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[Xen-changelog] [xen-4.1-testing] Clear IRQ_GUEST in irq_desc->status when setting action to NULL.

# HG changeset patch
# User Igor Mammedov <imammedo@xxxxxxxxxx>
# Date 1317655792 -3600
# Node ID 2a0cd93f7ed9666ac60baa19c69bd89cad63c79e
# Parent  5c395e993fe4064f0e3e13af70af9e440dc00689
Clear IRQ_GUEST in irq_desc->status when setting action to NULL.

Looking more closely at usage of action field with relation to
IRQ_GUEST flag. It appears that set IRQ_GUEST implies that action
is not NULL. As result it is not safe to set action to NULL and
leave IRQ_GUEST set.

Hence IRQ_GUEST should be cleared in dynamic_irq_cleanup where
action is set to NULL.

An addition remove BUGON at __pirq_guest_unbind that appears to be
bogus and not needed anymore.

Thanks Paolo Bonzini for NACKing previous patch, and pointing at the
correct solution.

Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>

Reinstate the BUG_ON, but after the action==NULL check. Since we then
go and start interpreting action as an irq_guest_action_t, the BUG_ON
is relevant here.

More generally, the brute-force nature of dynamic_irq_cleanup() looks
a bit worrying. Possibly there should be more integratioin with
pirq_guest_unbind() logic, for cleaning up un-acked EOIs and the like.

Signed-off-by: Keir Fraser <keir@xxxxxxx>
xen-unstable changeset:   23852:c944e82bb092
xen-unstable date:        Sun Sep 18 00:00:26 2011 +0100

diff -r 5c395e993fe4 -r 2a0cd93f7ed9 xen/arch/x86/irq.c
--- a/xen/arch/x86/irq.c        Tue Sep 27 17:27:17 2011 +0100
+++ b/xen/arch/x86/irq.c        Mon Oct 03 16:29:52 2011 +0100
@@ -152,6 +152,7 @@
     spin_lock_irqsave(&desc->lock, flags);
     desc->status  |= IRQ_DISABLED;
+    desc->status  &= ~IRQ_GUEST;
     action = desc->action;
     desc->action  = NULL;
@@ -1288,8 +1289,6 @@
     cpumask_t           cpu_eoi_map;
     int                 i;
-    BUG_ON(!(desc->status & IRQ_GUEST));
     action = (irq_guest_action_t *)desc->action;
     irq = desc - irq_desc;
@@ -1300,6 +1299,8 @@
         return NULL;
+    BUG_ON(!(desc->status & IRQ_GUEST));
     for ( i = 0; (i < action->nr_guests) && (action->guest[i] != d); i++ )
     BUG_ON(i == action->nr_guests);

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