x86/xen: correct bug in p2m list initialization

Commit 054954eb051f35e74b75a566a96fe756015352c8 ("xen: switch to
linear virtual mapped sparse p2m list") introduced an error.

During initialization of the p2m list a p2m identity area mapped by
a complete identity pmd entry has to be split up into smaller chunks
sometimes, if a non-identity pfn is introduced in this area.

If this non-identity pfn is not at index 0 of a p2m page the new
p2m page needed is initialized with wrong identity entries, as the
identity pfns don't start with the value corresponding to index 0,
but with the initial non-identity pfn. This results in weird wrong
mappings.

Correct the wrong initialization by starting with the correct pfn.

Cc: stable@vger.kernel.org # 3.19
Reported-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 740ae3026a148ec54800710427a455dc890351d3..9f93af56a5fc7bd4cf263406faf96f8a5fa56466 100644 (file)
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -563,7 +563,7 @@ static bool alloc_p2m(unsigned long pfn)
                if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
                        p2m_init(p2m);
                else
-                       p2m_init_identity(p2m, pfn);
+                       p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
 
                spin_lock_irqsave(&p2m_update_lock, flags);