[PATCH v2 15/23] KVM: x86: Explicitly skip adding vCPU to optimized logical map if LDR==0

Sean Christopherson
2022-09-03T00:24:21Z

Explicitly skip adding a vCPU to the optimized map of logical IDs if the
the vCPU's LDR is '0', i.e. if the vCPU will never response to logical
mode interrupts. KVM already skips the vCPU in this case, but relies on
kvm_apic_map_get_logical_dest() to generate mask==0. KVM still needs the
mask=0 check as a non-zero LDR can yield mask==0 depending on the mode,
but explicitly handling the LDR will make it simpler to clean up the
logical mode tracking in the future.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/lapic.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 4c5f49c4d4f1..80528d86f010 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -318,10 +318,12 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
continue;

ldr = kvm_lapic_get_reg(apic, APIC_LDR);
+ if (!ldr)
+ continue;

if (apic_x2apic_mode(apic)) {
new->mode |= KVM_APIC_MODE_X2APIC;
- } else if (ldr) {
+ } else {
ldr = GET_APIC_LOGICAL_ID(ldr);
if (kvm_lapic_get_reg(apic, APIC_DFR) == APIC_DFR_FLAT)
new->mode |= KVM_APIC_MODE_XAPIC_FLAT;
--
2.37.2.789.g6183377224-goog