[Xen-devel] [PATCH v5 p1 10/14] xen/arm: route_irq_to_guest: Check validity of the IRQ

[Julien Grall <julien.grall@xxxxxxxxxx>]

From: Julien Grall <julien.grall@xxxxxxxxxx>

Currently Xen only supports SPIs routing for guest, add a function
is_assignable_irq to check if we can assign a given IRQ to the guest.

Secondly, make sure the vIRQ is not the greater than the number of IRQs
configured in the vGIC and it's an SPI.

Thirdly, when the IRQ is already assigned to the domain, check the user
is not asking to use a different vIRQ than the one already bound.

Finally, desc->arch.type which contains the IRQ type (i.e level/edge) must
be correctly configured before. The misconfiguration can happen when:
    - the device has been blacklisted for the current platform
    - the IRQ has not been described in the device tree

Also, use XENLOG_G_ERR in the error message within the function as it will
be later called from a guest.

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

---
    Changes in v5:
        - Typoe in the commit message
        - Add Ian and Stefano's ack

    Changes in v4:
        - Use NR_LOCAL_IRQS rather than 32
        - Move the check to the IRQ and irq_to_desc after the vIRQ check
        - Typoes and rewording the commit message and in the patch
        - Use printk rather than dprintk.

    Changes in v3:
        - Fix typo in commit message and comment
        - Add a check that the vIRQ is an SPI
        - Check if the user is not asking for a different vIRQ when the
        IRQ is already assigned to the guest

    Changes in v2:
        - Rename is_routable_irq into is_assignable_irq
        - Check if the IRQ is not greater than the number handled by the
        number of IRQs handled by the gic
        - Move is_assignable_irq in irq.c rather than defining in the
        header irq.h
        - Retrieve the irq descriptor after checking the validity of the
        IRQ
        - vgic_num_irqs has been moved in a separate patch
        - Fix the irq check against vgic_num_irqs
        - Use virq instead of irq for vGIC sanity check
---
 xen/arch/arm/irq.c        | 59 +++++++++++++++++++++++++++++++++++++++++++----
 xen/include/asm-arm/irq.h |  2 ++
 2 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index beb746a..4c3e381 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -387,6 +387,16 @@ err:
     return rc;
 }
 
+bool_t is_assignable_irq(unsigned int irq)
+{
+    /* For now, we can only route SPIs to the guest */
+    return ((irq >= NR_LOCAL_IRQS) && (irq < gic_number_lines()));
+}
+
+/*
+ * Route an IRQ to a specific guest.
+ * For now only SPIs are assignable to the guest.
+ */
 int route_irq_to_guest(struct domain *d, unsigned int virq,
                        unsigned int irq, const char * devname)
 {
@@ -396,6 +406,28 @@ int route_irq_to_guest(struct domain *d, unsigned int virq,
     unsigned long flags;
     int retval = 0;
 
+    if ( virq >= vgic_num_irqs(d) )
+    {
+        printk(XENLOG_G_ERR
+               "the vIRQ number %u is too high for domain %u (max = %u)\n",
+               irq, d->domain_id, vgic_num_irqs(d));
+        return -EINVAL;
+    }
+
+    /* Only routing to virtual SPIs is supported */
+    if ( virq < NR_LOCAL_IRQS )
+    {
+        printk(XENLOG_G_ERR "IRQ can only be routed to an SPI");
+        return -EINVAL;
+    }
+
+    if ( !is_assignable_irq(irq) )
+    {
+        printk(XENLOG_G_ERR "the IRQ%u is not routable\n", irq);
+        return -EINVAL;
+    }
+    desc = irq_to_desc(irq);
+
     action = xmalloc(struct irqaction);
     if ( !action )
         return -ENOMEM;
@@ -416,8 +448,18 @@ int route_irq_to_guest(struct domain *d, unsigned int virq,
 
     spin_lock_irqsave(&desc->lock, flags);
 
-    /* If the IRQ is already used by someone
-     *  - If it's the same domain -> Xen doesn't need to update the IRQ desc
+    if ( desc->arch.type == DT_IRQ_TYPE_INVALID )
+    {
+        printk(XENLOG_G_ERR "IRQ %u has not been configured\n", irq);
+        retval = -EIO;
+        goto out;
+    }
+
+    /*
+     * If the IRQ is already used by someone
+     *  - If it's the same domain -> Xen doesn't need to update the IRQ desc.
+     *  For safety check if we are not trying to assign the IRQ to a
+     *  different vIRQ.
      *  - Otherwise -> For now, don't allow the IRQ to be shared between
      *  Xen and domains.
      */
@@ -426,13 +468,22 @@ int route_irq_to_guest(struct domain *d, unsigned int 
virq,
         struct domain *ad = irq_get_domain(desc);
 
         if ( test_bit(_IRQ_GUEST, &desc->status) && d == ad )
+        {
+            if ( irq_get_guest_info(desc)->virq != virq )
+            {
+                printk(XENLOG_G_ERR
+                       "d%u: IRQ %u is already assigned to vIRQ %u\n",
+                       d->domain_id, irq, irq_get_guest_info(desc)->virq);
+                retval = -EBUSY;
+            }
             goto out;
+        }
 
         if ( test_bit(_IRQ_GUEST, &desc->status) )
-            printk(XENLOG_ERR "ERROR: IRQ %u is already used by domain %u\n",
+            printk(XENLOG_G_ERR "IRQ %u is already used by domain %u\n",
                    irq, ad->domain_id);
         else
-            printk(XENLOG_ERR "ERROR: IRQ %u is already used by Xen\n", irq);
+            printk(XENLOG_G_ERR "IRQ %u is already used by Xen\n", irq);
         retval = -EBUSY;
         goto out;
     }
diff --git a/xen/include/asm-arm/irq.h b/xen/include/asm-arm/irq.h
index f00eb11..71b39e7 100644
--- a/xen/include/asm-arm/irq.h
+++ b/xen/include/asm-arm/irq.h
@@ -37,6 +37,8 @@ void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, int 
is_fiq);
 
 #define domain_pirq_to_irq(d, pirq) (pirq)
 
+bool_t is_assignable_irq(unsigned int irq);
+
 void init_IRQ(void);
 void init_secondary_IRQ(void);
 
-- 
2.1.4


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