On Wed, 2022-08-31 at 00:35 +0000, Sean Christopherson wrote:
> 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 <seanjc@xxxxxxxxxx>
> ---
> 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 82278acae95b..d537b51295d6 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -303,12 +303,13 @@ 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->mode = KVM_APIC_MODE_XAPIC_FLAT |
> KVM_APIC_MODE_XAPIC_CLUSTER;
> continue;
> }
> - cluster[ffs(mask) - 1] = apic;
> + cluster[ldr] = apic;
> }
> out:
> old = rcu_dereference_protected(kvm->arch.apic_map,
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
