lapic_in_kernel(v))
-		return v->arch.interrupt.pending;
-
 	if (kvm_cpu_has_extint(v))
 		return 1;
 
@@ -91,9 +102,6 @@ int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
  */
 int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
 {
-	if (!lapic_in_kernel(v))
-		return v->arch.interrupt.pending;
-
 	if (kvm_cpu_has_extint(v))
 		return 1;
 
@@ -107,16 +115,21 @@ EXPORT_SYMBOL_GPL(kvm_cpu_has_interrupt);
  */
 static int kvm_cpu_get_extint(struct kvm_vcpu *v)
 {
-	if (kvm_cpu_has_extint(v)) {
-		if (irqchip_split(v->kvm)) {
-			int vector = v->arch.pending_external_vector;
-
-			v->arch.pending_external_vector = -1;
-			return vector;
-		} else
-			return kvm_pic_read_irq(v->kvm); /* PIC */
-	} else
+	if (!kvm_cpu_has_extint(v)) {
+		WARN_ON(!lapic_in_kernel(v));
 		return -1;
+	}
+
+	if (!lapic_in_kernel(v))
+		return v->arch.interrupt.nr;
+
+	if (irqchip_split(v->kvm)) {
+		int vector = v->arch.pending_external_vector;
+
+		v->arch.pending_external_vector = -1;
+		return vector;
+	} else
+		return kvm_pic_read_irq(v->kvm); /* PIC */
 }
 
 /*
@@ -124,13 +137,7 @@ static int kvm_cpu_get_extint(struct kvm_vcpu *v)
  */
 int kvm_cpu_get_interrupt(struct kvm_vcpu *v)
 {
-	int vector;
-
-	if (!lapic_in_kernel(v))
-		return v->arch.interrupt.nr;
-
-	vector = kvm_cpu_get_extint(v);
-
+	int vector = kvm_cpu_get_extint(v);
 	if (vector != -1)
 		return vector;			/* PIC */
 
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e1116584105d..a6084e5750ab 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2217,7 +2217,7 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
 	struct kvm_lapic *apic = vcpu->arch.apic;
 	u32 ppr;
 
-	if (!kvm_apic_hw_enabled(apic))
+	if (!kvm_apic_present(vcpu))
 		return -1;
 
 	__apic_update_ppr(apic, &ppr);
-- 
2.29.0