Messages in this thread Patch in this message | | | Date | Mon, 14 Nov 2022 13:20:55 -0700 | From | Greg Edwards <> | Subject | [PATCH] KVM: x86: Allow APICv APIC ID inhibit to be cleared on legacy kernels |
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Legacy kernels prior to commit 4399c03c6780 ("x86/apic: Remove verify_local_APIC()") write the xAPIC ID of the boot CPU twice to verify a functioning local APIC. This results in APIC acceleration inhibited on these kernels for reason APICV_INHIBIT_REASON_APIC_ID_MODIFIED.
Allow the APICV_INHIBIT_REASON_APIC_ID_MODIFIED inhibit reason to be cleared if/when the xAPIC ID is set back to the expected vcpu_id value. This occurs on the second xAPIC ID write in verify_local_APIC().
Fixes: 3743c2f02517 ("KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base") Signed-off-by: Greg Edwards <gedwards@ddn.com> --- arch/x86/kvm/lapic.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index d7639d126e6c..4064d0af094d 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2075,8 +2075,13 @@ static void kvm_lapic_xapic_id_updated(struct kvm_lapic *apic) if (KVM_BUG_ON(apic_x2apic_mode(apic), kvm)) return; - if (kvm_xapic_id(apic) == apic->vcpu->vcpu_id) + if (kvm_xapic_id(apic) == apic->vcpu->vcpu_id) { + /* Legacy kernels prior to 4399c03c6780 write APIC ID twice. */ + if (!kvm_apicv_activated(kvm)) + kvm_clear_apicv_inhibit(kvm, + APICV_INHIBIT_REASON_APIC_ID_MODIFIED); return; + } kvm_set_apicv_inhibit(apic->vcpu->kvm, APICV_INHIBIT_REASON_APIC_ID_MODIFIED); } -- 2.38.1
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