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Re: [Xen-devel] [PATCH] libxc: use correct macro when unmapping memory a

To: Jim Fehlig <jfehlig@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] libxc: use correct macro when unmapping memory after save operation
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Mon, 23 May 2011 10:16:51 +0100
Cc: Olaf Hering <olaf@xxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Fri, 2011-05-20 at 23:04 +0100, Jim Fehlig wrote:
> With some help from Olaf, I've finally got to the bottom of an issue I
> came across while trying to implement save/restore in the libvirt
> libxenlight driver.  After issuing the save operation, the saved domain
> was not being cleaned up properly and left in this state from xl's
> perspective
> xen33:# xl list
> Name                   ID   Mem VCPUs      State   Time(s)
> Domain-0                0  6821     8     r-----     122.5
> (null)                  2     2     2     --pssd      10.8
> Checking the libvirtd /proc/$pid/maps I found this
> 7f3798984000-7f3798b86000 r--s 00002000 00:03 4026532097 /proc/xen/privcmd
> So not all all pages belonging to the domain were unmapped from
> libvirtd.  In tools/libxc/xc_domain_save.c we found that P2M_FL_ENTRIES
> were being mapped but only P2M_FLL_ENTRIES were being unmapped.  The
> attached patch changes the unmapping to use the same P2M_FL_ENTRIES
> macro.  I'm not too familiar with this code though so posting here for
> review.
> I suspect this was not noticed before since most (all?) processes doing
> save terminate after the save and are not long-running like libvirtd.

Good catch!

Looks like I introduced this in 18558:ccf0205255e1, sorry!

I guess it is also wrong in the error path out of map_and_save_p2m_table
and so we also need:

diff -r 35ae855173fa tools/libxc/xc_domain_save.c
--- a/tools/libxc/xc_domain_save.c      Mon May 23 10:06:23 2011 +0100
+++ b/tools/libxc/xc_domain_save.c      Mon May 23 10:15:43 2011 +0100
@@ -861,7 +861,7 @@ static xen_pfn_t *map_and_save_p2m_table
     if ( !success && p2m )
-        munmap(p2m, P2M_FLL_ENTRIES * PAGE_SIZE);
+        munmap(p2m, P2M_FL_ENTRIES * PAGE_SIZE);
     if ( live_p2m_frame_list_list )
         munmap(live_p2m_frame_list_list, PAGE_SIZE);

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