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KVM: x86: Remove support for reporting coalesced APIC IRQs
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Since the arrival of posted interrupt support we can no longer guarantee
that coalesced IRQs are always reported to the IRQ source. Moreover,
accumulated APIC timer events could cause a busy loop when a VCPU should
rather be halted. The consensus is to remove coalesced tracking from the
LAPIC.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
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@jan-kiszka
jan-kiszka authored and Gleb Natapov committed May 14, 2013
1 parent e2858b4 commit f1ed045
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Showing 3 changed files with 32 additions and 40 deletions.
57 changes: 23 additions & 34 deletions arch/x86/kvm/lapic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -405,17 +405,17 @@ int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
return highest_irr;
}

static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
int vector, int level, int trig_mode,
unsigned long *dest_map);
static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
int vector, int level, int trig_mode,
unsigned long *dest_map);

int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
unsigned long *dest_map)
void kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
unsigned long *dest_map)
{
struct kvm_lapic *apic = vcpu->arch.apic;

return __apic_accept_irq(apic, irq->delivery_mode, irq->vector,
irq->level, irq->trig_mode, dest_map);
__apic_accept_irq(apic, irq->delivery_mode, irq->vector,
irq->level, irq->trig_mode, dest_map);
}

static int pv_eoi_put_user(struct kvm_vcpu *vcpu, u8 val)
Expand Down Expand Up @@ -608,7 +608,8 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
*r = -1;

if (irq->shorthand == APIC_DEST_SELF) {
*r = kvm_apic_set_irq(src->vcpu, irq, dest_map);
kvm_apic_set_irq(src->vcpu, irq, dest_map);
*r = 1;
return true;
}

Expand Down Expand Up @@ -653,7 +654,8 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
continue;
if (*r < 0)
*r = 0;
*r += kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
*r += 1;
}

ret = true;
Expand All @@ -662,15 +664,11 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
return ret;
}

/*
* Add a pending IRQ into lapic.
* Return 1 if successfully added and 0 if discarded.
*/
static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
int vector, int level, int trig_mode,
unsigned long *dest_map)
/* Set an IRQ pending in the lapic. */
static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
int vector, int level, int trig_mode,
unsigned long *dest_map)
{
int result = 0;
struct kvm_vcpu *vcpu = apic->vcpu;

switch (delivery_mode) {
Expand All @@ -684,13 +682,10 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
if (dest_map)
__set_bit(vcpu->vcpu_id, dest_map);

if (kvm_x86_ops->deliver_posted_interrupt) {
result = 1;
if (kvm_x86_ops->deliver_posted_interrupt)
kvm_x86_ops->deliver_posted_interrupt(vcpu, vector);
} else {
result = !apic_test_and_set_irr(vector, apic);

if (!result) {
else {
if (apic_test_and_set_irr(vector, apic)) {
if (trig_mode)
apic_debug("level trig mode repeatedly "
"for vector %d", vector);
Expand All @@ -702,7 +697,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
}
out:
trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode,
trig_mode, vector, !result);
trig_mode, vector, false);
break;

case APIC_DM_REMRD:
Expand All @@ -714,14 +709,12 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
break;

case APIC_DM_NMI:
result = 1;
kvm_inject_nmi(vcpu);
kvm_vcpu_kick(vcpu);
break;

case APIC_DM_INIT:
if (!trig_mode || level) {
result = 1;
/* assumes that there are only KVM_APIC_INIT/SIPI */
apic->pending_events = (1UL << KVM_APIC_INIT);
/* make sure pending_events is visible before sending
Expand All @@ -738,7 +731,6 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
case APIC_DM_STARTUP:
apic_debug("SIPI to vcpu %d vector 0x%02x\n",
vcpu->vcpu_id, vector);
result = 1;
apic->sipi_vector = vector;
/* make sure sipi_vector is visible for the receiver */
smp_wmb();
Expand All @@ -760,7 +752,6 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
delivery_mode);
break;
}
return result;
}

int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
Expand Down Expand Up @@ -1470,7 +1461,7 @@ int apic_has_pending_timer(struct kvm_vcpu *vcpu)
return 0;
}

int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
void kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
{
u32 reg = kvm_apic_get_reg(apic, lvt_type);
int vector, mode, trig_mode;
Expand All @@ -1479,10 +1470,8 @@ int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
vector = reg & APIC_VECTOR_MASK;
mode = reg & APIC_MODE_MASK;
trig_mode = reg & APIC_LVT_LEVEL_TRIGGER;
return __apic_accept_irq(apic, mode, vector, 1, trig_mode,
NULL);
__apic_accept_irq(apic, mode, vector, 1, trig_mode, NULL);
}
return 0;
}

void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu)
Expand Down Expand Up @@ -1608,8 +1597,8 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
return;

if (atomic_read(&apic->lapic_timer.pending) > 0) {
if (kvm_apic_local_deliver(apic, APIC_LVTT))
atomic_dec(&apic->lapic_timer.pending);
kvm_apic_local_deliver(apic, APIC_LVTT);
atomic_set(&apic->lapic_timer.pending, 0);
}
}

Expand Down
6 changes: 3 additions & 3 deletions arch/x86/kvm/lapic.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -57,9 +57,9 @@ void kvm_apic_update_tmr(struct kvm_vcpu *vcpu, u32 *tmr);
void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
int kvm_apic_match_physical_addr(struct kvm_lapic *apic, u16 dest);
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,
unsigned long *dest_map);
int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
void kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
unsigned long *dest_map);
void 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, unsigned long *dest_map);
Expand Down
9 changes: 6 additions & 3 deletions virt/kvm/irq_comm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
if (!kvm_is_dm_lowest_prio(irq)) {
if (r < 0)
r = 0;
r += kvm_apic_set_irq(vcpu, irq, dest_map);
kvm_apic_set_irq(vcpu, irq, dest_map);
r++;
} else if (kvm_lapic_enabled(vcpu)) {
if (!lowest)
lowest = vcpu;
Expand All @@ -100,8 +101,10 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
}
}

if (lowest)
r = kvm_apic_set_irq(lowest, irq, dest_map);
if (lowest) {
kvm_apic_set_irq(lowest, irq, dest_map);
r = 1;
}

return r;
}
Expand Down

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