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authorVitaly Kuznetsov <vkuznets@redhat.com>2018-02-09 14:01:33 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-30 07:52:31 +0200
commit25b69a422b592edd2739fab9150f5d29955043f7 (patch)
tree00bb48180e474f9f22903efc2de28d683453ebfb /arch
parent982f8f14e704ad07e4093e208723157312620b27 (diff)
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: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/lapic.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 6942d495e897..6d0fbff71d7a 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);
}