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[Xen-changelog] [xen-4.0-testing] libxc: after saving, unmap correct amo

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Subject: [Xen-changelog] [xen-4.0-testing] libxc: after saving, unmap correct amount for live_m2p
From: Xen patchbot-4.0-testing <patchbot@xxxxxxx>
Date: Tue, 31 May 2011 21:25:09 +0100
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# HG changeset patch
# User Jim Fehlig <jfehlig@xxxxxxxxxx>
# Date 1306571192 -3600
# Node ID 3220df717f1098ed40dd3dd66edb6a13673750e7
# Parent  5054ed412032e6f922861a303eaa144714e009d1
libxc: after saving, unmap correct amount for live_m2p

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

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

Ian Campbell writes:
> 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 [another hunk].

This change should be backported to relevant earlier trees. -iwj

From: Jim Fehlig <jfehlig@xxxxxxxxxx>
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Olaf Hering <olaf@xxxxxxxxx>
Acked-by: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Committed-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
xen-unstable changeset:   23373:171007b4e2c4
xen-unstable date:        Tue May 24 14:50:00 2011 +0100

diff -r 5054ed412032 -r 3220df717f10 tools/libxc/xc_domain_save.c
--- a/tools/libxc/xc_domain_save.c      Tue May 24 08:21:48 2011 +0100
+++ b/tools/libxc/xc_domain_save.c      Sat May 28 09:26:32 2011 +0100
@@ -820,7 +820,7 @@
     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);
@@ -1833,7 +1833,7 @@
         munmap(live_shinfo, PAGE_SIZE);
     if ( ctx->live_p2m )
-        munmap(ctx->live_p2m, P2M_FLL_ENTRIES * PAGE_SIZE);
+        munmap(ctx->live_p2m, P2M_FL_ENTRIES * PAGE_SIZE);
     if ( ctx->live_m2p )
         munmap(ctx->live_m2p, M2P_SIZE(ctx->max_mfn));

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