xen/xenpaging.p2m_mem_paging_populate_if_p2m_ram_paged.patch

Subject: 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 change p2m state not 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.

(xen-unstable changeset:   22443:48b10f9a436e)

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

---
 xen/arch/x86/mm/p2m.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- xen-4.0.1-testing.orig/xen/arch/x86/mm/p2m.c
+++ xen-4.0.1-testing/xen/arch/x86/mm/p2m.c
@@ -2577,7 +2577,7 @@ void p2m_mem_paging_populate(struct doma
     /* 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(d, gfn, &p2mt);
-    if ( p2mt != p2m_ram_paging_out )
+    if ( p2mt == p2m_ram_paged )
     {
         p2m_lock(d->arch.p2m);
         set_p2m_entry(d, gfn, _mfn(PAGING_MFN), 0, p2m_ram_paging_in_start);