KVM: x86: Fix virtual wire mode

Intel SDM says, that at most one LAPIC should be configured with ExtINT
delivery. KVM configures all LAPICs this way. This causes pic_unlock()
to kick the first available vCPU from the internal KVM data structures.
If this vCPU is not the BSP, but some not-yet-booted AP, the BSP may
never realize that there is an interrupt.

Fix that by enabling ExtINT delivery only for the BSP.

This allows booting a Linux guest without a TSC in the above situation.
Otherwise the BSP gets stuck in calibrate_delay_converge().

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 6e6f345adfe6a3bf777225b996d0d3aeb1cec51a..d24c8742d9b0aa6df35d5e479e627ff008ea221f 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1936,7 +1936,8 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
        for (i = 0; i < KVM_APIC_LVT_NUM; i++)
                kvm_lapic_set_reg(apic, APIC_LVTT + 0x10 * i, APIC_LVT_MASKED);
        apic_update_lvtt(apic);
-       if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_LINT0_REENABLED))
+       if (kvm_vcpu_is_reset_bsp(vcpu) &&
+           kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_LINT0_REENABLED))
                kvm_lapic_set_reg(apic, APIC_LVT0,
                             SET_APIC_DELIVERY_MODE(0, APIC_MODE_EXTINT));
        apic_manage_nmi_watchdog(apic, kvm_lapic_get_reg(apic, APIC_LVT0));