Xen devel - Feb 2012 - [PATCH] x86/mm: Make sure the event channel is released accurately

# HG changeset patch
# User h00166998@h00166998.china.huawei.com
# Date 1329462865 -28800
# Node ID 9fd12f919ddbd15927117eff42149664dba698ca
# Parent  b75664e5390583c5d2075c82a14245bc941b3aaf
x86/mm: Make sure the event channel is released accurately

    In xenpaging source code,there is an interdomain communication between dom0
and domU. In mem_event_enable(),the function alloc_unbound_xen_event_channel()
allocates a free port for domU, and then it will be bound with dom0.
When xenpaging tears down,it just frees dom0''s event channel port by
xc_evtchn_unbind(), leaves domU''s port still occupied.
    So we add the patch to free domU''s port when xenpaging exits.
We need double free interdomain eventchannel. First free domainU port,
and leave domain 0 port unbond, Then free domain 0 port.

Signed-off-byKaixing Hong <hongkaixing@huawei.com>,
Signed-off-byZhen Shi <bicky.shi@huawei.com>

diff -r b75664e53905 -r 9fd12f919ddb xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c	Thu Feb 16 15:43:02 2012 +0000
+++ b/xen/arch/x86/mm/mem_event.c	Fri Feb 17 15:14:25 2012 +0800
@@ -243,6 +243,9 @@
             return -EBUSY;
         }
 
+        /* Free domU''s event channel and leave the other one unbound
*/
+        free_xen_event_channel(d->vcpu[0], med->xen_port);
+        
         unmap_domain_page(med->ring_page);
         med->ring_page = NULL;
 


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On Fri, Feb 17, hongkaixing@huawei.com wrote:
>     In xenpaging source code,there is an interdomain communication between
dom0
> and domU. In mem_event_enable(),the function
alloc_unbound_xen_event_channel()
> allocates a free port for domU, and then it will be bound with dom0.
> When xenpaging tears down,it just frees dom0''s event channel port
by
> xc_evtchn_unbind(), leaves domU''s port still occupied.
>     So we add the patch to free domU''s port when xenpaging exits.
> We need double free interdomain eventchannel. First free domainU port,
> and leave domain 0 port unbond, Then free domain 0 port.
> 
> Signed-off-by??Kaixing Hong <hongkaixing@huawei.com>,
> Signed-off-by??Zhen Shi <bicky.shi@huawei.com>
Acked-by: Olaf Hering <olaf@aepfle.de>