Drop the duplicate calculation of the logical "index", which ends up
being the same for x2APIC vs. xAPIC: cluster + bit number.
Note, the existing code is a mess and uses ffs(), which is 1-based, and
__ffs(), which is 0-based, for the exact same calculation, i.e. replacing
"ffs(bitmap) - 1" with "__ffs(bitmap)" is intentional.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/svm/avic.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 8c9cad96008e..05a1cde8175c 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -407,12 +407,14 @@ static int avic_kick_target_vcpus_fast(struct kvm *kvm, struct kvm_lapic *source
AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK;
} else {
/*
- * For x2APIC logical mode, cannot leverage the index.
- * Instead, calculate physical ID from logical ID in ICRH.
+ * For x2APIC, the logical APIC ID is a read-only value
+ * that is derived from the x2APIC ID, thus the x2APIC
+ * ID can be found by reversing the calculation (done
+ * above). Note, bits 31:20 of the x2APIC ID are not
+ * propagated to the logical ID, but KVM limits the
+ * x2APIC ID limited to KVM_MAX_VCPU_IDS.
*/
- int apic = ffs(bitmap) - 1;
-
- l1_physical_id = cluster + apic;
+ l1_physical_id = logid_index;
}
}
--
2.37.2.672.g94769d06f0-goog
