[Xen-devel] [PATCH v5 p2 03/19] xen/arm: Release IRQ routed to a domain when it's destroying

[Julien Grall <julien.grall@xxxxxxxxxx>]

From: Julien Grall <julien.grall@xxxxxxxxxx>

Xen has to release IRQ routed to a domain in order to reuse later.
Currently only SPIs can be routed to the guest so we only need to
browse SPIs for a specific domain.

Furthermore, a guest can crash and leave the IRQ in an incorrect state
(i.e has not been EOIed). Xen will have to reset the IRQ in order to
be able to reuse the IRQ later.

Introduce 2 new functions for release an IRQ routed to a domain:
    - release_guest_irq: upper level to retrieve the IRQ, call the GIC
    code and release the action
    - gic_remove_guest_irq: Check if we can remove the IRQ, and reset
    it if necessary

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

---
    Changes in v5:
        - Typoes in the commit message
        - Add Ian's Ack

    Changes in v4:
        - Reorder the code flow
        - Typoes and coding style
        - Use the newly helper spi_to_pending

    Changes in v3:
        - Take the vgic rank lock to protect p->desc
        - Correctly check if the IRQ is disabled
        - Extend the check on the virq in release_guest_irq
        - Use vgic_get_target_vcpu to get the target vCPU
        - Remove spurious change

    Changes in v2:
        - Drop the desc->handler = &no_irq_type in release_irq as it's
        buggy if the IRQ is routed to Xen
        - Add release_guest_irq and gic_remove_guest_irq
---
 xen/arch/arm/gic.c        | 45 +++++++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/irq.c        | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/vgic.c       | 16 ++++++++++++++++
 xen/include/asm-arm/gic.h |  4 ++++
 xen/include/asm-arm/irq.h |  2 ++
 5 files changed, 113 insertions(+)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 5f34997..f023e4f 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -163,6 +163,51 @@ out:
     return res;
 }
 
+/* This function only works with SPIs for now */
+int gic_remove_irq_from_guest(struct domain *d, unsigned int virq,
+                              struct irq_desc *desc)
+{
+    struct vcpu *v_target = vgic_get_target_vcpu(d->vcpu[0], virq);
+    struct vgic_irq_rank *rank = vgic_rank_irq(v_target, virq);
+    struct pending_irq *p = irq_to_pending(v_target, virq);
+    unsigned long flags;
+
+    ASSERT(spin_is_locked(&desc->lock));
+    ASSERT(test_bit(_IRQ_GUEST, &desc->status));
+    ASSERT(p->desc == desc);
+
+    vgic_lock_rank(v_target, rank, flags);
+
+    if ( d->is_dying )
+    {
+        desc->handler->shutdown(desc);
+
+        /* EOI the IRQ it it has not been done by the guest */
+        if ( test_bit(_IRQ_INPROGRESS, &desc->status) )
+            gic_hw_ops->deactivate_irq(desc);
+        clear_bit(_IRQ_INPROGRESS, &desc->status);
+    }
+    else
+    {
+        /*
+         * TODO: Handle eviction from LRs For now, deny
+         * remove if the IRQ is inflight or not disabled.
+         */
+        if ( test_bit(_IRQ_INPROGRESS, &desc->status) ||
+             !test_bit(_IRQ_DISABLED, &desc->status) )
+            return -EBUSY;
+    }
+
+    clear_bit(_IRQ_GUEST, &desc->status);
+    desc->handler = &no_irq_type;
+
+    p->desc = NULL;
+
+    vgic_unlock_rank(v_target, rank, flags);
+
+    return 0;
+}
+
 int gic_irq_xlate(const u32 *intspec, unsigned int intsize,
                   unsigned int *out_hwirq,
                   unsigned int *out_type)
diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index b2ddf6b..376c9f2 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -513,6 +513,52 @@ free_info:
     return retval;
 }
 
+int release_guest_irq(struct domain *d, unsigned int virq)
+{
+    struct irq_desc *desc;
+    struct irq_guest *info;
+    unsigned long flags;
+    struct pending_irq *p;
+    int ret;
+
+    /* Only SPIs are supported */
+    if ( virq < NR_LOCAL_IRQS || virq >= vgic_num_irqs(d) )
+        return -EINVAL;
+
+    p = spi_to_pending(d, virq);
+    if ( !p->desc )
+        return -EINVAL;
+
+    desc = p->desc;
+
+    spin_lock_irqsave(&desc->lock, flags);
+
+    ret = -EINVAL;
+    if ( !test_bit(_IRQ_GUEST, &desc->status) )
+        goto unlock;
+
+    info = irq_get_guest_info(desc);
+    ret = -EINVAL;
+    if ( d != info->d )
+        goto unlock;
+
+    ret = gic_remove_irq_from_guest(d, virq, desc);
+    if ( ret )
+        goto unlock;
+
+    spin_unlock_irqrestore(&desc->lock, flags);
+
+    release_irq(desc->irq, info);
+    xfree(info);
+
+    return 0;
+
+unlock:
+    spin_unlock_irqrestore(&desc->lock, flags);
+
+    return ret;
+}
+
 /*
  * pirq event channels. We don't use these on ARM, instead we use the
  * features of the GIC to inject virtualised normal interrupts.
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 55c8927..05c5010 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -135,6 +135,22 @@ void register_vgic_ops(struct domain *d, const struct 
vgic_ops *ops)
 
 void domain_vgic_free(struct domain *d)
 {
+    int i;
+    int ret;
+
+    for ( i = 0; i < (d->arch.vgic.nr_spis); i++ )
+    {
+        struct pending_irq *p = spi_to_pending(d, i + 32);
+
+        if ( p->desc )
+        {
+            ret = release_guest_irq(d, p->irq);
+            if ( ret )
+                dprintk(XENLOG_G_WARNING, "d%u: Failed to release virq %u ret 
= %d\n",
+                        d->domain_id, p->irq, ret);
+        }
+    }
+
     xfree(d->arch.vgic.shared_irqs);
     xfree(d->arch.vgic.pending_irqs);
     xfree(d->arch.vgic.allocated_irqs);
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index ef4bf9a..9e2acb7 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -220,6 +220,10 @@ extern int gic_route_irq_to_guest(struct domain *, 
unsigned int virq,
                                   struct irq_desc *desc,
                                   unsigned int priority);
 
+/* Remove an IRQ passthrough to a guest */
+int gic_remove_irq_from_guest(struct domain *d, unsigned int virq,
+                              struct irq_desc *desc);
+
 extern void gic_inject(void);
 extern void gic_clear_pending_irqs(struct vcpu *v);
 extern int gic_events_need_delivery(void);
diff --git a/xen/include/asm-arm/irq.h b/xen/include/asm-arm/irq.h
index 71b39e7..34b492b 100644
--- a/xen/include/asm-arm/irq.h
+++ b/xen/include/asm-arm/irq.h
@@ -44,6 +44,8 @@ void init_secondary_IRQ(void);
 
 int route_irq_to_guest(struct domain *d, unsigned int virq,
                        unsigned int irq, const char *devname);
+int release_guest_irq(struct domain *d, unsigned int irq);
+
 void arch_move_irqs(struct vcpu *v);
 
 /* Set IRQ type for an SPI */
-- 
2.1.4


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