[Xen-changelog] [xen staging] x86/HVM: hvmemul_cmpxchg() should also use known_gla()

[patchbot@xxxxxxx]

commit 2262e808f4665bee820b5bb536aff47e560bdcc3
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Nov 15 13:36:52 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Nov 15 13:36:52 2018 +0100

    x86/HVM: hvmemul_cmpxchg() should also use known_gla()
    
    To be consistent with the write and rmw cases the mapping approach
    should not be used when the guest linear address translation is known.
    This in particular excludes the discard-write case from bypassing the
    emulation path. This also means that now EFLAGS should actually get
    properly updated, despite the discarded write portion of the memory
    access.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
 xen/arch/x86/hvm/emulate.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index e08524be49..488ea5e956 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1472,9 +1472,12 @@ static int hvmemul_cmpxchg(
     else if ( hvmemul_ctxt->seg_reg[x86_seg_ss].dpl == 3 )
         pfec |= PFEC_user_mode;
 
-    mapping = hvmemul_map_linear_addr(addr, bytes, pfec, hvmemul_ctxt);
-    if ( IS_ERR(mapping) )
-        return ~PTR_ERR(mapping);
+    if ( !known_gla(addr, bytes, pfec) )
+    {
+        mapping = hvmemul_map_linear_addr(addr, bytes, pfec, hvmemul_ctxt);
+        if ( IS_ERR(mapping) )
+            return ~PTR_ERR(mapping);
+    }
 
     if ( !mapping )
     {
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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