[Xen-devel] [PATCH][RFC] pv-ops: fix shared irq device passthrough

["Han, Weidong" <weidong.han@xxxxxxxxx>]

>From 9c91f23076c555690488cbd81f889f279d4cf2fa Mon Sep 17 00:00:00 2001
From: Weidong Han <weidong.han@xxxxxxxxx>
Date: Sat, 24 Oct 2009 03:18:30 +0800
Subject: [PATCH] pv-ops: fix shared irq device passthrough

In driver/xen/events.c, whether bind_pirq is shareable or not is
determined by desc->action is NULL or not. But in __setup_irq,
startup(irq) is invoked before desc->action is assigned with
new action. So desc->action in startup_irq is alwasy NULL, and
bind_pirq is always not shareable. This results in pt_irq_create_bind
failure when passthrough a device which shares irq to other devices.

This patch move desc->action before startup(irq), therefore fix
the problem.

Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>
---
 kernel/irq/manage.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 07a11dc..3b85b72 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -565,6 +565,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct 
irqaction *new)
 {
        struct irqaction *old, **old_ptr;
        const char *old_name = NULL;
+       int old_irq;
        unsigned long flags;
        int shared = 0;
        int ret;
@@ -644,6 +645,11 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, 
struct irqaction *new)
                shared = 1;
        }
 
+       old = *old_ptr;
+       old_irq = new->irq;
+       new->irq = irq;
+       *old_ptr = new;
+
        if (!shared) {
                irq_chip_set_defaults(desc->chip);
 
@@ -654,8 +660,11 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, 
struct irqaction *new)
                        ret = __irq_set_trigger(desc, irq,
                                        new->flags & IRQF_TRIGGER_MASK);
 
-                       if (ret)
+                       if (ret) {
+                               new->irq = old_irq;
+                               *old_ptr = old;
                                goto out_thread;
+                       }
                } else
                        compat_irq_chip_set_default_handler(desc);
 #if defined(CONFIG_IRQ_PER_CPU)
@@ -690,9 +699,6 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct 
irqaction *new)
                                (int)(new->flags & IRQF_TRIGGER_MASK));
        }
 
-       new->irq = irq;
-       *old_ptr = new;
-
        /* Reset broken irq detection when installing new handler */
        desc->irq_count = 0;
        desc->irqs_unhandled = 0;
-- 
1.6.0.4

Attachment: 0001-pv-ops-fix-shared-irq-device-passthrough.patch
Description: 0001-pv-ops-fix-shared-irq-device-passthrough.patch

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