x86/xen: correct bug in p2m list initialization

jgross1 · David Vrabel · commit b8f05c8803fc · 2015-02-27T14:53:19.000Z
Commit 054954e ("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
@@ -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);
 
