KVM: use smp_send_reschedule in kvm_vcpu_kick
KVM uses a function call IPI to cause the exit of a guest running on a
physical cpu. For virtual interrupt notification there is no need to
wait on IPI receival, or to execute any function.
This is exactly what the reschedule IPI does, without the overhead
of function IPI. So use it instead of smp_call_function_single in
kvm_vcpu_kick.
Also change the "guest_mode" variable to a bit in vcpu->requests, and
use that to collapse multiple IPI's that would be issued between the
first one and zeroing of guest mode.
This allows kvm_vcpu_kick to called with interrupts disabled.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/ia64/kernel/irq_ia64.c b/arch/ia64/kernel/irq_ia64.c
index acc4d19..b448197 100644
--- a/arch/ia64/kernel/irq_ia64.c
+++ b/arch/ia64/kernel/irq_ia64.c
@@ -610,6 +610,9 @@
.name = "IPI"
};
+/*
+ * KVM uses this interrupt to force a cpu out of guest mode
+ */
static struct irqaction resched_irqaction = {
.handler = dummy_handler,
.flags = IRQF_DISABLED,
diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index be4413e..80c57b0 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -668,7 +668,7 @@
host_ctx = kvm_get_host_context(vcpu);
guest_ctx = kvm_get_guest_context(vcpu);
- vcpu->guest_mode = 1;
+ clear_bit(KVM_REQ_KICK, &vcpu->requests);
r = kvm_vcpu_pre_transition(vcpu);
if (r < 0)
@@ -685,7 +685,7 @@
kvm_vcpu_post_transition(vcpu);
vcpu->arch.launched = 1;
- vcpu->guest_mode = 0;
+ set_bit(KVM_REQ_KICK, &vcpu->requests);
local_irq_enable();
/*
@@ -1879,24 +1879,18 @@
{
}
-static void vcpu_kick_intr(void *info)
-{
-#ifdef DEBUG
- struct kvm_vcpu *vcpu = (struct kvm_vcpu *)info;
- printk(KERN_DEBUG"vcpu_kick_intr %p \n", vcpu);
-#endif
-}
-
void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
- int ipi_pcpu = vcpu->cpu;
- int cpu = get_cpu();
+ int me;
+ int cpu = vcpu->cpu;
if (waitqueue_active(&vcpu->wq))
wake_up_interruptible(&vcpu->wq);
- if (vcpu->guest_mode && cpu != ipi_pcpu)
- smp_call_function_single(ipi_pcpu, vcpu_kick_intr, vcpu, 0);
+ me = get_cpu();
+ if (cpu != me && (unsigned) cpu < nr_cpu_ids && cpu_online(cpu))
+ if (!test_and_set_bit(KVM_REQ_KICK, &vcpu->requests))
+ smp_send_reschedule(cpu);
put_cpu();
}
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 13f33ea..3b2e55e 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -172,6 +172,9 @@
{
ack_APIC_irq();
inc_irq_stat(irq_resched_count);
+ /*
+ * KVM uses this interrupt to force a cpu out of guest mode
+ */
}
void smp_call_function_interrupt(struct pt_regs *regs)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7592770..3c4c327 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3230,6 +3230,9 @@
local_irq_disable();
+ clear_bit(KVM_REQ_KICK, &vcpu->requests);
+ smp_mb__after_clear_bit();
+
if (vcpu->requests || need_resched() || signal_pending(current)) {
local_irq_enable();
preempt_enable();
@@ -3237,13 +3240,6 @@
goto out;
}
- vcpu->guest_mode = 1;
- /*
- * Make sure that guest_mode assignment won't happen after
- * testing the pending IRQ vector bitmap.
- */
- smp_wmb();
-
if (vcpu->arch.exception.pending)
__queue_exception(vcpu);
else
@@ -3288,7 +3284,7 @@
set_debugreg(vcpu->arch.host_dr6, 6);
set_debugreg(vcpu->arch.host_dr7, 7);
- vcpu->guest_mode = 0;
+ set_bit(KVM_REQ_KICK, &vcpu->requests);
local_irq_enable();
++vcpu->stat.exits;
@@ -4571,30 +4567,20 @@
|| vcpu->arch.nmi_pending;
}
-static void vcpu_kick_intr(void *info)
-{
-#ifdef DEBUG
- struct kvm_vcpu *vcpu = (struct kvm_vcpu *)info;
- printk(KERN_DEBUG "vcpu_kick_intr %p \n", vcpu);
-#endif
-}
-
void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
- int ipi_pcpu = vcpu->cpu;
- int cpu;
+ int me;
+ int cpu = vcpu->cpu;
if (waitqueue_active(&vcpu->wq)) {
wake_up_interruptible(&vcpu->wq);
++vcpu->stat.halt_wakeup;
}
- /*
- * We may be called synchronously with irqs disabled in guest mode,
- * So need not to call smp_call_function_single() in that case.
- */
- cpu = get_cpu();
- if (vcpu->guest_mode && vcpu->cpu != cpu)
- smp_call_function_single(ipi_pcpu, vcpu_kick_intr, vcpu, 0);
+
+ me = get_cpu();
+ if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
+ if (!test_and_set_bit(KVM_REQ_KICK, &vcpu->requests))
+ smp_send_reschedule(cpu);
put_cpu();
}