KVM: x86: dynamic kvm_apic_map
x2APIC supports up to 2^32-1 LAPICs, but most guest in coming years will
probably has fewer VCPUs. Dynamic size saves memory at the cost of
turning one constant into a variable.
apic_map mutex had to be moved before allocation to avoid races with cpu
hotplug.
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 9880d03..224fc1c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -120,7 +120,7 @@
switch (map->mode) {
case KVM_APIC_MODE_X2APIC: {
u32 offset = (dest_id >> 16) * 16;
- u32 max_apic_id = ARRAY_SIZE(map->phys_map) - 1;
+ u32 max_apic_id = map->max_apic_id;
if (offset <= max_apic_id) {
u8 cluster_size = min(max_apic_id - offset + 1, 16U);
@@ -152,14 +152,22 @@
struct kvm_apic_map *new, *old = NULL;
struct kvm_vcpu *vcpu;
int i;
-
- new = kzalloc(sizeof(struct kvm_apic_map), GFP_KERNEL);
+ u32 max_id = 255;
mutex_lock(&kvm->arch.apic_map_lock);
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ if (kvm_apic_present(vcpu))
+ max_id = max(max_id, kvm_apic_id(vcpu->arch.apic));
+
+ new = kzalloc(sizeof(struct kvm_apic_map) +
+ sizeof(struct kvm_lapic *) * (max_id + 1), GFP_KERNEL);
+
if (!new)
goto out;
+ new->max_apic_id = max_id;
+
kvm_for_each_vcpu(i, vcpu, kvm) {
struct kvm_lapic *apic = vcpu->arch.apic;
struct kvm_lapic **cluster;
@@ -172,7 +180,7 @@
aid = kvm_apic_id(apic);
ldr = kvm_lapic_get_reg(apic, APIC_LDR);
- if (aid < ARRAY_SIZE(new->phys_map))
+ if (aid <= new->max_apic_id)
new->phys_map[aid] = apic;
if (apic_x2apic_mode(apic)) {
@@ -710,7 +718,7 @@
return false;
if (irq->dest_mode == APIC_DEST_PHYSICAL) {
- if (irq->dest_id >= ARRAY_SIZE(map->phys_map)) {
+ if (irq->dest_id > map->max_apic_id) {
*bitmap = 0;
} else {
*dst = &map->phys_map[irq->dest_id];