[Xen-changelog] [xen stable-4.5] x86/paging: don't unconditionally BUG() on finding SHARED_M2P_ENTRY

[patchbot@xxxxxxx]

commit 62cc20d4cb872e9db0ba6da3fb32817c410e7a8a
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Dec 12 15:13:30 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Dec 12 15:13:30 2017 +0100

    x86/paging: don't unconditionally BUG() on finding SHARED_M2P_ENTRY
    
    PV guests can fully control the values written into the P2M.
    
    This is XSA-251.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: b4d0218cff66b7eaa9c9b8dc9bd71e7b089b016d
    master date: 2017-12-12 14:30:17 +0100
---
 xen/arch/x86/mm/paging.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/mm/paging.c b/xen/arch/x86/mm/paging.c
index 8d7f5cb..149a59a 100644
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -285,7 +285,7 @@ void paging_mark_dirty(struct domain *d, unsigned long 
guest_mfn)
     /* We /really/ mean PFN here, even for non-translated guests. */
     pfn = get_gpfn_from_mfn(mfn_x(gmfn));
     /* Shared MFNs should NEVER be marked dirty */
-    BUG_ON(SHARED_M2P(pfn));
+    BUG_ON(paging_mode_translate(d) && SHARED_M2P(pfn));
 
     /*
      * Values with the MSB set denote MFNs that aren't really part of the
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.5

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