[PATCH 2/3] KVM: nVMX: Fix fail to get nested ack intr's vector during nested vmexit

[Wanpeng Li <wanpeng.li@linux.intel.com>]

WARNING: CPU: 9 PID: 7251 at arch/x86/kvm/vmx.c:8719 nested_vmx_vmexit+0xa4/0x233 [kvm_intel]()
Modules linked in: tun nfsv3 nfs_acl auth_rpcgss oid_registry nfsv4 dns_resolver nfs fscache lockd
sunrpc pci_stub netconsole kvm_intel kvm bridge stp llc autofs4 8021q ipv6 uinput joydev microcode 
pcspkr igb i2c_algo_bit ehci_pci ehci_hcd e1000e ixgbe ptp pps_core hwmon mdio i2c_i801 i2c_core 
tpm_tis tpm ipmi_si ipmi_msghandler isci libsas scsi_transport_sas button dm_mirror dm_region_hash 
dm_log dm_mod
CPU: 9 PID: 7251 Comm: qemu-system-x86 Tainted: G        W     3.16.0-rc1 #2
Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.00.29.D696.1311111329 11/11/2013
 000000000000220f ffff880ffd107bf8 ffffffff81493563 000000000000220f
 0000000000000000 ffff880ffd107c38 ffffffff8103f0eb ffff880ffd107c48
 ffffffffa059709a ffff881ffc9e0040 ffff8800b74b8000 00000000ffffffff
Call Trace:
 [<ffffffff81493563>] dump_stack+0x49/0x5e
 [<ffffffff8103f0eb>] warn_slowpath_common+0x7c/0x96
 [<ffffffffa059709a>] ? nested_vmx_vmexit+0xa4/0x233 [kvm_intel]
 [<ffffffff8103f11a>] warn_slowpath_null+0x15/0x17
 [<ffffffffa059709a>] nested_vmx_vmexit+0xa4/0x233 [kvm_intel]
 [<ffffffffa0594295>] ? nested_vmx_exit_handled+0x6a/0x39e [kvm_intel]
 [<ffffffffa0537931>] ? kvm_apic_has_interrupt+0x80/0xd5 [kvm]
 [<ffffffffa05972ec>] vmx_check_nested_events+0xc3/0xd3 [kvm_intel]
 [<ffffffffa051ebe9>] inject_pending_event+0xd0/0x16e [kvm]
 [<ffffffffa051efa0>] vcpu_enter_guest+0x319/0x704 [kvm]

After commit 77b0f5d (KVM: nVMX: Ack and write vector info to intr_info if L1 
asks us to), "Acknowledge interrupt on exit" behavior can be emulated. Current
logic will ask for intr vector if it is nested vmexit and VM_EXIT_ACK_INTR_ON_EXIT
is set by L1. However, intr vector for posted intr can't be got by generic read 
pending interrupt vector and intack routine, there is a requirement to sync from 
pir to irr. This patch fix it by ask the intr vector after sync pir to irr.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 arch/x86/kvm/lapic.c | 1 +
 arch/x86/kvm/vmx.c   | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 0069118..b7d45dc 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1637,6 +1637,7 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 	apic_clear_irr(vector, apic);
 	return vector;
 }
+EXPORT_SYMBOL_GPL(kvm_get_apic_interrupt);
 
 void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
 		struct kvm_lapic_state *s)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4ae5ad8..31f1479 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8697,6 +8697,9 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 	if ((exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
 	    && nested_exit_intr_ack_set(vcpu)) {
 		int irq = kvm_cpu_get_interrupt(vcpu);
+
+		if (irq < 0 && kvm_apic_vid_enabled(vcpu->kvm))
+			irq = kvm_get_apic_interrupt(vcpu);
 		WARN_ON(irq < 0);
 		vmcs12->vm_exit_intr_info = irq |
 			INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR;
-- 
1.9.1