linux-kernel - [PATCH 1/2] KVM: LAPIC: Don't silently accept bad vectors

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Date:   Tue, 26 Sep 2017 23:34:21 -0700
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: [PATCH 1/2] KVM: LAPIC: Don't silently accept bad vectors

From: Wanpeng Li <wanpeng.li@...mail.com>

Vectors 0-15 are reserved, and a physical LAPIC - upon sending or
receiving one - would generate an APIC error instead of doing the
requested action. Make our emulation behave similarly.

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
---
 arch/x86/kvm/lapic.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 6bafd06..a779ba9 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -935,6 +935,25 @@ bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
 	return ret;
 }
 
+static void apic_error(struct kvm_lapic *apic, unsigned long errmask)
+{
+	uint32_t esr;
+
+	esr = kvm_lapic_get_reg(apic, APIC_ESR);
+
+	if ((esr & errmask) != errmask) {
+		uint32_t lvterr = kvm_lapic_get_reg(apic, APIC_LVTERR);
+
+		kvm_lapic_set_reg(apic, APIC_ESR, esr | errmask);
+		if (!(lvterr & APIC_LVT_MASKED)) {
+			struct kvm_lapic_irq irq;
+
+			irq.vector = lvterr & 0xff;
+			kvm_irq_delivery_to_apic(apic->vcpu->kvm, apic, &irq, NULL);
+		}
+	}
+}
+
 /*
  * Add a pending IRQ into lapic.
  * Return 1 if successfully added and 0 if discarded.
@@ -946,6 +965,11 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
 	int result = 0;
 	struct kvm_vcpu *vcpu = apic->vcpu;
 
+	if (unlikely(vector < 16) && delivery_mode == APIC_DM_FIXED) {
+		apic_error(apic, APIC_ESR_RECVILL);
+		return 0;
+	}
+
 	trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode,
 				  trig_mode, vector);
 	switch (delivery_mode) {
@@ -1146,7 +1170,10 @@ static void apic_send_ipi(struct kvm_lapic *apic)
 		   irq.trig_mode, irq.level, irq.dest_mode, irq.delivery_mode,
 		   irq.vector, irq.msi_redir_hint);
 
-	kvm_irq_delivery_to_apic(apic->vcpu->kvm, apic, &irq, NULL);
+	if (unlikely(irq.vector < 16 && irq.delivery_mode == APIC_DM_FIXED))
+		apic_error(apic, APIC_ESR_SENDILL);
+	else
+		kvm_irq_delivery_to_apic(apic->vcpu->kvm, apic, &irq, NULL);
 }
 
 static u32 apic_get_tmcct(struct kvm_lapic *apic)
@@ -1734,7 +1761,6 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 	case APIC_LVTPC:
 	case APIC_LVT1:
 	case APIC_LVTERR:
-		/* TODO: Check vector */
 		if (!kvm_apic_sw_enabled(apic))
 			val |= APIC_LVT_MASKED;
 
-- 
2.7.4