[XEN] Add 'insn_fetch' memory operation to the x86_emulator.

This can be used to perform correct access checks, provide appropriate
error codes when injecting faults, and to implement an
instruction-stream prefetch cache (which is included here for HVM PTE
update emulations).

Signed-off-by: Keir Fraser <keir@xensource.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/xen/include/asm-x86/x86_emulate.h b/xen/include/asm-x86/x86_emulate.h
index ef23291cdc..89a42da7b0 100644
--- a/xen/include/asm-x86/x86_emulate.h
+++ b/xen/include/asm-x86/x86_emulate.h
@@ -56,7 +56,8 @@ struct x86_emulate_ops
     /*
      * All functions:
      *  @seg:   [IN ] Segment being dereferenced (specified as x86_seg_??).
-     *  @offset [IN ] Offset within segment.
+     *  @offset:[IN ] Offset within segment.
+     *  @ctxt:  [IN ] Emulation context info as passed to the emulator.
      */
 
     /*
@@ -72,6 +73,17 @@ struct x86_emulate_ops
         struct x86_emulate_ctxt *ctxt);
 
     /*
+     * insn_fetch: Emulate fetch from instruction byte stream.
+     *  Parameters are same as for 'read'. @seg is always x86_seg_cs.
+     */
+    int (*insn_fetch)(
+        enum x86_segment seg,
+        unsigned long offset,
+        unsigned long *val,
+        unsigned int bytes,
+        struct x86_emulate_ctxt *ctxt);
+
+    /*
      * write: Emulate a memory write.
      *  @val:   [IN ] Value to write to memory (low-order bytes used as req'd).
      *  @bytes: [IN ] Number of bytes to write to memory.