[Xen-changelog] [xen-unstable] xenpaging: when populating a page, check if populating is already in progress

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

# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1290781293 0
# Node ID 48b10f9a436e6e1cab07773df0f287a2253f6316
# Parent  1793318b35e65e055586d4d11622f9c9d4221d36
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@xxxxxxxxx>
---
 xen/arch/x86/mm/p2m.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -r 1793318b35e6 -r 48b10f9a436e xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c     Fri Nov 26 14:20:39 2010 +0000
+++ b/xen/arch/x86/mm/p2m.c     Fri Nov 26 14:21:33 2010 +0000
@@ -2767,7 +2767,7 @@ void p2m_mem_paging_populate(struct p2m_
     /* 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);

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