[PATCH 09/10] ARM: KVM: vgic: reduce the number of vcpu kick

Christoffer Dall
2012-09-15T15:38:30Z

If we have level interrupts already programmed to fire on a vcpu,
there is no reason to kick it after injecting a new interrupt,
as we're guaranteed that we'll exit when the level interrupt will
be EOId (VGIC_LR_EOI is set).

The exit will force a reload of the VGIC, injecting the new interrupts.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
---
arch/arm/include/asm/kvm_vgic.h | 10 ++++++++++
arch/arm/kvm/arm.c | 10 +++++++++-
arch/arm/kvm/vgic.c | 10 ++++++++--
3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/kvm_vgic.h b/arch/arm/include/asm/kvm_vgic.h
index c5601f2..d722541 100644
--- a/arch/arm/include/asm/kvm_vgic.h
+++ b/arch/arm/include/asm/kvm_vgic.h
@@ -213,6 +213,9 @@ struct vgic_cpu {
u32 vgic_elrsr[2]; /* Saved only */
u32 vgic_apr;
u32 vgic_lr[64]; /* A15 has only 4... */
+
+ /* Number of level-triggered interrupt in progress */
+ atomic_t irq_active_count;
#endif
};

@@ -249,6 +252,8 @@ bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
struct kvm_exit_mmio *mmio);

#define irqchip_in_kernel(k) (!!((k)->arch.vgic.vctrl_base))
+#define vgic_active_irq(v) (atomic_read(&(v)->arch.vgic_cpu.irq_active_count) == 0)
+
#else
static inline int kvm_vgic_hyp_init(void)
{
@@ -285,6 +290,11 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
{
return 0;
}
+
+static inline int vgic_active_irq(struct kvm_vcpu *vcpu)
+{
+ return 0;
+}
#endif

#endif
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index fdd69ef..b959863 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -95,7 +95,15 @@ int kvm_arch_hardware_enable(void *garbage)

int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
- return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
+ if (kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE) {
+ if (vgic_active_irq(vcpu) &&
+ cmpxchg(&vcpu->mode, EXITING_GUEST_MODE, IN_GUEST_MODE) == EXITING_GUEST_MODE)
+ return 0;
+
+ return 1;
+ }
+
+ return 0;
}

void kvm_arch_hardware_disable(void *garbage)
diff --git a/arch/arm/kvm/vgic.c b/arch/arm/kvm/vgic.c
index fc2a138..63fe0dd 100644
--- a/arch/arm/kvm/vgic.c
+++ b/arch/arm/kvm/vgic.c
@@ -674,8 +674,10 @@ static bool vgic_queue_irq(struct kvm_vcpu *vcpu, u8 sgi_source_id, int irq)
kvm_debug("LR%d piggyback for IRQ%d %x\n", lr, irq, vgic_cpu->vgic_lr[lr]);
BUG_ON(!test_bit(lr, vgic_cpu->lr_used));
vgic_cpu->vgic_lr[lr] |= VGIC_LR_PENDING_BIT;
- if (is_level)
+ if (is_level) {
vgic_cpu->vgic_lr[lr] |= VGIC_LR_EOI;
+ atomic_inc(&vgic_cpu->irq_active_count);
+ }
return true;
}

@@ -687,8 +689,10 @@ static bool vgic_queue_irq(struct kvm_vcpu *vcpu, u8 sgi_source_id, int irq)

kvm_debug("LR%d allocated for IRQ%d %x\n", lr, irq, sgi_source_id);
vgic_cpu->vgic_lr[lr] = MK_LR_PEND(sgi_source_id, irq);
- if (is_level)
+ if (is_level) {
vgic_cpu->vgic_lr[lr] |= VGIC_LR_EOI;
+ atomic_inc(&vgic_cpu->irq_active_count);
+ }

vgic_cpu->vgic_irq_lr_map[irq] = lr;
clear_bit(lr, (unsigned long *)vgic_cpu->vgic_elrsr);
@@ -963,6 +967,8 @@ static irqreturn_t vgic_maintenance_handler(int irq, void *data)

vgic_bitmap_set_irq_val(&dist->irq_active,
vcpu->vcpu_id, irq, 0);
+ atomic_dec(&vgic_cpu->irq_active_count);
+ smp_mb();
vgic_cpu->vgic_lr[lr] &= ~VGIC_LR_EOI;
writel_relaxed(vgic_cpu->vgic_lr[lr],
dist->vctrl_base + GICH_LR0 + (lr << 2));