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

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Gianluca Guida <gianluca.guida@xxxxxxxxxx>
# Date 1321456773 0
# Node ID 3ecc8fef428138e4304ef11b47498981e63626b3
# Parent  a5f1d3b1612bb48e1cb09dc66b0909e3613dc855
[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>
---


diff -r a5f1d3b1612b -r 3ecc8fef4281 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Wed Nov 16 15:17:37 2011 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c    Wed Nov 16 15:19:33 2011 +0000
@@ -2728,8 +2728,9 @@
            || ( !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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