From 0bcc3fb95b97ac2ca223a5a870287b37f56265ac Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Fri, 9 Feb 2018 14:01:33 +0100 Subject: [PATCH] KVM: lapic: stop advertising DIRECTED_EOI when in-kernel IOAPIC is in use MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Radim Krčmář --- 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 391dda8d43b7..70dcb5548022 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); }