[Xen-changelog] [xen-4.0-testing] x86 EPT: Only flush EPT TLB if the previous entry was valid

["Xen patchbot-4.0-testing" <patchbot-4.0-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1274858891 -3600
# Node ID 2758a8028721c84e5349405b4f0984b065738c22
# Parent  aa5ae409b1794108274e36c344f4e394e14184ee
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-unstable changeset:   21455:32cdd423d4eb
xen-unstable date:        Wed May 26 08:08:46 2010 +0100
---
 xen/arch/x86/mm/hap/p2m-ept.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletion(-)

diff -r aa5ae409b179 -r 2758a8028721 xen/arch/x86/mm/hap/p2m-ept.c
--- a/xen/arch/x86/mm/hap/p2m-ept.c     Wed May 26 08:26:38 2010 +0100
+++ b/xen/arch/x86/mm/hap/p2m-ept.c     Wed May 26 08:28:11 2010 +0100
@@ -187,6 +187,7 @@ 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;
 
     /* We only support 4k and 2m pages now */
     BUG_ON(order && order != EPT_TABLE_ORDER);
@@ -223,6 +224,11 @@ 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) )
         {
@@ -333,7 +339,8 @@ 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 ( iommu_enabled && need_iommu(d) && need_modify_vtd_table )

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