| From foo@baz Sun May 27 17:33:38 CEST 2018 |
| From: Vitaly Kuznetsov <vkuznets@redhat.com> |
| Date: Fri, 9 Feb 2018 14:01:33 +0100 |
| Subject: KVM: lapic: stop advertising DIRECTED_EOI when in-kernel IOAPIC is in use |
| |
| From: Vitaly Kuznetsov <vkuznets@redhat.com> |
| |
| [ 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> |
| --- |
| arch/x86/kvm/lapic.c | 10 +++++++++- |
| 1 file changed, 9 insertions(+), 1 deletion(-) |
| |
| --- a/arch/x86/kvm/lapic.c |
| +++ b/arch/x86/kvm/lapic.c |
| @@ -299,8 +299,16 @@ void kvm_apic_set_version(struct kvm_vcp |
| 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); |
| } |
