[PATCH 16/22] KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put

Marc Zyngier
2019-11-20T16:51:12Z

When the VHE code was reworked, a lot of the vgic stuff was moved around,
but the GICv4 residency code did stay untouched, meaning that we come
in and out of residency on each flush/sync, which is obviously suboptimal.

To address this, let's move things around a bit:

- Residency entry (flush) moves to vcpu_load
- Residency exit (sync) moves to vcpu_put
- On blocking (entry to WFI), we "put"
- On unblocking (exit from WFI), we "load"

Because these can nest (load/block/put/load/unblock/put, for example),
we now have per-VPE tracking of the residency state.

Additionally, vgic_v4_put gains a "need doorbell" parameter, which only
gets set to true when blocking because of a WFI. This allows a finer
control of the doorbell, which now also gets disabled as soon as
it gets signaled.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191027144234.8395-2-maz@kernel.org
---
drivers/irqchip/irq-gic-v4.c | 7 +++-
include/kvm/arm_vgic.h | 4 +--
include/linux/irqchip/arm-gic-v4.h | 2 ++
virt/kvm/arm/arm.c | 12 ++++---
virt/kvm/arm/vgic/vgic-v3.c | 4 +++
virt/kvm/arm/vgic/vgic-v4.c | 55 ++++++++++++++----------------
virt/kvm/arm/vgic/vgic.c | 4 ---
virt/kvm/arm/vgic/vgic.h | 2 --
8 files changed, 48 insertions(+), 42 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c
index 563e87ed0766..45969927cc81 100644
--- a/drivers/irqchip/irq-gic-v4.c
+++ b/drivers/irqchip/irq-gic-v4.c
@@ -141,12 +141,17 @@ static int its_send_vpe_cmd(struct its_vpe *vpe, struct its_cmd_info *info)
int its_schedule_vpe(struct its_vpe *vpe, bool on)
{
struct its_cmd_info info;
+ int ret;

WARN_ON(preemptible());

info.cmd_type = on ? SCHEDULE_VPE : DESCHEDULE_VPE;

- return its_send_vpe_cmd(vpe, &info);
+ ret = its_send_vpe_cmd(vpe, &info);
+ if (!ret)
+ vpe->resident = on;
+
+ return ret;
}

int its_invall_vpe(struct its_vpe *vpe)
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index af4f09c02bf1..4dc58d7a0010 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -396,7 +396,7 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,
int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
struct kvm_kernel_irq_routing_entry *irq_entry);

-void kvm_vgic_v4_enable_doorbell(struct kvm_vcpu *vcpu);
-void kvm_vgic_v4_disable_doorbell(struct kvm_vcpu *vcpu);
+int vgic_v4_load(struct kvm_vcpu *vcpu);
+int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db);

#endif /* __KVM_ARM_VGIC_H */
diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
index e6b155713b47..ab1396afe08a 100644
--- a/include/linux/irqchip/arm-gic-v4.h
+++ b/include/linux/irqchip/arm-gic-v4.h
@@ -35,6 +35,8 @@ struct its_vpe {
/* Doorbell interrupt */
int irq;
irq_hw_number_t vpe_db_lpi;
+ /* VPE resident */
+ bool resident;
/* VPE proxy mapping */
int vpe_proxy_event;
/*
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 86c6aa1cb58e..bd2afcf9a13f 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -322,20 +322,24 @@ void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
/*
* If we're about to block (most likely because we've just hit a
* WFI), we need to sync back the state of the GIC CPU interface
- * so that we have the lastest PMR and group enables. This ensures
+ * so that we have the latest PMR and group enables. This ensures
* that kvm_arch_vcpu_runnable has up-to-date data to decide
* whether we have pending interrupts.
+ *
+ * For the same reason, we want to tell GICv4 that we need
+ * doorbells to be signalled, should an interrupt become pending.
*/
preempt_disable();
kvm_vgic_vmcr_sync(vcpu);
+ vgic_v4_put(vcpu, true);
preempt_enable();
-
- kvm_vgic_v4_enable_doorbell(vcpu);
}

void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
{
- kvm_vgic_v4_disable_doorbell(vcpu);
+ preempt_disable();
+ vgic_v4_load(vcpu);
+ preempt_enable();
}

int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 8d69f007dd0c..48307a9eb1d8 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -664,6 +664,8 @@ void vgic_v3_load(struct kvm_vcpu *vcpu)

if (has_vhe())
__vgic_v3_activate_traps(vcpu);
+
+ WARN_ON(vgic_v4_load(vcpu));
}

void vgic_v3_vmcr_sync(struct kvm_vcpu *vcpu)
@@ -676,6 +678,8 @@ void vgic_v3_vmcr_sync(struct kvm_vcpu *vcpu)

void vgic_v3_put(struct kvm_vcpu *vcpu)
{
+ WARN_ON(vgic_v4_put(vcpu, false));
+
vgic_v3_vmcr_sync(vcpu);

kvm_call_hyp(__vgic_v3_save_aprs, vcpu);
diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index 477af6aebb97..7e1f3202968a 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -85,6 +85,10 @@ static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
{
struct kvm_vcpu *vcpu = info;

+ /* We got the message, no need to fire again */
+ if (!irqd_irq_disabled(&irq_to_desc(irq)->irq_data))
+ disable_irq_nosync(irq);
+
vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
kvm_vcpu_kick(vcpu);
@@ -192,20 +196,30 @@ void vgic_v4_teardown(struct kvm *kvm)
its_vm->vpes = NULL;
}

-int vgic_v4_sync_hwstate(struct kvm_vcpu *vcpu)
+int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db)
{
- if (!vgic_supports_direct_msis(vcpu->kvm))
+ struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
+ struct irq_desc *desc = irq_to_desc(vpe->irq);
+
+ if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
return 0;

- return its_schedule_vpe(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe, false);
+ /*
+ * If blocking, a doorbell is required. Undo the nested
+ * disable_irq() calls...
+ */
+ while (need_db && irqd_irq_disabled(&desc->irq_data))
+ enable_irq(vpe->irq);
+
+ return its_schedule_vpe(vpe, false);
}

-int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu)
+int vgic_v4_load(struct kvm_vcpu *vcpu)
{
- int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
+ struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
int err;

- if (!vgic_supports_direct_msis(vcpu->kvm))
+ if (!vgic_supports_direct_msis(vcpu->kvm) || vpe->resident)
return 0;

/*
@@ -214,11 +228,14 @@ int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu)
* doc in drivers/irqchip/irq-gic-v4.c to understand how this
* turns into a VMOVP command at the ITS level.
*/
- err = irq_set_affinity(irq, cpumask_of(smp_processor_id()));
+ err = irq_set_affinity(vpe->irq, cpumask_of(smp_processor_id()));
if (err)
return err;

- err = its_schedule_vpe(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe, true);
+ /* Disabled the doorbell, as we're about to enter the guest */
+ disable_irq_nosync(vpe->irq);
+
+ err = its_schedule_vpe(vpe, true);
if (err)
return err;

@@ -226,9 +243,7 @@ int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu)
* Now that the VPE is resident, let's get rid of a potential
* doorbell interrupt that would still be pending.
*/
- err = irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING, false);
-
- return err;
+ return irq_set_irqchip_state(vpe->irq, IRQCHIP_STATE_PENDING, false);
}

static struct vgic_its *vgic_get_its(struct kvm *kvm,
@@ -335,21 +350,3 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
mutex_unlock(&its->its_lock);
return ret;
}
-
-void kvm_vgic_v4_enable_doorbell(struct kvm_vcpu *vcpu)
-{
- if (vgic_supports_direct_msis(vcpu->kvm)) {
- int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
- if (irq)
- enable_irq(irq);
- }
-}
-
-void kvm_vgic_v4_disable_doorbell(struct kvm_vcpu *vcpu)
-{
- if (vgic_supports_direct_msis(vcpu->kvm)) {
- int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
- if (irq)
- disable_irq(irq);
- }
-}
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 45a870cb63f5..99b02ca730a8 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -857,8 +857,6 @@ void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu)
{
struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;

- WARN_ON(vgic_v4_sync_hwstate(vcpu));
-
/* An empty ap_list_head implies used_lrs == 0 */
if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head))
return;
@@ -882,8 +880,6 @@ static inline void vgic_restore_state(struct kvm_vcpu *vcpu)
/* Flush our emulation state into the GIC hardware before entering the guest. */
void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
{
- WARN_ON(vgic_v4_flush_hwstate(vcpu));
-
/*
* If there are no virtual interrupts active or pending for this
* VCPU, then there is no work to do and we can bail out without
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index 83066a81b16a..c7fefd6b1c80 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -316,7 +316,5 @@ void vgic_its_invalidate_cache(struct kvm *kvm);
bool vgic_supports_direct_msis(struct kvm *kvm);
int vgic_v4_init(struct kvm *kvm);
void vgic_v4_teardown(struct kvm *kvm);
-int vgic_v4_sync_hwstate(struct kvm_vcpu *vcpu);
-int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu);

#endif