[Xen-devel] [PATCH v5 5/6] xen/arm: Only enable physical IRQs when the guest asks

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

From: Julien Grall <julien.grall@xxxxxxxxxx>

Set/Unset IRQ_DISABLED from gic_irq_enable and gic_irq_disable.
Enable IRQs when the guest requests it, not unconditionally at boot time.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

---
Changes in v2:
- protect startup and shutdown with gic and desc locks.

Changes in v4:
- disable interrupts in gic_irq_enable;
- clear IRQ_DISABLED and dsb() before writing to the GICD register.
---
 xen/arch/arm/gic.c  |   48 ++++++++++++++++++++++++++++--------------------
 xen/arch/arm/vgic.c |    6 ++----
 2 files changed, 30 insertions(+), 24 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index b2caced..ff83426 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -132,17 +132,29 @@ void gic_restore_state(struct vcpu *v)
 static void gic_irq_enable(struct irq_desc *desc)
 {
     int irq = desc->irq;
+    unsigned long flags;
 
+    spin_lock_irqsave(&desc->lock, flags);
+    spin_lock(&gic.lock);
+    desc->status &= ~IRQ_DISABLED;
+    dsb();
     /* Enable routing */
     GICD[GICD_ISENABLER + irq / 32] = (1u << (irq % 32));
+    spin_unlock(&gic.lock);
+    spin_unlock_irqrestore(&desc->lock, flags);
 }
 
 static void gic_irq_disable(struct irq_desc *desc)
 {
     int irq = desc->irq;
 
+    spin_lock(&desc->lock);
+    spin_lock(&gic.lock);
     /* Disable routing */
     GICD[GICD_ICENABLER + irq / 32] = (1u << (irq % 32));
+    desc->status |= IRQ_DISABLED;
+    spin_unlock(&gic.lock);
+    spin_unlock(&desc->lock);
 }
 
 static unsigned int gic_irq_startup(struct irq_desc *desc)
@@ -247,24 +259,20 @@ static int gic_route_irq(unsigned int irq, bool_t level,
     ASSERT(priority <= 0xff);     /* Only 8 bits of priority */
     ASSERT(irq < gic.lines);      /* Can't route interrupts that don't exist */
 
-    spin_lock_irqsave(&desc->lock, flags);
-    spin_lock(&gic.lock);
-
     if ( desc->action != NULL )
-    {
-        spin_unlock(&gic.lock);
-        spin_unlock(&desc->lock);
         return -EBUSY;
-    }
-
-    desc->handler = &gic_host_irq_type;
 
     /* Disable interrupt */
     desc->handler->shutdown(desc);
 
-    gic_set_irq_properties(irq, level, cpu_mask, priority);
+    spin_lock_irqsave(&desc->lock, flags);
+
+    desc->handler = &gic_host_irq_type;
 
+    spin_lock(&gic.lock);
+    gic_set_irq_properties(irq, level, cpu_mask, priority);
     spin_unlock(&gic.lock);
+
     spin_unlock_irqrestore(&desc->lock, flags);
     return 0;
 }
@@ -557,16 +565,13 @@ void __init release_irq(unsigned int irq)
 
     desc = irq_to_desc(irq);
 
+    desc->handler->shutdown(desc);
+
     spin_lock_irqsave(&desc->lock,flags);
     action = desc->action;
     desc->action  = NULL;
-    desc->status |= IRQ_DISABLED;
     desc->status &= ~IRQ_GUEST;
 
-    spin_lock(&gic.lock);
-    desc->handler->shutdown(desc);
-    spin_unlock(&gic.lock);
-
     spin_unlock_irqrestore(&desc->lock,flags);
 
     /* Wait to make sure it's not being used on another CPU */
@@ -583,11 +588,8 @@ static int __setup_irq(struct irq_desc *desc, unsigned int 
irq,
         return -EBUSY;
 
     desc->action  = new;
-    desc->status &= ~IRQ_DISABLED;
     dsb();
 
-    desc->handler->startup(desc);
-
     return 0;
 }
 
@@ -600,11 +602,12 @@ int __init setup_dt_irq(const struct dt_irq *irq, struct 
irqaction *new)
     desc = irq_to_desc(irq->irq);
 
     spin_lock_irqsave(&desc->lock, flags);
-
     rc = __setup_irq(desc, irq->irq, new);
-
     spin_unlock_irqrestore(&desc->lock, flags);
 
+    desc->handler->startup(desc);
+
+
     return rc;
 }
 
@@ -745,6 +748,7 @@ int gic_route_irq_to_guest(struct domain *d, const struct 
dt_irq *irq,
     unsigned long flags;
     int retval;
     bool_t level;
+    struct pending_irq *p;
 
     action = xmalloc(struct irqaction);
     if (!action)
@@ -771,6 +775,10 @@ int gic_route_irq_to_guest(struct domain *d, const struct 
dt_irq *irq,
         goto out;
     }
 
+    /* TODO: do not assume delivery to vcpu0 */
+    p = irq_to_pending(d->vcpu[0], irq->irq);
+    p->desc = desc;
+
 out:
     spin_unlock(&gic.lock);
     spin_unlock_irqrestore(&desc->lock, flags);
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index f2f1702..ad17d1d 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -372,6 +372,8 @@ static void vgic_enable_irqs(struct vcpu *v, uint32_t r, 
int n)
         set_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
         if ( !list_empty(&p->inflight) && !test_bit(GIC_IRQ_GUEST_VISIBLE, 
&p->status) )
             gic_set_guest_irq(v, irq, GICH_LR_PENDING, p->priority);
+        if ( p->desc != NULL )
+            p->desc->handler->enable(p->desc);
         i++;
     }
 }
@@ -694,10 +696,6 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int 
irq, int virtual)
     n->irq = irq;
     set_bit(GIC_IRQ_GUEST_PENDING, &n->status);
     n->priority = priority;
-    if (!virtual)
-        n->desc = irq_to_desc(irq);
-    else
-        n->desc = NULL;
 
     /* the irq is enabled */
     if ( test_bit(GIC_IRQ_GUEST_ENABLED, &n->status) )
-- 
1.7.10.4


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