[PATCH v4 6/9] KVM: arm64: vgic: Implement SW-driven deactivation

Marc Zyngier
2021-06-01T10:40:26Z

In order to deal with these systems that do not offer HW-based
deactivation of interrupts, let implement a SW-based approach:

- When the irq is queued into a LR, treat it as a pure virtual
interrupt and set the EOI flag in the LR.

- When the interrupt state is read back from the LR, force a
deactivation when the state is invalid (neither active nor
pending)

Interrupts requiring such treatment get the VGIC_SW_RESAMPLE flag.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/vgic/vgic-v2.c | 19 +++++++++++++++----
arch/arm64/kvm/vgic/vgic-v3.c | 19 +++++++++++++++----
include/kvm/arm_vgic.h | 10 ++++++++++
3 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
index 11934c2af2f4..2c580204f1dc 100644
--- a/arch/arm64/kvm/vgic/vgic-v2.c
+++ b/arch/arm64/kvm/vgic/vgic-v2.c
@@ -108,11 +108,22 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
* If this causes us to lower the level, we have to also clear
* the physical active state, since we will otherwise never be
* told when the interrupt becomes asserted again.
+ *
+ * Another case is when the interrupt requires a helping hand
+ * on deactivation (no HW deactivation, for example).
*/
- if (vgic_irq_is_mapped_level(irq) && (val & GICH_LR_PENDING_BIT)) {
- irq->line_level = vgic_get_phys_line_level(irq);
+ if (vgic_irq_is_mapped_level(irq)) {
+ bool resample = false;
+
+ if (val & GICH_LR_PENDING_BIT) {
+ irq->line_level = vgic_get_phys_line_level(irq);
+ resample = !irq->line_level;
+ } else if (vgic_irq_needs_resampling(irq) &&
+ !(irq->active || irq->pending_latch)) {
+ resample = true;
+ }

- if (!irq->line_level)
+ if (resample)
vgic_irq_set_phys_active(irq, false);
}

@@ -152,7 +163,7 @@ void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
if (irq->group)
val |= GICH_LR_GROUP1;

- if (irq->hw) {
+ if (irq->hw && !vgic_irq_needs_resampling(irq)) {
val |= GICH_LR_HW;
val |= irq->hwintid << GICH_LR_PHYSID_CPUID_SHIFT;
/*
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 41ecf219c333..66004f61cd83 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -101,11 +101,22 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
* If this causes us to lower the level, we have to also clear
* the physical active state, since we will otherwise never be
* told when the interrupt becomes asserted again.
+ *
+ * Another case is when the interrupt requires a helping hand
+ * on deactivation (no HW deactivation, for example).
*/
- if (vgic_irq_is_mapped_level(irq) && (val & ICH_LR_PENDING_BIT)) {
- irq->line_level = vgic_get_phys_line_level(irq);
+ if (vgic_irq_is_mapped_level(irq)) {
+ bool resample = false;
+
+ if (val & ICH_LR_PENDING_BIT) {
+ irq->line_level = vgic_get_phys_line_level(irq);
+ resample = !irq->line_level;
+ } else if (vgic_irq_needs_resampling(irq) &&
+ !(irq->active || irq->pending_latch)) {
+ resample = true;
+ }

- if (!irq->line_level)
+ if (resample)
vgic_irq_set_phys_active(irq, false);
}

@@ -136,7 +147,7 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
}
}

- if (irq->hw) {
+ if (irq->hw && !vgic_irq_needs_resampling(irq)) {
val |= ICH_LR_HW;
val |= ((u64)irq->hwintid) << ICH_LR_PHYS_ID_SHIFT;
/*
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index e5f06df000f2..e602d848fc1a 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -99,6 +99,11 @@ enum vgic_irq_config {
* kvm_arm_get_running_vcpu() to get the vcpu pointer for private IRQs.
*/
struct irq_ops {
+ /* Per interrupt flags for special-cased interrupts */
+ unsigned long flags;
+
+#define VGIC_IRQ_SW_RESAMPLE BIT(0) /* Clear the active state for resampling */
+
/*
* Callback function pointer to in-kernel devices that can tell us the
* state of the input level of mapped level-triggered IRQ faster than
@@ -150,6 +155,11 @@ struct vgic_irq {
for in-kernel devices. */
};

+static inline bool vgic_irq_needs_resampling(struct vgic_irq *irq)
+{
+ return irq->ops && (irq->ops->flags & VGIC_IRQ_SW_RESAMPLE);
+}
+
struct vgic_register_region;
struct vgic_its;

--
2.30.2