Devices which use level-triggered interrupts under Windows 2016 with Hyper-V role enabled don't work: Windows disables EOI broadcast in SPIV unconditionally. Our in-kernel IOAPIC implementation emulates an old IOAPIC version which has no EOI register so EOI never happens.
The issue was discovered and discussed a while ago: https://www.spinics.net/lists/kvm/msg148098.html While this is a guest OS bug (it should check that IOAPIC has the required capabilities before disabling EOI broadcast) we can workaround it in KVM: advertising DIRECTED_EOI with in-kernel IOAPIC makes little sense anyway. Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com> --- - Radim's suggestion was to disable DIRECTED_EOI unconditionally but I'm not that radical :-) In theory, we may have multiple IOAPICs in userspace in future and DIRECTED_EOI can be leveraged. --- arch/x86/kvm/lapic.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 924ac8ce9d50..5339287fee63 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -321,8 +321,16 @@ void kvm_apic_set_version(struct kvm_vcpu *vcpu) if (!lapic_in_kernel(vcpu)) return; + /* + * KVM emulates 82093AA datasheet (with in-kernel IOAPIC implementation) + * which doesn't have EOI register; Some buggy OSes (e.g. Windows with + * Hyper-V role) disable EOI broadcast in lapic not checking for IOAPIC + * version first and level-triggered interrupts never get EOIed in + * IOAPIC. + */ feat = kvm_find_cpuid_entry(apic->vcpu, 0x1, 0); - if (feat && (feat->ecx & (1 << (X86_FEATURE_X2APIC & 31)))) + if (feat && (feat->ecx & (1 << (X86_FEATURE_X2APIC & 31))) && + !ioapic_in_kernel(vcpu->kvm)) v |= APIC_LVR_DIRECTED_EOI; kvm_lapic_set_reg(apic, APIC_LVR, v); } -- 2.14.3