x86/EPT: fix super page splitting when resolving EPT_MISCONFIG VM exits

Reported-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -352,6 +352,7 @@ bool_t ept_handle_misconfig(uint64_t gpa
                 {
                     if ( ept_split_super_page(p2m, &e, level, level - 1) )
                     {
+                        atomic_write_ept_entry(&epte[i], e);
                         unmap_domain_page(epte);
                         mfn = e.mfn;
                         continue;