[Xen-changelog] [xen-4.0-testing] [shadow] Disable higher level pagetables early unshadow only when the "process dying" hypercall is used.

[Xen patchbot-4.0-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Gianluca Guida <gianluca.guida@xxxxxxxxxx>
# Date 1321461605 0
# Node ID c16b0a997a05e32b38fb33a70d59523375186f9c
# Parent  cdff7052bad8e0ee5fce18c9db54386b517c7d96
[shadow] Disable higher level pagetables early unshadow only when the "process 
dying" hypercall is used.

This patch fixes a performance problem in fully virtualized guests.

Signed-off-by: Gianluca Guida <gianluca.guida@xxxxxxxxxx>
Tested-by: Jan Beulich <jbeulich@xxxxxxxx>
Committed-by: Keir Fraser <keir@xxxxxxx>
xen-unstable changeset:   24148:3ecc8fef4281
xen-unstable date:        Wed Nov 16 15:19:33 2011 +0000
---


diff -r cdff7052bad8 -r c16b0a997a05 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Sat Nov 12 16:15:19 2011 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c    Wed Nov 16 16:40:05 2011 +0000
@@ -2710,8 +2710,9 @@
            || ( !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 */ );

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