[Xen-devel] [PATCH v8 1/2] x86emul: New return code for unimplemented instruction

[Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>]

Enforce the distinction between an instruction not implemented by the
emulator and the failure to emulate that instruction by defining a new
return code, X86EMUL_UNIMPLEMENTED.

This value should only be used by the core emulator if it fails to decode
the current instruction, and not by any of the x86_emulate_ops
callbacks.

Signed-off-by: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/emulate.c             | 4 ++++
 xen/arch/x86/hvm/io.c                  | 2 ++
 xen/arch/x86/hvm/vmx/realmode.c        | 2 +-
 xen/arch/x86/mm/shadow/multi.c         | 2 +-
 xen/arch/x86/x86_emulate/x86_emulate.c | 8 ++++----
 xen/arch/x86/x86_emulate/x86_emulate.h | 6 ++++++
 6 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 3a8db21..28133c0 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2044,6 +2044,8 @@ int hvm_emulate_one_mmio(unsigned long mfn, unsigned long 
gla)
     switch ( rc )
     {
     case X86EMUL_UNHANDLEABLE:
+        /* fall-through */
+    case X86EMUL_UNIMPLEMENTED:
         hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG", &ctxt);
         break;
     case X86EMUL_EXCEPTION:
@@ -2113,6 +2115,8 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, 
unsigned int trapnr,
          * consistent with X86EMUL_RETRY.
          */
         return;
+    case X86EMUL_UNIMPLEMENTED:
+        /* fall-through */
     case X86EMUL_UNHANDLEABLE:
         hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx);
         hvm_inject_hw_exception(trapnr, errcode);
diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index 214ab30..af4e1dc 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -96,6 +96,8 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, 
const char *descr)
     switch ( rc )
     {
     case X86EMUL_UNHANDLEABLE:
+        /* fall-through */
+    case X86EMUL_UNIMPLEMENTED:
         hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt);
         return false;
 
diff --git a/xen/arch/x86/hvm/vmx/realmode.c b/xen/arch/x86/hvm/vmx/realmode.c
index 11bde58..fdbbee2 100644
--- a/xen/arch/x86/hvm/vmx/realmode.c
+++ b/xen/arch/x86/hvm/vmx/realmode.c
@@ -106,7 +106,7 @@ void vmx_realmode_emulate_one(struct hvm_emulate_ctxt 
*hvmemul_ctxt)
     if ( hvm_vcpu_io_need_completion(vio) || vio->mmio_retry )
         vio->io_completion = HVMIO_realmode_completion;
 
-    if ( rc == X86EMUL_UNHANDLEABLE )
+    if ( rc == X86EMUL_UNHANDLEABLE || rc == X86EMUL_UNIMPLEMENTED )
     {
         gdprintk(XENLOG_ERR, "Failed to emulate insn.\n");
         goto fail;
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index c9c2252..85fb165 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3486,7 +3486,7 @@ static int sh_page_fault(struct vcpu *v,
      * would be a good unshadow hint. If we *do* decide to unshadow-on-fault
      * then it must be 'failable': we cannot require the unshadow to succeed.
      */
-    if ( r == X86EMUL_UNHANDLEABLE )
+    if ( r == X86EMUL_UNHANDLEABLE || r == X86EMUL_UNIMPLEMENTED )
     {
         perfc_incr(shadow_fault_emulate_failed);
 #if SHADOW_OPTIMIZATIONS & SHOPT_FAST_EMULATION
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index 2201852..480bad9 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2577,7 +2577,7 @@ x86_decode(
                         d = twobyte_table[0x3a].desc;
                         break;
                     default:
-                        rc = X86EMUL_UNHANDLEABLE;
+                        rc = X86EMUL_UNIMPLEMENTED;
                         goto done;
                     }
                 }
@@ -2591,7 +2591,7 @@ x86_decode(
                 }
                 else
                 {
-                    rc = X86EMUL_UNHANDLEABLE;
+                    rc = X86EMUL_UNIMPLEMENTED;
                     goto done;
                 }
 
@@ -2871,7 +2871,7 @@ x86_decode(
 
     default:
         ASSERT_UNREACHABLE();
-        return X86EMUL_UNHANDLEABLE;
+        return X86EMUL_UNIMPLEMENTED;
     }
 
     if ( ea.type == OP_MEM )
@@ -7717,7 +7717,7 @@ x86_emulate(
 
     default:
     cannot_emulate:
-        rc = X86EMUL_UNHANDLEABLE;
+        rc = X86EMUL_UNIMPLEMENTED;
         goto done;
     }
 
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index 4ddf111..82812ca 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -133,6 +133,12 @@ struct x86_emul_fpu_aux {
   * Undefined behavior when used anywhere else.
   */
 #define X86EMUL_DONE           4
+ /*
+  * Current instruction is not implemented by the emulator.
+  * This value should only be returned by the core emulator if decode fails
+  * and not by any of the x86_emulate_ops callbacks.
+  */
+#define X86EMUL_UNIMPLEMENTED  5
 
 /* FPU sub-types which may be requested via ->get_fpu(). */
 enum x86_emulate_fpu_type {
-- 
2.7.4


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