[Xen-devel] [PATCH] xen: Disable RAM-to-RAM copy in hvmemul_rep_movs() when mem_access_emulate_enabled

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

The mem_access client might want to use hvm_emulate_one_no_write(),
in which case the RAM-to-RAM copy code in hvmemul_rep_movs() would
lead to an unwanted (and unexpected) write operation.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/emulate.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 40de776..4cc7e01 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -951,6 +951,14 @@ static int hvmemul_rep_movs(
         return hvmemul_do_mmio(
             dgpa, reps, bytes_per_rep, sgpa, IOREQ_WRITE, df, NULL);
 
+    /*
+     * The mem_access client might want to call hvm_emulate_one_no_write(),
+     * in which case going ahead would lead to an unwanted write.
+     * Fall back to slow emulation instead.
+     */
+    if ( unlikely(current->domain->arch.mem_access_emulate_enabled) )
+        return X86EMUL_UNHANDLEABLE;
+
     /* RAM-to-RAM copy: emulate as equivalent of memmove(dgpa, sgpa, bytes). */
     bytes = *reps * bytes_per_rep;
 
-- 
1.7.9.5


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