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KVM: x86: dynamic kvm_apic_map

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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>
This commit is contained in:
Radim Krčmář 2016-07-12 22:09:20 +02:00 committed by Paolo Bonzini
parent e45115b62f
commit 0ca52e7b81
3 changed files with 16 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/include/asm/kvm_host.h
View File

@ -682,11 +682,12 @@ struct kvm_arch_memory_slot {
struct kvm_apic_map { struct kvm_apic_map {
struct rcu_head rcu; struct rcu_head rcu;
u8 mode; u8 mode;
struct kvm_lapic *phys_map[256]; u32 max_apic_id;
union { union {
struct kvm_lapic *xapic_flat_map[8]; struct kvm_lapic *xapic_flat_map[8];
struct kvm_lapic *xapic_cluster_map[16][4]; struct kvm_lapic *xapic_cluster_map[16][4];
}; };
struct kvm_lapic *phys_map[];
}; };
/* Hyper-V emulation context */ /* Hyper-V emulation context */

18
arch/x86/kvm/lapic.c
View File

@ -120,7 +120,7 @@ static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
switch (map->mode) { switch (map->mode) {
case KVM_APIC_MODE_X2APIC: { case KVM_APIC_MODE_X2APIC: {
u32 offset = (dest_id >> 16) * 16; 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) { if (offset <= max_apic_id) {
u8 cluster_size = min(max_apic_id - offset + 1, 16U); u8 cluster_size = min(max_apic_id - offset + 1, 16U);
@ -152,14 +152,22 @@ static void recalculate_apic_map(struct kvm *kvm)
struct kvm_apic_map *new, *old = NULL; struct kvm_apic_map *new, *old = NULL;
struct kvm_vcpu *vcpu; struct kvm_vcpu *vcpu;
int i; int i;
u32 max_id = 255;
new = kzalloc(sizeof(struct kvm_apic_map), GFP_KERNEL);
mutex_lock(&kvm->arch.apic_map_lock); 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) if (!new)
goto out; goto out;
new->max_apic_id = max_id;
kvm_for_each_vcpu(i, vcpu, kvm) { kvm_for_each_vcpu(i, vcpu, kvm) {
struct kvm_lapic *apic = vcpu->arch.apic; struct kvm_lapic *apic = vcpu->arch.apic;
struct kvm_lapic **cluster; struct kvm_lapic **cluster;
@ -172,7 +180,7 @@ static void recalculate_apic_map(struct kvm *kvm)
aid = kvm_apic_id(apic); aid = kvm_apic_id(apic);
ldr = kvm_lapic_get_reg(apic, APIC_LDR); 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; new->phys_map[aid] = apic;
if (apic_x2apic_mode(apic)) { if (apic_x2apic_mode(apic)) {
@ -710,7 +718,7 @@ static inline bool kvm_apic_map_get_dest_lapic(struct kvm *kvm,
return false; return false;
if (irq->dest_mode == APIC_DEST_PHYSICAL) { 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; *bitmap = 0;
} else { } else {
*dst = &map->phys_map[irq->dest_id]; *dst = &map->phys_map[irq->dest_id];

2
arch/x86/kvm/lapic.h
View File

@ -200,7 +200,7 @@ static inline int kvm_lapic_latched_init(struct kvm_vcpu *vcpu)
return lapic_in_kernel(vcpu) && test_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events); return lapic_in_kernel(vcpu) && test_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
} }
static inline int kvm_apic_id(struct kvm_lapic *apic) static inline u32 kvm_apic_id(struct kvm_lapic *apic)
{ {
return (kvm_lapic_get_reg(apic, APIC_ID) >> 24) & 0xff; return (kvm_lapic_get_reg(apic, APIC_ID) >> 24) & 0xff;
} }