[Xen-devel] [PATCH] x86/HVM: correct repeat count update in linear->phys translation

["Jan Beulich" <JBeulich@xxxxxxxx>]

For the insn emulator's fallback logic in REP MOVS/STOS/INS/OUTS
handling to work correctly, *reps must not be set to zero when
returning X86EMUL_UNHANDLEABLE.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -566,15 +566,16 @@ static int hvmemul_linear_to_phys(
             if ( pfec & (PFEC_page_paged | PFEC_page_shared) )
                 return X86EMUL_RETRY;
             done /= bytes_per_rep;
-            *reps = done;
             if ( done == 0 )
             {
                 ASSERT(!reverse);
                 if ( npfn != gfn_x(INVALID_GFN) )
                     return X86EMUL_UNHANDLEABLE;
+                *reps = 0;
                 x86_emul_pagefault(pfec, addr & PAGE_MASK, 
&hvmemul_ctxt->ctxt);
                 return X86EMUL_EXCEPTION;
             }
+            *reps = done;
             break;
         }
 




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