From 2970052481b9f93e1849f5d4a1065e9fafc8d662 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 6 Jan 2023 01:12:54 +0000 Subject: [PATCH] KVM: x86: Disable APIC logical map if vCPUs are aliased in logical mode Disable the optimized APIC logical map if multiple vCPUs are aliased to the same logical ID. Architecturally, all CPUs whose logical ID matches the MDA are supposed to receive the interrupt; overwriting existing map entries can result in missed IPIs. Fixes: 1e08ec4a130e ("KVM: optimize apic interrupt delivery") Signed-off-by: Sean Christopherson Reviewed-by: Maxim Levitsky Message-Id: <20230106011306.85230-22-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index dca87bb6dd1a..9c0554bae3b1 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -346,11 +346,12 @@ void kvm_recalculate_apic_map(struct kvm *kvm) if (!mask) continue; - if (!is_power_of_2(mask)) { + ldr = ffs(mask) - 1; + if (!is_power_of_2(mask) || cluster[ldr]) { new->logical_mode = KVM_APIC_MODE_MAP_DISABLED; continue; } - cluster[ffs(mask) - 1] = apic; + cluster[ldr] = apic; } out: old = rcu_dereference_protected(kvm->arch.apic_map,