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KVM: lapic: stop advertising DIRECTED_EOI when in-kernel IOAPIC is in use 

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 <vkuznets@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2018-02-09 14:01:33 +01:00 committed by Paolo Bonzini
parent c51eb52b8f
commit 0bcc3fb95b
1 changed files with 9 additions and 1 deletions
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10
arch/x86/kvm/lapic.c
View File

@ -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);
}