Skip to content

Commit

Permalink
KVM: optimize apic interrupt delivery
Browse files Browse the repository at this point in the history 
Most interrupt are delivered to only one vcpu. Use pre-build tables to
find interrupt destination instead of looping through all vcpus. In case
of logical mode loop only through vcpus in a logical cluster irq is sent
to.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
  • Loading branch information
Gleb Natapov authored and Avi Kivity committed Sep 20, 2012
1 parent 1d86b5c commit 1e08ec4
Show file tree
Hide file tree
Showing 5 changed files with 199 additions and 13 deletions.
12 changes: 12 additions & 0 deletions arch/x86/include/asm/kvm_host.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -525,6 +525,16 @@ struct kvm_arch_memory_slot {
struct kvm_lpage_info *lpage_info[KVM_NR_PAGE_SIZES - 1];
};

struct kvm_apic_map {
struct rcu_head rcu;
u8 ldr_bits;
/* fields bellow are used to decode ldr values in different modes */
u32 cid_shift, cid_mask, lid_mask;
struct kvm_lapic *phys_map[256];
/* first index is cluster id second is cpu id in a cluster */
struct kvm_lapic *logical_map[16][16];
};

struct kvm_arch {
unsigned int n_used_mmu_pages;
unsigned int n_requested_mmu_pages;
Expand All @@ -542,6 +552,8 @@ struct kvm_arch {
struct kvm_ioapic *vioapic;
struct kvm_pit *vpit;
int vapics_in_nmi_mode;
struct mutex apic_map_lock;
struct kvm_apic_map *apic_map;

unsigned int tss_addr;
struct page *apic_access_page;
Expand Down
188 changes: 176 additions & 12 deletions arch/x86/kvm/lapic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -140,11 +140,110 @@ static inline int apic_enabled(struct kvm_lapic *apic)
(LVT_MASK | APIC_MODE_MASK | APIC_INPUT_POLARITY | \
APIC_LVT_REMOTE_IRR | APIC_LVT_LEVEL_TRIGGER)

static inline int apic_x2apic_mode(struct kvm_lapic *apic)
{
return apic->vcpu->arch.apic_base & X2APIC_ENABLE;
}

static inline int kvm_apic_id(struct kvm_lapic *apic)
{
return (kvm_apic_get_reg(apic, APIC_ID) >> 24) & 0xff;
}

static inline u16 apic_cluster_id(struct kvm_apic_map *map, u32 ldr)
{
u16 cid;
ldr >>= 32 - map->ldr_bits;
cid = (ldr >> map->cid_shift) & map->cid_mask;

BUG_ON(cid >= ARRAY_SIZE(map->logical_map));

return cid;
}

static inline u16 apic_logical_id(struct kvm_apic_map *map, u32 ldr)
{
ldr >>= (32 - map->ldr_bits);
return ldr & map->lid_mask;
}

static void recalculate_apic_map(struct kvm *kvm)
{
struct kvm_apic_map *new, *old = NULL;
struct kvm_vcpu *vcpu;
int i;

new = kzalloc(sizeof(struct kvm_apic_map), GFP_KERNEL);

mutex_lock(&kvm->arch.apic_map_lock);

if (!new)
goto out;

new->ldr_bits = 8;
/* flat mode is default */
new->cid_shift = 8;
new->cid_mask = 0;
new->lid_mask = 0xff;

kvm_for_each_vcpu(i, vcpu, kvm) {
struct kvm_lapic *apic = vcpu->arch.apic;
u16 cid, lid;
u32 ldr;

if (!kvm_apic_present(vcpu))
continue;

/*
* All APICs have to be configured in the same mode by an OS.
* We take advatage of this while building logical id loockup
* table. After reset APICs are in xapic/flat mode, so if we
* find apic with different setting we assume this is the mode
* OS wants all apics to be in; build lookup table accordingly.
*/
if (apic_x2apic_mode(apic)) {
new->ldr_bits = 32;
new->cid_shift = 16;
new->cid_mask = new->lid_mask = 0xffff;
} else if (kvm_apic_sw_enabled(apic) &&
!new->cid_mask /* flat mode */ &&
kvm_apic_get_reg(apic, APIC_DFR) == APIC_DFR_CLUSTER) {
new->cid_shift = 4;
new->cid_mask = 0xf;
new->lid_mask = 0xf;
}

new->phys_map[kvm_apic_id(apic)] = apic;

ldr = kvm_apic_get_reg(apic, APIC_LDR);
cid = apic_cluster_id(new, ldr);
lid = apic_logical_id(new, ldr);

if (lid)
new->logical_map[cid][ffs(lid) - 1] = apic;
}
out:
old = rcu_dereference_protected(kvm->arch.apic_map,
lockdep_is_held(&kvm->arch.apic_map_lock));
rcu_assign_pointer(kvm->arch.apic_map, new);
mutex_unlock(&kvm->arch.apic_map_lock);

if (old)
kfree_rcu(old, rcu);
}

static inline void kvm_apic_set_id(struct kvm_lapic *apic, u8 id)
{
apic_set_reg(apic, APIC_ID, id << 24);
recalculate_apic_map(apic->vcpu->kvm);
}

static inline void kvm_apic_set_ldr(struct kvm_lapic *apic, u32 id)
{
apic_set_reg(apic, APIC_LDR, id);
recalculate_apic_map(apic->vcpu->kvm);
}

static inline int apic_lvt_enabled(struct kvm_lapic *apic, int lvt_type)
{
return !(kvm_apic_get_reg(apic, lvt_type) & APIC_LVT_MASKED);
Expand Down Expand Up @@ -194,11 +293,6 @@ void kvm_apic_set_version(struct kvm_vcpu *vcpu)
apic_set_reg(apic, APIC_LVR, v);
}

static inline int apic_x2apic_mode(struct kvm_lapic *apic)
{
return apic->vcpu->arch.apic_base & X2APIC_ENABLE;
}

static const unsigned int apic_lvt_mask[APIC_LVT_NUM] = {
LVT_MASK , /* part LVTT mask, timer mode mask added at runtime */
LVT_MASK | APIC_MODE_MASK, /* LVTTHMR */
Expand Down Expand Up @@ -483,6 +577,72 @@ int kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
return result;
}

bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq, int *r)
{
struct kvm_apic_map *map;
unsigned long bitmap = 1;
struct kvm_lapic **dst;
int i;
bool ret = false;

*r = -1;

if (irq->shorthand == APIC_DEST_SELF) {
*r = kvm_apic_set_irq(src->vcpu, irq);
return true;
}

if (irq->shorthand)
return false;

rcu_read_lock();
map = rcu_dereference(kvm->arch.apic_map);

if (!map)
goto out;

if (irq->dest_mode == 0) { /* physical mode */
if (irq->delivery_mode == APIC_DM_LOWEST ||
irq->dest_id == 0xff)
goto out;
dst = &map->phys_map[irq->dest_id & 0xff];
} else {
u32 mda = irq->dest_id << (32 - map->ldr_bits);

dst = map->logical_map[apic_cluster_id(map, mda)];

bitmap = apic_logical_id(map, mda);

if (irq->delivery_mode == APIC_DM_LOWEST) {
int l = -1;
for_each_set_bit(i, &bitmap, 16) {
if (!dst[i])
continue;
if (l < 0)
l = i;
else if (kvm_apic_compare_prio(dst[i]->vcpu, dst[l]->vcpu) < 0)
l = i;
}

bitmap = (l >= 0) ? 1 << l : 0;
}
}

for_each_set_bit(i, &bitmap, 16) {
if (!dst[i])
continue;
if (*r < 0)
*r = 0;
*r += kvm_apic_set_irq(dst[i]->vcpu, irq);
}

ret = true;
out:
rcu_read_unlock();
return ret;
}

/*
* Add a pending IRQ into lapic.
* Return 1 if successfully added and 0 if discarded.
Expand Down Expand Up @@ -886,7 +1046,7 @@ static int apic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
switch (reg) {
case APIC_ID: /* Local APIC ID */
if (!apic_x2apic_mode(apic))
apic_set_reg(apic, APIC_ID, val);
kvm_apic_set_id(apic, val >> 24);
else
ret = 1;
break;
Expand All @@ -902,15 +1062,16 @@ static int apic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)

case APIC_LDR:
if (!apic_x2apic_mode(apic))
apic_set_reg(apic, APIC_LDR, val & APIC_LDR_MASK);
kvm_apic_set_ldr(apic, val & APIC_LDR_MASK);
else
ret = 1;
break;

case APIC_DFR:
if (!apic_x2apic_mode(apic))
if (!apic_x2apic_mode(apic)) {
apic_set_reg(apic, APIC_DFR, val | 0x0FFFFFFF);
else
recalculate_apic_map(apic->vcpu->kvm);
} else
ret = 1;
break;

Expand Down Expand Up @@ -1141,6 +1302,7 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
static_key_slow_dec_deferred(&apic_hw_disabled);
else
static_key_slow_inc(&apic_hw_disabled.key);
recalculate_apic_map(vcpu->kvm);
}

if (!kvm_vcpu_is_bsp(apic->vcpu))
Expand All @@ -1150,7 +1312,7 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
if (apic_x2apic_mode(apic)) {
u32 id = kvm_apic_id(apic);
u32 ldr = ((id & ~0xf) << 16) | (1 << (id & 0xf));
apic_set_reg(apic, APIC_LDR, ldr);
kvm_apic_set_ldr(apic, ldr);
}
apic->base_address = apic->vcpu->arch.apic_base &
MSR_IA32_APICBASE_BASE;
Expand All @@ -1175,7 +1337,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
/* Stop the timer in case it's a reset to an active apic */
hrtimer_cancel(&apic->lapic_timer.timer);

apic_set_reg(apic, APIC_ID, vcpu->vcpu_id << 24);
kvm_apic_set_id(apic, vcpu->vcpu_id);
kvm_apic_set_version(apic->vcpu);

for (i = 0; i < APIC_LVT_NUM; i++)
Expand All @@ -1186,7 +1348,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
apic_set_reg(apic, APIC_DFR, 0xffffffffU);
apic_set_spiv(apic, 0xff);
apic_set_reg(apic, APIC_TASKPRI, 0);
apic_set_reg(apic, APIC_LDR, 0);
kvm_apic_set_ldr(apic, 0);
apic_set_reg(apic, APIC_ESR, 0);
apic_set_reg(apic, APIC_ICR, 0);
apic_set_reg(apic, APIC_ICR2, 0);
Expand Down Expand Up @@ -1404,6 +1566,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
/* set SPIV separately to get count of SW disabled APICs right */
apic_set_spiv(apic, *((u32 *)(s->regs + APIC_SPIV)));
memcpy(vcpu->arch.apic->regs, s->regs, sizeof *s);
/* call kvm_apic_set_id() to put apic into apic_map */
kvm_apic_set_id(apic, kvm_apic_id(apic));
kvm_apic_set_version(vcpu);

apic_update_ppr(apic);
Expand Down
3 changes: 3 additions & 0 deletions arch/x86/kvm/lapic.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,9 @@ int kvm_apic_match_logical_addr(struct kvm_lapic *apic, u8 mda);
int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq);
int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);

bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq, int *r);

u64 kvm_get_apic_base(struct kvm_vcpu *vcpu);
void kvm_set_apic_base(struct kvm_vcpu *vcpu, u64 data);
void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
Expand Down
2 changes: 2 additions & 0 deletions arch/x86/kvm/x86.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6270,6 +6270,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);

raw_spin_lock_init(&kvm->arch.tsc_write_lock);
mutex_init(&kvm->arch.apic_map_lock);

return 0;
}
Expand Down Expand Up @@ -6322,6 +6323,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
put_page(kvm->arch.apic_access_page);
if (kvm->arch.ept_identity_pagetable)
put_page(kvm->arch.ept_identity_pagetable);
kfree(rcu_dereference_check(kvm->arch.apic_map, 1));
}

void kvm_arch_free_memslot(struct kvm_memory_slot *free,
Expand Down
7 changes: 6 additions & 1 deletion virt/kvm/irq_comm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,8 +68,13 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_vcpu *vcpu, *lowest = NULL;

if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
kvm_is_dm_lowest_prio(irq))
kvm_is_dm_lowest_prio(irq)) {
printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
irq->delivery_mode = APIC_DM_FIXED;
}

if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r))
return r;

kvm_for_each_vcpu(i, vcpu, kvm) {
if (!kvm_apic_present(vcpu))
Expand Down

0 comments on commit 1e08ec4

Please sign in to comment.