xenpaging: when populating a page, check if populating is already in progress

p2m_mem_paging_populate can be called serveral times from different
vcpus. If the page is already in state p2m_ram_paging_in and has a new
valid mfn, invalidating this new mfn will cause trouble later if
p2m_mem_paging_resume will set the new gfn/mfn pair back to state
p2m_ram_rw.  Detect this situation and keep p2m state if the page is
in the process of being still paged-out or already paged-in.  In fact,
p2m state p2m_ram_paged is the only state where the mfn type can be
invalidated.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 847a59ad66d4478b31e0ee8e8a3a5a7efe805d74..d7da4ad1f2509549520fe2b4ec1abf125bb683f4 100644 (file)
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -2767,7 +2767,7 @@ void p2m_mem_paging_populate(struct p2m_domain *p2m, unsigned long gfn)
     /* XXX: It seems inefficient to have this here, as it's only needed
      *      in one case (ept guest accessing paging out page) */
     gfn_to_mfn(p2m, gfn, &p2mt);
-    if ( p2mt != p2m_ram_paging_out )
+    if ( p2mt == p2m_ram_paged )
     {
         p2m_lock(p2m);
         set_p2m_entry(p2m, gfn, _mfn(PAGING_MFN), 0, p2m_ram_paging_in_start);