[Xen-devel] [PATCH v3 09/24] xen/arm: route_irq_to_guest: Check validity of the IRQ

[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 that the number of IRQs handle
to the vGIC and it's an SPIs.

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 IRQ type won't be configure when:
    - the device has been blacklist for the current platform
    - the IRQ has not been describe in the device tree

I think we can safely assume that a user won't never ask to route
as such IRQ to the guest.

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>

---
    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        | 58 +++++++++++++++++++++++++++++++++++++++++++----
 xen/include/asm-arm/irq.h |  2 ++
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index 830832c..af408ac 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -379,6 +379,15 @@ 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 assignabled to the guest.
+ */
 int route_irq_to_guest(struct domain *d, unsigned int virq,
                        unsigned int irq, const char * devname)
 {
@@ -388,6 +397,29 @@ int route_irq_to_guest(struct domain *d, unsigned int virq,
     unsigned long flags;
     int retval = 0;
 
+    if ( !is_assignable_irq(irq) )
+    {
+        dprintk(XENLOG_G_ERR, "the IRQ%u is not routable\n", irq);
+        return -EINVAL;
+    }
+
+    desc = irq_to_desc(irq);
+
+    if ( virq >= vgic_num_irqs(d) )
+    {
+        dprintk(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 < 32 )
+    {
+        dprintk(XENLOG_G_ERR, "IRQ can only be routed to a virtual SPIs");
+        return -EINVAL;
+    }
+
     action = xmalloc(struct irqaction);
     if ( !action )
         return -ENOMEM;
@@ -408,8 +440,18 @@ int route_irq_to_guest(struct domain *d, unsigned int virq,
 
     spin_lock_irqsave(&desc->lock, flags);
 
+    if ( desc->arch.type == DT_IRQ_TYPE_INVALID )
+    {
+        dprintk(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
+     *  - 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.
      */
@@ -418,13 +460,21 @@ 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 )
+            {
+                dprintk(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 = -EPERM;
+            }
             goto out;
+        }
 
         if ( test_bit(_IRQ_GUEST, &desc->status) )
-            printk(XENLOG_ERR "ERROR: IRQ %u is already used by domain %u\n",
-                   irq, ad->domain_id);
+            dprintk(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);
+            dprintk(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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