From: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> In x2apic mode the LDR is fixed based on the ID rather than separately loadable like it was before x2. When kvm_apic_set_state is called, the base is set, and if it has the X2APIC_ENABLE flag set then the LDR is calculated; however that value gets overwritten by the memcpy a few lines below overwriting it with the value that came from userland. The symptom is a lack of EOI after loading the state (e.g. after a QEMU migration) and is due to the EOI bitmap being wrong due to the incorrect LDR. This was seen with a Win2016 guest under Qemu with irqchip=split whose USB mouse didn't work after a VM migration. This corresponds to RH bug: https://bugzilla.redhat.com/show_bug.cgi?id=1502591 Reported-by: Yiqian Wei <yiwei@xxxxxxxxxx> Signed-off-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> --- arch/x86/kvm/lapic.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 4991e9e51611..cff55beb0263 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2201,7 +2201,12 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu, { if (apic_x2apic_mode(vcpu->arch.apic)) { u32 *id = (u32 *)(s->regs + APIC_ID); + u32 *ldr = (u32 *)(s->regs + APIC_LDR); + if (set) { + /* In x2 the LDR is fixed based on the id */ + *ldr = kvm_apic_calc_x2apic_ldr(*id); + } if (vcpu->kvm->arch.x2apic_format) { if (*id != vcpu->vcpu_id) return -EINVAL; -- 2.14.3
