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Commit e1d32f93 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Greg Kroah-Hartman
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KVM: lapic: stop advertising DIRECTED_EOI when in-kernel IOAPIC is in use 

[ Upstream commit 0bcc3fb95b97ac2ca223a5a870287b37f56265ac ]

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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f5941812

arch/x86/kvm/lapic.c

+9 −1
Original line number Diff line number Diff line
@@ -299,8 +299,16 @@ 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);

}