x86/dpci: do not remove pirqs from domain tree on unbind

A fix for a previous issue removed the pirqs from the domain tree when
they are unbound in order to prevent shared pirqs from triggering a
BUG_ON in __pirq_guest_unbind if they are unbound multiple times. That
caused free_domain_pirqs to no longer unmap the pirqs because they
are gone from the domain pirq tree, thus leaving stale unbound pirqs
after domain destruction if the domain had mapped dpci pirqs after
shutdown.

Take a different approach to fix the original issue, instead of
removing the pirq from d->pirq_tree clear the flags of the dpci pirq
struct to signal that the pirq is now unbound. This prevents calling
pirq_guest_unbind multiple times for the same pirq without having to
remove it from the domain pirq tree.

This is XSA-360.

Fixes: 5b58dad089 ('x86/pass-through: avoid double IRQ unbind during domain cleanup')
Reported-by: Samuel Verschelde <samuel.verschelde@vates.fr>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: 58427889f5a420cc5226f88524b3228f90b72a58
master date: 2021-01-21 16:11:41 +0100

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 37c86283ccbb0830742c140022c83596b6302387..41800e10834dd04a7341f2e345c20509aae7bb81 100644 (file)
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1331,7 +1331,7 @@ void (pirq_cleanup_check)(struct pirq *pirq, struct domain *d)
     }
 
     if ( radix_tree_delete(&d->pirq_tree, pirq->pirq) != pirq )
-        BUG_ON(!d->is_dying);
+        BUG();
 }
 
 /* Flush all ready EOIs from the top of this CPU's pending-EOI stack. */

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 2d6238a5bb51eca827333a6f27859a8fe841cfcc..418b2cdf049c840f45fda5991dedd578e1932c17 100644 (file)
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -862,6 +862,10 @@ static int pci_clean_dpci_irq(struct domain *d,
 {
     struct dev_intx_gsi_link *digl, *tmp;
 
+    if ( !pirq_dpci->flags )
+        /* Already processed. */
+        return 0;
+
     pirq_guest_unbind(d, dpci_pirq(pirq_dpci));
 
     if ( pt_irq_need_timer(pirq_dpci->flags) )
@@ -872,15 +876,10 @@ static int pci_clean_dpci_irq(struct domain *d,
         list_del(&digl->list);
         xfree(digl);
     }
+    /* Note the pirq is now unbound. */
+    pirq_dpci->flags = 0;
 
-    radix_tree_delete(&d->pirq_tree, dpci_pirq(pirq_dpci)->pirq);
-
-    if ( !pt_pirq_softirq_active(pirq_dpci) )
-        return 0;
-
-    domain_get_irq_dpci(d)->pending_pirq_dpci = pirq_dpci;
-
-    return -ERESTART;
+    return pt_pirq_softirq_active(pirq_dpci) ? -ERESTART : 0;
 }
 
 static int pci_clean_dpci_irqs(struct domain *d)
@@ -897,18 +896,8 @@ static int pci_clean_dpci_irqs(struct domain *d)
     hvm_irq_dpci = domain_get_irq_dpci(d);
     if ( hvm_irq_dpci != NULL )
     {
-        int ret = 0;
-
-        if ( hvm_irq_dpci->pending_pirq_dpci )
-        {
-            if ( pt_pirq_softirq_active(hvm_irq_dpci->pending_pirq_dpci) )
-                 ret = -ERESTART;
-            else
-                 hvm_irq_dpci->pending_pirq_dpci = NULL;
-        }
+        int ret = pt_pirq_iterate(d, pci_clean_dpci_irq, NULL);
 
-        if ( !ret )
-            ret = pt_pirq_iterate(d, pci_clean_dpci_irq, NULL);
         if ( ret )
         {
             spin_unlock(&d->event_lock);

diff --git a/xen/include/asm-x86/hvm/irq.h b/xen/include/asm-x86/hvm/irq.h
index 532880d497e6d9d67c85b79246f6f69d2fced4b8..7f76f6c4378e176146b113ac15f6f682c74dbb02 100644 (file)
--- a/xen/include/asm-x86/hvm/irq.h
+++ b/xen/include/asm-x86/hvm/irq.h
@@ -160,8 +160,6 @@ struct hvm_irq_dpci {
     DECLARE_BITMAP(isairq_map, NR_ISAIRQS);
     /* Record of mapped Links */
     uint8_t link_cnt[NR_LINK];
-    /* Clean up: Entry with a softirq invocation pending / in progress. */
-    struct hvm_pirq_dpci *pending_pirq_dpci;
 };
 
 /* Machine IRQ to guest device/intx mapping. */