[Xen-changelog] [xen-unstable] x86 EPT: Only flush EPT TLB if the previous entry was valid

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1274857726 -3600
# Node ID 32cdd423d4ebab2b2d03a4501be08438c5dc7050
# Parent  23291daa9da48c474b630de82bbe2a3fadc363d3
x86 EPT: Only flush EPT TLB if the previous entry was valid

Original patch from George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
---
 xen/arch/x86/mm/hap/p2m-ept.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletion(-)

diff -r 23291daa9da4 -r 32cdd423d4eb xen/arch/x86/mm/hap/p2m-ept.c
--- a/xen/arch/x86/mm/hap/p2m-ept.c     Wed May 26 08:02:33 2010 +0100
+++ b/xen/arch/x86/mm/hap/p2m-ept.c     Wed May 26 08:08:46 2010 +0100
@@ -242,6 +242,7 @@ ept_set_entry(struct domain *d, unsigned
     int direct_mmio = (p2mt == p2m_mmio_direct);
     uint8_t ipat = 0;
     int need_modify_vtd_table = 1;
+    int needs_sync = 1;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
 
     if (  order != 0 )
@@ -276,6 +277,11 @@ ept_set_entry(struct domain *d, unsigned
     if ( i == walk_level )
     {
         /* We reached the level we're looking for */
+
+        /* No need to flush if the old entry wasn't valid */
+        if ( !(ept_entry->epte & 7) )
+            needs_sync = 0;
+
         if ( mfn_valid(mfn_x(mfn)) || direct_mmio || p2m_is_paged(p2mt) ||
              (p2mt == p2m_ram_paging_in_start) )
         {
@@ -336,7 +342,8 @@ out:
 out:
     unmap_domain_page(table);
 
-    ept_sync_domain(d);
+    if ( needs_sync )
+        ept_sync_domain(d);
 
     /* Now the p2m table is not shared with vt-d page table */
     if ( rv && iommu_enabled && need_iommu(d) && need_modify_vtd_table )

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