diff mbox series

[v5,21/33] KVM: x86: Disable APIC logical map if vCPUs are aliased in logical mode

Message ID 20230106011306.85230-22-seanjc@google.com
State New
Headers
Series KVM: x86: AVIC and local APIC fixes+cleanups |

Commit Message

Sean Christopherson Jan. 6, 2023, 1:12 a.m. UTC 
  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@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/lapic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff mbox series

Patch

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,