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[Xen-devel] [PATCH] Allow max_pages to be set to less than tot_pages

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Subject: [Xen-devel] [PATCH] Allow max_pages to be set to less than tot_pages
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Thu, 21 Oct 2010 16:19:14 +0100
Delivery-date: Thu, 21 Oct 2010 08:20:09 -0700
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The memory allocation code sometimes needs to enforce that a guest
that's been told to balloon down isn't going to expand further (because
it's still executing a previous balloon-up operation).  That means being
able to set the desired max_pages even before the balloon driver has
brought tot_pages down to the right level.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>

diff -r 95226c6fe89b xen/common/domctl.c
--- a/xen/common/domctl.c       Mon Jun 01 11:31:38 2009 +0100
+++ b/xen/common/domctl.c       Mon Jun 01 15:41:41 2009 +0100
@@ -675,11 +675,11 @@
         new_max = op->u.max_mem.max_memkb >> (PAGE_SHIFT-10);
-        if ( new_max >= d->tot_pages )
-        {
-            d->max_pages = new_max;
-            ret = 0;
-        }
+        /* N.B. We removed a check that new_max >= current tot_pages;
+         * this means the domain will "ratchet" down to new_max.
+         * In the meantime tot will be > max. */
+        d->max_pages = new_max;
+        ret = 0;

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