[Xen-changelog] [xen stable-4.4] x86/p2m-ept: don't unmap the EPT pagetable while it is still in use

[patchbot@xxxxxxx]

commit cc87ed9e0576bee556120dc1fd0e3d7e339e860d
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Jul 21 11:16:24 2015 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jul 21 11:16:24 2015 +0200

    x86/p2m-ept: don't unmap the EPT pagetable while it is still in use
    
    The call to iommu_pte_flush() between the two hunks uses &ept_entry->epte
    which is a pointer into the mapped page.
    
    It is eventually passed to `clflush` instruction which will suffer a 
pagefault
    if the virtual mapping has fallen out of the TLB.
    
        (XEN) ----[ Xen-4.5.0-xs102594-d  x86_64  debug=y  Not tainted ]----
        (XEN) CPU:    7
        (XEN) RIP:    e008:[<ffff82d0801572f0>] cacheline_flush+0x4/0x9
        <snip>
        (XEN) Xen call trace:
        (XEN)    [<ffff82d0801572f0>] cacheline_flush+0x4/0x9
        (XEN)    [<ffff82d08014ffff>] __iommu_flush_cache+0x4a/0x6a
        (XEN)    [<ffff82d0801532e2>] iommu_pte_flush+0x2b/0xd5
        (XEN)    [<ffff82d0801f909a>] ept_set_entry+0x4bc/0x61f
        (XEN)    [<ffff82d0801f0c25>] p2m_set_entry+0xd1/0x112
        (XEN)    [<ffff82d0801f25b1>] clear_mmio_p2m_entry+0x1a0/0x200
        (XEN)    [<ffff82d0801f4aac>] unmap_mmio_regions+0x49/0x73
        (XEN)    [<ffff82d080106292>] do_domctl+0x15bd/0x1edb
        (XEN)    [<ffff82d080234fcb>] syscall_enter+0xeb/0x145
        (XEN)
        (XEN) Pagetable walk from ffff820040004ae0:
        (XEN)  L4[0x104] = 00000008668a5063 ffffffffffffffff
        (XEN)  L3[0x001] = 00000008668a3063 ffffffffffffffff
        (XEN)  L2[0x000] = 000000086689c063 ffffffffffffffff
        (XEN)  L1[0x004] = 000000056f078063 000000000007f678
        (XEN)
        (XEN) ****************************************
        (XEN) Panic on CPU 7:
        (XEN) FATAL PAGE FAULT
        (XEN) [error_code=0000]
        (XEN) Faulting linear address: ffff820040004ae0
        (XEN) ****************************************
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: e4e9d2d4e76bd8fe229c124bd57fc6ba824271b3
    master date: 2015-07-07 11:37:26 +0200
---
 xen/arch/x86/mm/p2m-ept.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 468033a..bdc95e0 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -440,8 +440,6 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, 
mfn_t mfn,
     rv = 1;
 
 out:
-    unmap_domain_page(table);
-
     if ( needs_sync )
         ept_sync_domain(p2m);
 
@@ -479,6 +477,8 @@ out:
         }
     }
 
+    unmap_domain_page(table);
+
     /* Release the old intermediate tables, if any.  This has to be the
        last thing we do, after the ept_sync_domain() and removal
        from the iommu tables, so as to avoid a potential
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.4

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