[Xen-changelog] [xen stable-4.4] x86/IO-APIC: don't create pIRQ mapping from masked RTE

[patchbot@xxxxxxx]

commit 9a00f96bb09ff8642bef2a3edde855a924093614
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Sep 10 15:51:56 2015 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Sep 10 15:51:56 2015 +0200

    x86/IO-APIC: don't create pIRQ mapping from masked RTE
    
    While moving our XenoLinux patches to 4.2-rc I noticed bogus "already
    mapped" messages resulting from Linux (legitimately) writing RTEs with
    only the mask bit set. Clearly we shouldn't even attempt to create a
    pIRQ <-> IRQ mapping from such RTEs.
    
    In the course of this I also found that the respective message isn't
    really useful without also printing the pre-existing mapping. And I
    noticed that map_domain_pirq() allowed IRQ0 to get through, despite us
    never allowing a domain to control that interrupt.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 669d4b85c433674ab3b52ef707af0d3a551c941f
    master date: 2015-08-25 16:18:31 +0200
---
 xen/arch/x86/io_apic.c |   25 ++++++++++++++++---------
 xen/arch/x86/irq.c     |    7 ++++---
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 8f41a06..3ab29b0 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2370,9 +2370,14 @@ int ioapic_guest_write(unsigned long physbase, unsigned 
int reg, u32 val)
      * pirq and irq mapping. Where the GSI is greater than 256, we assume
      * that dom0 pirq == irq.
      */
-    pirq = (irq >= 256) ? irq : rte.vector;
-    if ( (pirq < 0) || (pirq >= dom0->nr_pirqs) )
-        return -EINVAL;
+    if ( !rte.mask )
+    {
+        pirq = (irq >= 256) ? irq : rte.vector;
+        if ( pirq >= dom0->nr_pirqs )
+            return -EINVAL;
+    }
+    else
+        pirq = -1;
     
     if ( desc->action )
     {
@@ -2407,12 +2412,14 @@ int ioapic_guest_write(unsigned long physbase, unsigned 
int reg, u32 val)
 
         printk(XENLOG_INFO "allocated vector %02x for irq %d\n", ret, irq);
     }
-    spin_lock(&dom0->event_lock);
-    ret = map_domain_pirq(dom0, pirq, irq,
-            MAP_PIRQ_TYPE_GSI, NULL);
-    spin_unlock(&dom0->event_lock);
-    if ( ret < 0 )
-        return ret;
+    if ( pirq >= 0 )
+    {
+        spin_lock(&dom0->event_lock);
+        ret = map_domain_pirq(dom0, pirq, irq, MAP_PIRQ_TYPE_GSI, NULL);
+        spin_unlock(&dom0->event_lock);
+        if ( ret < 0 )
+            return ret;
+    }
 
     spin_lock_irqsave(&ioapic_lock, flags);
     /* Set the correct irq-handling type. */
diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 194d508..77aded7 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1897,7 +1897,7 @@ int map_domain_pirq(
     if ( !irq_access_permitted(current->domain, irq))
         return -EPERM;
 
-    if ( pirq < 0 || pirq >= d->nr_pirqs || irq < 0 || irq >= nr_irqs )
+    if ( pirq < 0 || pirq >= d->nr_pirqs || irq <= 0 || irq >= nr_irqs )
     {
         dprintk(XENLOG_G_ERR, "dom%d: invalid pirq %d or irq %d\n",
                 d->domain_id, pirq, irq);
@@ -1910,8 +1910,9 @@ int map_domain_pirq(
     if ( (old_irq > 0 && (old_irq != irq) ) ||
          (old_pirq && (old_pirq != pirq)) )
     {
-        dprintk(XENLOG_G_WARNING, "dom%d: pirq %d or irq %d already mapped\n",
-                d->domain_id, pirq, irq);
+        dprintk(XENLOG_G_WARNING,
+                "dom%d: pirq %d or irq %d already mapped (%d,%d)\n",
+                d->domain_id, pirq, irq, old_pirq, old_irq);
         return 0;
     }
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.4

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