From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gianluca Guida <glguida@gmail.com>
Subject: [PATCH] [shadow] Disable higher level pagetables early
 unshadow only when the "process dying" hypercall is used.
Date: Wed, 16 Nov 2011 05:44:50 -0800
Message-ID: <CAKpvNa2tp7Ha=8kOsYyTjnWyo46YPQU678iS9aq=CfbzDOf17A@mail.gmail.com>
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To: xen-devel@lists.xensource.com, Keir Fraser <keir@xen.org>
Cc: Tim Deegan <tim@xen.org>, Jan Beulich <JBeulich@suse.com>, Gianluca Guida <gianluca.guida@citrix.com>
List-Id: xen-devel@lists.xenproject.org

This patch fixes a performance problem in fully virtualized guests.

Should be backported to xen-4.0 and xen-4.1. This patch applies (with
slightly different offsets) to all three versions.

Signed-off-by: Gianluca Guida <gianluca.guida@citrix.com>
Tested-by: Jan Beulich <jbeulich@suse.com>

diff -r 068d3d55ce6e xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Tue Nov 01 19:03:38 2011 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c    Wed Nov 16 14:30:57 2011 -0800
@@ -2723,8 +2723,9 @@
            || ( !v->domain->arch.paging.shadow.pagetable_dying_op
                 &&
v->arch.paging.shadow.last_emulated_mfn_for_unshadow == mfn_x(gmfn) )
)
          && sh_mfn_is_a_page_table(gmfn)
-         && !(mfn_to_page(gmfn)->shadow_flags
-              & (SHF_L2_32|SHF_L2_PAE|SHF_L2H_PAE|SHF_L4_64)) )
+         && (!v->domain->arch.paging.shadow.pagetable_dying_op ||
+             !(mfn_to_page(gmfn)->shadow_flags
+               & (SHF_L2_32|SHF_L2_PAE|SHF_L2H_PAE|SHF_L4_64))) )
     {
         perfc_incr(shadow_early_unshadow);
         sh_remove_shadows(v, gmfn, 1, 0 /* Fast, can fail to unshadow */ );