Hi Sean
On 9/2/2022 7:22 PM, 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>
Reviewed-by: Maxim Levitsky <mlevitsk@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 6b2f538b8fd0..75748c380ceb 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]) {
Should this be checking if the cluster[ldr] is pointing to the same
struct apic instead? For example:
if (!is_power_of_2(mask) || cluster[ldr] != apic)
From my observation, the kvm_recalculate_apic_map() can be called many
times, and the cluster[ldr] could have already been assigned from the
previous invocation. So, as long as it is the same, it should be okay.
Best Regards,
Suravee
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,
