[PATCH v12 0/4] Notify monitor when emulating an unimplemented instruction

[PATCH v12 0/4] Notify monitor when emulating an unimplemented instruction

[Petre Pircalabu]

This patchset implements a mechanism which allows XEN to send first an event
if the emulator encountered an unsupported instruction.
The monitor application can choose to mitigate the error, for example to singlestep
the instruction using the real processor and then resume execution of the normal
instruction flow.

This feature was tested using a modified version of XTF:
https://github.com/petrepircalabu/xen-test-framework/tree/emul_unimpl

---
Changed since v1:
  * Removed the emulation kind check when calling hvm_inject_hw_exception

Changed since v2:
  * Removed a file added by mistake

Changed since v3:
  * Removed extra stray line
  * Added the _enabled suffix to the emul_unhandleable monitor option

Changed since v4
  * Fixed return expression of hvm_monitor_emul_unhandleable handle
  monitor_traps failures.
  * Removed stray parantheses.

Changed since v5:
  * Removed unnecessary "else" when calling hvm_monitor_emul_unhandleable.
  * Added extra line in arch_monitor_domctl_event.

Changed since v6:
  * add the distinction between unimplemented instructions and emulation failures.
  * changed "emul_unhandleable" event name to "emul_unimplemented"

Changed since v7:
  * Add "fall-through" comments to the switch statements (coverity)
  * Added X86EMUL_UNIMPLEMENTED to X86EMUL_UNHANDLEABLE checks the in functions
  referencing x86_emulate.
  * Improved comment describing X86EMUL_UNIMPLEMENTED.

Changed since v8:
  * Removed unnecessary "fall-through" comments.
  * Added check for X86EMUL_UNIMPLEMENTED in hvm_ud_intercept.
  * add a new label 'unimplemented_insn' to accomodate the existing jumps to
  'cannot_emulate' (e.g. invoke_stub)

Changed since v9:
  * Added detailed description in the patch comment regarding the usage (and lack of it) 
  of the new X86EMUL_UNIMPLEMENTED return code.
  * removed 'cannot_emulate' label.
  * added local vimrc files to the gitignore list.

Changed since v10:
  * Added asserts to make sure the return code cannot be X86EMUL_UNIMPLEMENTED.
  * Added new return code (X86EMUL_UNRECOGNIZED) to be used when trying
  to emulate an instruction with an invalid opcode.
  * Added emulation return code information to error messages.
  * Raise #UD when emulating an unimplemented instruction instead of just crash the domain

Changed since v11:
    * Fixed double negative comment.
    * Move assertion into the switch and use ASSERT_UNREACHABLE() when
    applicable.
    * Changed the description of X86EMUL_UNIMPLEMENTED / X86EMUL_UNRECOGNIZED
    to reflect the differences between those 2 return codes.
    * Changed the returned value to X86EMUL_UNRECOGNIZED in some cases (a detailed list is
    provided in the patch description)
    * Removed "rc=" from the error message.
    * Check for X86EMUL_UNRECOGNIZED instead of X86EMUL_UNIMPLEMENTED when generating an
    Invalid Opcode trap


Petre Pircalabu (4):
  x86emul: New return code for unimplemented instruction
  x86emul: Add return code information to error messages
  x86/monitor: Notify monitor if an emulation fails.
  x86emul: Raise #UD when emulating an unrecognized instruction.

 tools/libxc/include/xenctrl.h          |  2 ++
 tools/libxc/xc_monitor.c               | 14 +++++++++
 xen/arch/x86/hvm/emulate.c             | 30 ++++++++++++++++----
 xen/arch/x86/hvm/hvm.c                 |  1 +
 xen/arch/x86/hvm/io.c                  |  7 ++++-
 xen/arch/x86/hvm/monitor.c             | 17 +++++++++++
 xen/arch/x86/hvm/vmx/realmode.c        | 11 ++++++-
 xen/arch/x86/mm/shadow/multi.c         |  6 ++--
 xen/arch/x86/monitor.c                 | 13 +++++++++
 xen/arch/x86/x86_emulate/x86_emulate.c | 52 ++++++++++++++++++++--------------
 xen/arch/x86/x86_emulate/x86_emulate.h | 13 +++++++++
 xen/include/asm-x86/domain.h           |  1 +
 xen/include/asm-x86/hvm/emulate.h      |  2 +-
 xen/include/asm-x86/hvm/monitor.h      |  1 +
 xen/include/asm-x86/monitor.h          |  3 +-
 xen/include/public/domctl.h            |  1 +
 xen/include/public/vm_event.h          |  2 ++
 17 files changed, 142 insertions(+), 34 deletions(-)

-- 
2.7.4


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[PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Petre Pircalabu]

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 returned by the core emulator only if it fails to
properly decode the current instruction's opcode, and not by any of other
functions, such as the x86_emulate_ops or the hvm_io_ops callbacks.

e.g. hvm_process_io_intercept should not return X86EMUL_UNIMPLEMENTED.
The return value of this function depends on either the return code of
one of the hvm_io_ops handlers (read/write) or the value returned by
hvm_copy_guest_from_phys / hvm_copy_to_guest_phys.

Similary, none of this functions should return X86EMUL_UNIMPLEMENTED.
 - hvm_io_intercept
 - hvmemul_do_io
 - hvm_send_buffered_ioreq
 - hvm_send_ioreq
 - hvm_broadcast_ioreq
 - hvmemul_do_io_buffer
 - hvmemul_validate

Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>

---
Changed since v10:
    * Added asserts to make sure the return code cannot be X86EMUL_UNIMPLEMENTED.
    * Add new return code (X86EMUL_UNRECOGNIZED) to be used when trying
    to emulate an instruction with an invalid opcode.

Changed since v11:
    * Fixed double negative in the patch description.
    * Move assertion into the switch and use ASSERT_UNREACHABLE() when
    applicable.
    * Changed the description of X86EMUL_UNIMPLEMENTED / X86EMUL_UNRECOGNIZED
    to reflect the differences between those 2 return codes.
    * Changed the returned value to X86EMUL_UNRECOGNIZED in the
    following cases:
        X86EMUL_OPC(0x0f, 0x73): /* Group 14 */
        X86EMUL_OPC_66(0x0f, 0x73):
        X86EMUL_OPC_VEX_66(0x0f, 0x73):
                - All valid opcodes are defined, so it should return
                X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.

        X86EMUL_OPC(0x0f, 0xc7) /* Group 9 */
                - For register type instructions all possible opcodes are
                defined, so it should return X86EMUL_UNRECOGNIZED if
                mod R/M bits are not matched.

        X86EMUL_OPC_VEX(0x0f38, 0xf3): /* Group 17 */
                - All valid opcodes are defined, so it should return
                X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.

        X86EMUL_OPC_XOP(09, 0x01): /* XOP Grp1 */
        X86EMUL_OPC_XOP(09, 0x02): /* XOP Grp2 */
                - All valid opcodes are defined, so it should return
                X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.

        X86EMUL_OPC(0x0f, 0x01): /* Grp7 */
                - Not all valid opcodes are defined so it should return
                X86EMUL_UNIMPLEMENTED if mod R/M bits are not matched.
                (e.g. XGETBV)

        X86EMUL_OPC_66(0x0f, 0x78):
                - All valid opcodes are defined, so it should return
                X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.

        X86EMUL_OPC(0x0f, 0xae):
        X86EMUL_OPC_66(0x0f, 0xae): /* Grp15 */
                - Not all valid opcodes are defined so it should return
                X86EMUL_UNIMPLEMENTED if mod R/M bits are not matched.
                (e.g. FXSAVE/FXRSTOR )
---
 xen/arch/x86/hvm/emulate.c             | 12 ++++++++
 xen/arch/x86/hvm/hvm.c                 |  1 +
 xen/arch/x86/hvm/io.c                  |  1 +
 xen/arch/x86/hvm/vmx/realmode.c        |  2 +-
 xen/arch/x86/mm/shadow/multi.c         |  2 +-
 xen/arch/x86/x86_emulate/x86_emulate.c | 52 ++++++++++++++++++++--------------
 xen/arch/x86/x86_emulate/x86_emulate.h | 13 +++++++++
 7 files changed, 60 insertions(+), 23 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index cc874ce..385fe1e 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -284,10 +284,15 @@ static int hvmemul_do_io(
         }
         break;
     }
+    case X86EMUL_UNIMPLEMENTED:
+        ASSERT_UNREACHABLE();
+        /* Fall-through */
     default:
         BUG();
     }
 
+    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
+
     if ( rc != X86EMUL_OKAY )
         return rc;
 
@@ -313,6 +318,9 @@ static int hvmemul_do_io_buffer(
 
     rc = hvmemul_do_io(is_mmio, addr, reps, size, dir, df, 0,
                        (uintptr_t)buffer);
+
+    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
+
     if ( rc == X86EMUL_UNHANDLEABLE && dir == IOREQ_READ )
         memset(buffer, 0xff, size);
 
@@ -405,6 +413,8 @@ static int hvmemul_do_io_addr(
     rc = hvmemul_do_io(is_mmio, addr, &count, size, dir, df, 1,
                        ram_gpa);
 
+    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
+
     if ( rc == X86EMUL_OKAY )
         v->arch.hvm_vcpu.hvm_io.mmio_retry = (count < *reps);
 
@@ -2045,6 +2055,7 @@ int hvm_emulate_one_mmio(unsigned long mfn, unsigned long gla)
     switch ( rc )
     {
     case X86EMUL_UNHANDLEABLE:
+    case X86EMUL_UNIMPLEMENTED:
         hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG", &ctxt);
         break;
     case X86EMUL_EXCEPTION:
@@ -2102,6 +2113,7 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
          * consistent with X86EMUL_RETRY.
          */
         return;
+    case X86EMUL_UNIMPLEMENTED:
     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/hvm.c b/xen/arch/x86/hvm/hvm.c
index 93394c1..43ff5aa 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3723,6 +3723,7 @@ void hvm_ud_intercept(struct cpu_user_regs *regs)
     switch ( hvm_emulate_one(&ctxt) )
     {
     case X86EMUL_UNHANDLEABLE:
+    case X86EMUL_UNIMPLEMENTED:
         hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
         break;
     case X86EMUL_EXCEPTION:
diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index bf41954..984db21 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -96,6 +96,7 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, const char *descr)
     switch ( rc )
     {
     case X86EMUL_UNHANDLEABLE:
+    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 12d43ad..cf48139 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 8d4f244..2557e21 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3488,7 +3488,7 @@ 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 c1e2300..f334de9 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -848,7 +848,8 @@ do{ asm volatile (                                                      \
                 stub.func);                                             \
         generate_exception_if(res_.fields.trapnr == EXC_UD, EXC_UD);    \
         domain_crash(current->domain);                                  \
-        goto cannot_emulate;                                            \
+        rc = X86EMUL_UNHANDLEABLE;                                      \
+        goto done;                                                      \
     }                                                                   \
 } while (0)
 #else
@@ -2585,7 +2586,7 @@ x86_decode(
                         d = twobyte_table[0x3a].desc;
                         break;
                     default:
-                        rc = X86EMUL_UNHANDLEABLE;
+                        rc = X86EMUL_UNRECOGNIZED;
                         goto done;
                     }
                 }
@@ -2599,7 +2600,7 @@ x86_decode(
                 }
                 else
                 {
-                    rc = X86EMUL_UNHANDLEABLE;
+                    rc = X86EMUL_UNRECOGNIZED;
                     goto done;
                 }
 
@@ -2879,7 +2880,7 @@ x86_decode(
 
     default:
         ASSERT_UNREACHABLE();
-        return X86EMUL_UNHANDLEABLE;
+        return X86EMUL_UNIMPLEMENTED;
     }
 
     if ( ea.type == OP_MEM )
@@ -4191,7 +4192,7 @@ x86_emulate(
                 break;
             case 4: /* fldenv - TODO */
                 state->fpu_ctrl = true;
-                goto cannot_emulate;
+                goto unimplemented_insn;
             case 5: /* fldcw m2byte */
                 state->fpu_ctrl = true;
                 if ( (rc = ops->read(ea.mem.seg, ea.mem.off, &src.val,
@@ -4202,7 +4203,7 @@ x86_emulate(
                 break;
             case 6: /* fnstenv - TODO */
                 state->fpu_ctrl = true;
-                goto cannot_emulate;
+                goto unimplemented_insn;
             case 7: /* fnstcw m2byte */
                 state->fpu_ctrl = true;
                 emulate_fpu_insn_memdst("fnstcw", dst.val);
@@ -4438,7 +4439,7 @@ x86_emulate(
             case 4: /* frstor - TODO */
             case 6: /* fnsave - TODO */
                 state->fpu_ctrl = true;
-                goto cannot_emulate;
+                goto unimplemented_insn;
             case 7: /* fnstsw m2byte */
                 state->fpu_ctrl = true;
                 emulate_fpu_insn_memdst("fnstsw", dst.val);
@@ -5197,7 +5198,7 @@ x86_emulate(
 #undef _GRP7
 
         default:
-            goto cannot_emulate;
+            goto unimplemented_insn;
         }
         break;
     }
@@ -6195,7 +6196,7 @@ x86_emulate(
                 /* vpsll{w,d} $imm8,{x,y}mm,{x,y}mm */
             break;
         default:
-            goto cannot_emulate;
+            goto unimplemented_insn;
         }
     simd_0f_shift_imm:
         generate_exception_if(ea.type != OP_REG, EXC_UD);
@@ -6243,7 +6244,8 @@ x86_emulate(
         case 6: /* psllq $imm8,mm */
             goto simd_0f_shift_imm;
         }
-        goto cannot_emulate;
+        rc = X86EMUL_UNRECOGNIZED;
+        goto done;
 
     case X86EMUL_OPC_66(0x0f, 0x73):
     case X86EMUL_OPC_VEX_66(0x0f, 0x73):
@@ -6259,7 +6261,8 @@ x86_emulate(
                 /* vpslldq $imm8,{x,y}mm,{x,y}mm */
             goto simd_0f_shift_imm;
         }
-        goto cannot_emulate;
+        rc = X86EMUL_UNRECOGNIZED;
+        goto done;
 
     case X86EMUL_OPC(0x0f, 0x77):        /* emms */
     case X86EMUL_OPC_VEX(0x0f, 0x77):    /* vzero{all,upper} */
@@ -6323,7 +6326,8 @@ x86_emulate(
         case 0: /* extrq $imm8,$imm8,xmm */
             break;
         default:
-            goto cannot_emulate;
+            rc = X86EMUL_UNRECOGNIZED;
+            goto done;
         }
         /* fall through */
     case X86EMUL_OPC_F2(0x0f, 0x78):     /* insertq $imm8,$imm8,xmm,xmm */
@@ -6518,7 +6522,7 @@ x86_emulate(
                 goto done;
             break;
         default:
-            goto cannot_emulate;
+            goto unimplemented_insn;
         }
         break;
 
@@ -6534,7 +6538,8 @@ x86_emulate(
             vcpu_must_have(avx);
             goto stmxcsr;
         }
-        goto cannot_emulate;
+        rc = X86EMUL_UNRECOGNIZED;
+        goto done;
 
     case X86EMUL_OPC_F3(0x0f, 0xae): /* Grp15 */
         fail_if(modrm_mod != 3);
@@ -6777,7 +6782,8 @@ x86_emulate(
             switch ( modrm_reg & 7 )
             {
             default:
-                goto cannot_emulate;
+                rc = X86EMUL_UNRECOGNIZED;
+                goto done;
 
 #ifdef HAVE_GAS_RDRAND
             case 6: /* rdrand */
@@ -7359,7 +7365,8 @@ x86_emulate(
             host_and_vcpu_must_have(bmi1);
             break;
         default:
-            goto cannot_emulate;
+            rc = X86EMUL_UNRECOGNIZED;
+            goto done;
         }
 
         generate_exception_if(vex.l, EXC_UD);
@@ -7670,7 +7677,8 @@ x86_emulate(
             host_and_vcpu_must_have(tbm);
             break;
         default:
-            goto cannot_emulate;
+            rc = X86EMUL_UNRECOGNIZED;
+            goto done;
         }
 
     xop_09_rm_rv:
@@ -7704,7 +7712,8 @@ x86_emulate(
             host_and_vcpu_must_have(tbm);
             goto xop_09_rm_rv;
         }
-        goto cannot_emulate;
+        rc = X86EMUL_UNRECOGNIZED;
+        goto done;
 
     case X86EMUL_OPC_XOP(0a, 0x10): /* bextr imm,r/m,r */
     {
@@ -7736,8 +7745,8 @@ x86_emulate(
     }
 
     default:
-    cannot_emulate:
-        rc = X86EMUL_UNHANDLEABLE;
+    unimplemented_insn:
+        rc = X86EMUL_UNIMPLEMENTED;
         goto done;
     }
 
@@ -7789,7 +7798,8 @@ x86_emulate(
                 if ( (d & DstMask) != DstMem )
                 {
                     ASSERT_UNREACHABLE();
-                    goto cannot_emulate;
+                    rc = X86EMUL_UNHANDLEABLE;
+                    goto done;
                 }
                 break;
             }
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h b/xen/arch/x86/x86_emulate/x86_emulate.h
index 4ddf111..1fb74c0 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -133,6 +133,19 @@ 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 when a valid
+  * opcode is found but the execution logic for that instruction is missing.
+  * It should NOT be returned by any of the x86_emulate_ops callbacks.
+  */
+#define X86EMUL_UNIMPLEMENTED  5
+ /*
+  * The current instruction's opcode is not valid.
+  * If this error code is returned by a function, an #UD trap should be
+  * raised by the final consumer of it.
+ */
+#define X86EMUL_UNRECOGNIZED   X86EMUL_UNIMPLEMENTED
 
 /* FPU sub-types which may be requested via ->get_fpu(). */
 enum x86_emulate_fpu_type {
-- 
2.7.4


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[PATCH v12 2/4] x86emul: Add return code information to error messages

[Petre Pircalabu]

- print the return code of the last failed emulator operation
in hvm_dump_emulation_state.
- print the return code in sh_page_fault (SHADOW_PRINTK) to make the
distiction between X86EMUL_UNHANDLEABLE and X86EMUL_UNIMPLEMENTED.

Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

---
Changed since v11:
    * Removed "rc=" from the error message.
---
 xen/arch/x86/hvm/emulate.c        | 13 +++++++------
 xen/arch/x86/hvm/io.c             |  2 +-
 xen/arch/x86/hvm/vmx/realmode.c   |  2 +-
 xen/arch/x86/mm/shadow/multi.c    |  4 ++--
 xen/include/asm-x86/hvm/emulate.h |  2 +-
 5 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 385fe1e..4fe61b4 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2056,7 +2056,7 @@ int hvm_emulate_one_mmio(unsigned long mfn, unsigned long gla)
     {
     case X86EMUL_UNHANDLEABLE:
     case X86EMUL_UNIMPLEMENTED:
-        hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG", &ctxt);
+        hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG", &ctxt, rc);
         break;
     case X86EMUL_EXCEPTION:
         hvm_inject_event(&ctxt.ctxt.event);
@@ -2115,7 +2115,7 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
         return;
     case X86EMUL_UNIMPLEMENTED:
     case X86EMUL_UNHANDLEABLE:
-        hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx);
+        hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx, rc);
         hvm_inject_hw_exception(trapnr, errcode);
         break;
     case X86EMUL_EXCEPTION:
@@ -2243,16 +2243,17 @@ static const char *guest_x86_mode_to_str(int mode)
 }
 
 void hvm_dump_emulation_state(const char *loglvl, const char *prefix,
-                              struct hvm_emulate_ctxt *hvmemul_ctxt)
+                              struct hvm_emulate_ctxt *hvmemul_ctxt, int rc)
 {
     struct vcpu *curr = current;
     const char *mode_str = guest_x86_mode_to_str(hvm_guest_x86_mode(curr));
     const struct segment_register *cs =
         hvmemul_get_seg_reg(x86_seg_cs, hvmemul_ctxt);
 
-    printk("%s%s emulation failed: %pv %s @ %04x:%08lx -> %*ph\n",
-           loglvl, prefix, curr, mode_str, cs->sel, hvmemul_ctxt->insn_buf_eip,
-           hvmemul_ctxt->insn_buf_bytes, hvmemul_ctxt->insn_buf);
+    printk("%s%s emulation failed (%d): %pv %s @ %04x:%08lx -> %*ph\n",
+           loglvl, prefix, rc, curr, mode_str, cs->sel,
+           hvmemul_ctxt->insn_buf_eip, hvmemul_ctxt->insn_buf_bytes,
+           hvmemul_ctxt->insn_buf);
 }
 
 /*
diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index 984db21..7152c28 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -97,7 +97,7 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, const char *descr)
     {
     case X86EMUL_UNHANDLEABLE:
     case X86EMUL_UNIMPLEMENTED:
-        hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt);
+        hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt, rc);
         return false;
 
     case X86EMUL_EXCEPTION:
diff --git a/xen/arch/x86/hvm/vmx/realmode.c b/xen/arch/x86/hvm/vmx/realmode.c
index cf48139..b93792d 100644
--- a/xen/arch/x86/hvm/vmx/realmode.c
+++ b/xen/arch/x86/hvm/vmx/realmode.c
@@ -138,7 +138,7 @@ void vmx_realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt)
     return;
 
  fail:
-    hvm_dump_emulation_state(XENLOG_G_ERR, "Real-mode", hvmemul_ctxt);
+    hvm_dump_emulation_state(XENLOG_G_ERR, "Real-mode", hvmemul_ctxt, rc);
     domain_crash(curr->domain);
 }
 
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 2557e21..28030ac 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3498,8 +3498,8 @@ static int sh_page_fault(struct vcpu *v,
             v->arch.paging.last_write_emul_ok = 0;
         }
 #endif
-        SHADOW_PRINTK("emulator failure, unshadowing mfn %#lx\n",
-                       mfn_x(gmfn));
+        SHADOW_PRINTK("emulator failure (rc=%d), unshadowing mfn %#lx\n",
+                       r, mfn_x(gmfn));
         /* If this is actually a page table, then we have a bug, and need
          * to support more operations in the emulator.  More likely,
          * though, this is a hint that this page should not be shadowed. */
diff --git a/xen/include/asm-x86/hvm/emulate.h b/xen/include/asm-x86/hvm/emulate.h
index 8864775..58d17c4 100644
--- a/xen/include/asm-x86/hvm/emulate.h
+++ b/xen/include/asm-x86/hvm/emulate.h
@@ -92,7 +92,7 @@ int hvmemul_do_pio_buffer(uint16_t port,
                           void *buffer);
 
 void hvm_dump_emulation_state(const char *loglvl, const char *prefix,
-                              struct hvm_emulate_ctxt *hvmemul_ctxt);
+                              struct hvm_emulate_ctxt *hvmemul_ctxt, int rc);
 
 #endif /* __ASM_X86_HVM_EMULATE_H__ */
 
-- 
2.7.4


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[PATCH v12 3/4] x86/monitor: Notify monitor if an emulation fails.

[Petre Pircalabu]

If case of a vm_event with the emulate_flags set, if the instruction
is not implemented by the emulator, the monitor should be notified instead
of directly injecting a hw exception.
This behavior can be used to re-execute an instruction not supported by
the emulator using the real processor (e.g. altp2m) instead of just
crashing.

Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
 tools/libxc/include/xenctrl.h     |  2 ++
 tools/libxc/xc_monitor.c          | 14 ++++++++++++++
 xen/arch/x86/hvm/emulate.c        |  5 +++++
 xen/arch/x86/hvm/monitor.c        | 17 +++++++++++++++++
 xen/arch/x86/monitor.c            | 13 +++++++++++++
 xen/include/asm-x86/domain.h      |  1 +
 xen/include/asm-x86/hvm/monitor.h |  1 +
 xen/include/asm-x86/monitor.h     |  3 ++-
 xen/include/public/domctl.h       |  1 +
 xen/include/public/vm_event.h     |  2 ++
 10 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 073fbc9..5ea8b4c 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2028,6 +2028,8 @@ int xc_monitor_debug_exceptions(xc_interface *xch, domid_t domain_id,
 int xc_monitor_cpuid(xc_interface *xch, domid_t domain_id, bool enable);
 int xc_monitor_privileged_call(xc_interface *xch, domid_t domain_id,
                                bool enable);
+int xc_monitor_emul_unimplemented(xc_interface *xch, domid_t domain_id,
+                                  bool enable);
 /**
  * This function enables / disables emulation for each REP for a
  * REP-compatible instruction.
diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
index a677820..6046680 100644
--- a/tools/libxc/xc_monitor.c
+++ b/tools/libxc/xc_monitor.c
@@ -217,6 +217,20 @@ int xc_monitor_privileged_call(xc_interface *xch, domid_t domain_id,
     return do_domctl(xch, &domctl);
 }
 
+int xc_monitor_emul_unimplemented(xc_interface *xch, domid_t domain_id,
+                                  bool enable)
+{
+    DECLARE_DOMCTL;
+
+    domctl.cmd = XEN_DOMCTL_monitor_op;
+    domctl.domain = domain_id;
+    domctl.u.monitor_op.op = enable ? XEN_DOMCTL_MONITOR_OP_ENABLE
+                                    : XEN_DOMCTL_MONITOR_OP_DISABLE;
+    domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED;
+
+    return do_domctl(xch, &domctl);
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 4fe61b4..19e7035 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -14,12 +14,14 @@
 #include <xen/sched.h>
 #include <xen/paging.h>
 #include <xen/trace.h>
+#include <xen/vm_event.h>
 #include <asm/event.h>
 #include <asm/i387.h>
 #include <asm/xstate.h>
 #include <asm/hvm/emulate.h>
 #include <asm/hvm/hvm.h>
 #include <asm/hvm/ioreq.h>
+#include <asm/hvm/monitor.h>
 #include <asm/hvm/trace.h>
 #include <asm/hvm/support.h>
 #include <asm/hvm/svm/svm.h>
@@ -2114,6 +2116,9 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
          */
         return;
     case X86EMUL_UNIMPLEMENTED:
+        if ( hvm_monitor_emul_unimplemented() )
+            return;
+        /* fall-through */
     case X86EMUL_UNHANDLEABLE:
         hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx, rc);
         hvm_inject_hw_exception(trapnr, errcode);
diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
index 2787dfa..4ce778c 100644
--- a/xen/arch/x86/hvm/monitor.c
+++ b/xen/arch/x86/hvm/monitor.c
@@ -57,6 +57,23 @@ bool hvm_monitor_cr(unsigned int index, unsigned long value, unsigned long old)
     return 0;
 }
 
+bool hvm_monitor_emul_unimplemented(void)
+{
+    struct vcpu *curr = current;
+
+    /*
+     * Send a vm_event to the monitor to signal that the current
+     * instruction couldn't be emulated.
+     */
+    vm_event_request_t req = {
+        .reason = VM_EVENT_REASON_EMUL_UNIMPLEMENTED,
+        .vcpu_id  = curr->vcpu_id,
+    };
+
+    return curr->domain->arch.monitor.emul_unimplemented_enabled &&
+        monitor_traps(curr, true, &req) == 1;
+}
+
 void hvm_monitor_msr(unsigned int msr, uint64_t value)
 {
     struct vcpu *curr = current;
diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index 706454f..e59f1f5 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -283,6 +283,19 @@ int arch_monitor_domctl_event(struct domain *d,
         break;
     }
 
+    case XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED:
+    {
+        bool old_status = ad->monitor.emul_unimplemented_enabled;
+
+        if ( unlikely(old_status == requested_status) )
+            return -EEXIST;
+
+        domain_pause(d);
+        ad->monitor.emul_unimplemented_enabled = requested_status;
+        domain_unpause(d);
+        break;
+    }
+
     default:
         /*
          * Should not be reached unless arch_monitor_get_capabilities() is
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index fb8bf17..fcab8f8 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -406,6 +406,7 @@ struct arch_domain
         unsigned int cpuid_enabled                                         : 1;
         unsigned int descriptor_access_enabled                             : 1;
         unsigned int guest_request_userspace_enabled                       : 1;
+        unsigned int emul_unimplemented_enabled                            : 1;
         struct monitor_msr_bitmap *msr_bitmap;
         uint64_t write_ctrlreg_mask[4];
     } monitor;
diff --git a/xen/include/asm-x86/hvm/monitor.h b/xen/include/asm-x86/hvm/monitor.h
index cfd6661..6e22091 100644
--- a/xen/include/asm-x86/hvm/monitor.h
+++ b/xen/include/asm-x86/hvm/monitor.h
@@ -47,6 +47,7 @@ int hvm_monitor_cpuid(unsigned long insn_length, unsigned int leaf,
                       unsigned int subleaf);
 void hvm_monitor_interrupt(unsigned int vector, unsigned int type,
                            unsigned int err, uint64_t cr2);
+bool hvm_monitor_emul_unimplemented(void);
 
 #endif /* __ASM_X86_HVM_MONITOR_H__ */
 
diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 765d0b4..0ada970 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -83,7 +83,8 @@ static inline uint32_t arch_monitor_get_capabilities(struct domain *d)
                    (1U << XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST) |
                    (1U << XEN_DOMCTL_MONITOR_EVENT_DEBUG_EXCEPTION) |
                    (1U << XEN_DOMCTL_MONITOR_EVENT_CPUID) |
-                   (1U << XEN_DOMCTL_MONITOR_EVENT_INTERRUPT);
+                   (1U << XEN_DOMCTL_MONITOR_EVENT_INTERRUPT) |
+                   (1U << XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED);
 
     /* Since we know this is on VMX, we can just call the hvm func */
     if ( hvm_is_singlestep_supported() )
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index e2fd685..da7e4f8 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1007,6 +1007,7 @@ struct xen_domctl_psr_cmt_op {
 #define XEN_DOMCTL_MONITOR_EVENT_PRIVILEGED_CALL       7
 #define XEN_DOMCTL_MONITOR_EVENT_INTERRUPT             8
 #define XEN_DOMCTL_MONITOR_EVENT_DESC_ACCESS           9
+#define XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED    10
 
 struct xen_domctl_monitor_op {
     uint32_t op; /* XEN_DOMCTL_MONITOR_OP_* */
diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index f01e471..b531f71 100644
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -148,6 +148,8 @@
 #define VM_EVENT_REASON_INTERRUPT               12
 /* A descriptor table register was accessed. */
 #define VM_EVENT_REASON_DESCRIPTOR_ACCESS       13
+/* Current instruction is not implemented by the emulator */
+#define VM_EVENT_REASON_EMUL_UNIMPLEMENTED      14
 
 /* Supported values for the vm_event_write_ctrlreg index. */
 #define VM_EVENT_X86_CR0    0
-- 
2.7.4


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[PATCH v12 4/4] x86emul: Raise #UD when emulating an unrecognized instruction.

[Petre Pircalabu]

Modified the behavior of hvm_emulate_one_insn and
vmx_realmode_emulate_one to generate an Invalid Opcode trap when
X86EMUL_UNRECOGNIZED is returned by the emulator instead of just
crashing the domain.

Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
---
 xen/arch/x86/hvm/io.c           |  6 +++++-
 xen/arch/x86/hvm/vmx/realmode.c | 11 ++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index 7152c28..c7b1c53 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -96,10 +96,14 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, const char *descr)
     switch ( rc )
     {
     case X86EMUL_UNHANDLEABLE:
-    case X86EMUL_UNIMPLEMENTED:
         hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt, rc);
         return false;
 
+    case X86EMUL_UNRECOGNIZED:
+        hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt, rc);
+        hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
+        break;
+
     case X86EMUL_EXCEPTION:
         hvm_inject_event(&ctxt.ctxt.event);
         break;
diff --git a/xen/arch/x86/hvm/vmx/realmode.c b/xen/arch/x86/hvm/vmx/realmode.c
index b93792d..03dea6c 100644
--- a/xen/arch/x86/hvm/vmx/realmode.c
+++ b/xen/arch/x86/hvm/vmx/realmode.c
@@ -106,12 +106,21 @@ 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 || rc == X86EMUL_UNIMPLEMENTED )
+    if ( rc == X86EMUL_UNHANDLEABLE )
     {
         gdprintk(XENLOG_ERR, "Failed to emulate insn.\n");
         goto fail;
     }
 
+    if ( rc == X86EMUL_UNRECOGNIZED )
+    {
+        gdprintk(XENLOG_ERR, "Unrecognized insn.\n");
+        if ( curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PE )
+            goto fail;
+
+        realmode_deliver_exception(TRAP_invalid_op, 0, hvmemul_ctxt);
+    }
+
     if ( rc == X86EMUL_EXCEPTION )
     {
         if ( unlikely(curr->domain->debugger_attached) &&
-- 
2.7.4


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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Paul Durrant]

> -----Original Message-----
> From: Petre Pircalabu [mailto:ppircalabu@bitdefender.com]
> Sent: 21 September 2017 06:12
> To: xen-devel@lists.xen.org
> Cc: Ian Jackson <Ian.Jackson@citrix.com>; Wei Liu <wei.liu2@citrix.com>;
> Andrew Cooper <Andrew.Cooper3@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; jbeulich@suse.com; konrad.wilk@oracle.com;
> sstabellini@kernel.org; Tim (Xen.org) <tim@xen.org>; Paul Durrant
> <Paul.Durrant@citrix.com>; rcojocaru@bitdefender.com;
> tamas@tklengyel.com; jun.nakajima@intel.com; Kevin Tian
> <kevin.tian@intel.com>; Petre Pircalabu <ppircalabu@bitdefender.com>
> Subject: [PATCH v12 1/4] x86emul: New return code for unimplemented
> instruction
> 
> 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 returned by the core emulator only if it fails to
> properly decode the current instruction's opcode, and not by any of other
> functions, such as the x86_emulate_ops or the hvm_io_ops callbacks.
> 
> e.g. hvm_process_io_intercept should not return
> X86EMUL_UNIMPLEMENTED.
> The return value of this function depends on either the return code of
> one of the hvm_io_ops handlers (read/write) or the value returned by
> hvm_copy_guest_from_phys / hvm_copy_to_guest_phys.
> 
> Similary, none of this functions should return X86EMUL_UNIMPLEMENTED.
>  - hvm_io_intercept
>  - hvmemul_do_io
>  - hvm_send_buffered_ioreq
>  - hvm_send_ioreq
>  - hvm_broadcast_ioreq
>  - hvmemul_do_io_buffer
>  - hvmemul_validate
> 
> Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
> 
> ---
> Changed since v10:
>     * Added asserts to make sure the return code cannot be
> X86EMUL_UNIMPLEMENTED.
>     * Add new return code (X86EMUL_UNRECOGNIZED) to be used when
> trying
>     to emulate an instruction with an invalid opcode.
> 
> Changed since v11:
>     * Fixed double negative in the patch description.
>     * Move assertion into the switch and use ASSERT_UNREACHABLE() when
>     applicable.
>     * Changed the description of X86EMUL_UNIMPLEMENTED /
> X86EMUL_UNRECOGNIZED
>     to reflect the differences between those 2 return codes.
>     * Changed the returned value to X86EMUL_UNRECOGNIZED in the
>     following cases:
>         X86EMUL_OPC(0x0f, 0x73): /* Group 14 */
>         X86EMUL_OPC_66(0x0f, 0x73):
>         X86EMUL_OPC_VEX_66(0x0f, 0x73):
>                 - All valid opcodes are defined, so it should return
>                 X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
> 
>         X86EMUL_OPC(0x0f, 0xc7) /* Group 9 */
>                 - For register type instructions all possible opcodes are
>                 defined, so it should return X86EMUL_UNRECOGNIZED if
>                 mod R/M bits are not matched.
> 
>         X86EMUL_OPC_VEX(0x0f38, 0xf3): /* Group 17 */
>                 - All valid opcodes are defined, so it should return
>                 X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
> 
>         X86EMUL_OPC_XOP(09, 0x01): /* XOP Grp1 */
>         X86EMUL_OPC_XOP(09, 0x02): /* XOP Grp2 */
>                 - All valid opcodes are defined, so it should return
>                 X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
> 
>         X86EMUL_OPC(0x0f, 0x01): /* Grp7 */
>                 - Not all valid opcodes are defined so it should return
>                 X86EMUL_UNIMPLEMENTED if mod R/M bits are not matched.
>                 (e.g. XGETBV)
> 
>         X86EMUL_OPC_66(0x0f, 0x78):
>                 - All valid opcodes are defined, so it should return
>                 X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
> 
>         X86EMUL_OPC(0x0f, 0xae):
>         X86EMUL_OPC_66(0x0f, 0xae): /* Grp15 */
>                 - Not all valid opcodes are defined so it should return
>                 X86EMUL_UNIMPLEMENTED if mod R/M bits are not matched.
>                 (e.g. FXSAVE/FXRSTOR )
> ---
>  xen/arch/x86/hvm/emulate.c             | 12 ++++++++
>  xen/arch/x86/hvm/hvm.c                 |  1 +
>  xen/arch/x86/hvm/io.c                  |  1 +
>  xen/arch/x86/hvm/vmx/realmode.c        |  2 +-
>  xen/arch/x86/mm/shadow/multi.c         |  2 +-
>  xen/arch/x86/x86_emulate/x86_emulate.c | 52 ++++++++++++++++++++--
> ------------
>  xen/arch/x86/x86_emulate/x86_emulate.h | 13 +++++++++
>  7 files changed, 60 insertions(+), 23 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index cc874ce..385fe1e 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -284,10 +284,15 @@ static int hvmemul_do_io(
>          }
>          break;
>      }
> +    case X86EMUL_UNIMPLEMENTED:
> +        ASSERT_UNREACHABLE();
> +        /* Fall-through */

Kind of surprised you need the fall-through if you assert the code is unreachable... but analysis tools can be a bit temperamental so ok.

>      default:
>          BUG();
>      }
> 
> +    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> +

Isn't this assertion redundant given the ASSERT_UNREACHABLE() above?

  Paul

>      if ( rc != X86EMUL_OKAY )
>          return rc;
> 
> @@ -313,6 +318,9 @@ static int hvmemul_do_io_buffer(
> 
>      rc = hvmemul_do_io(is_mmio, addr, reps, size, dir, df, 0,
>                         (uintptr_t)buffer);
> +
> +    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> +
>      if ( rc == X86EMUL_UNHANDLEABLE && dir == IOREQ_READ )
>          memset(buffer, 0xff, size);
> 
> @@ -405,6 +413,8 @@ static int hvmemul_do_io_addr(
>      rc = hvmemul_do_io(is_mmio, addr, &count, size, dir, df, 1,
>                         ram_gpa);
> 
> +    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> +
>      if ( rc == X86EMUL_OKAY )
>          v->arch.hvm_vcpu.hvm_io.mmio_retry = (count < *reps);
> 
> @@ -2045,6 +2055,7 @@ int hvm_emulate_one_mmio(unsigned long mfn,
> unsigned long gla)
>      switch ( rc )
>      {
>      case X86EMUL_UNHANDLEABLE:
> +    case X86EMUL_UNIMPLEMENTED:
>          hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG",
> &ctxt);
>          break;
>      case X86EMUL_EXCEPTION:
> @@ -2102,6 +2113,7 @@ void hvm_emulate_one_vm_event(enum
> emul_kind kind, unsigned int trapnr,
>           * consistent with X86EMUL_RETRY.
>           */
>          return;
> +    case X86EMUL_UNIMPLEMENTED:
>      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/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 93394c1..43ff5aa 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3723,6 +3723,7 @@ void hvm_ud_intercept(struct cpu_user_regs
> *regs)
>      switch ( hvm_emulate_one(&ctxt) )
>      {
>      case X86EMUL_UNHANDLEABLE:
> +    case X86EMUL_UNIMPLEMENTED:
>          hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
>          break;
>      case X86EMUL_EXCEPTION:
> diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
> index bf41954..984db21 100644
> --- a/xen/arch/x86/hvm/io.c
> +++ b/xen/arch/x86/hvm/io.c
> @@ -96,6 +96,7 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t
> *validate, const char *descr)
>      switch ( rc )
>      {
>      case X86EMUL_UNHANDLEABLE:
> +    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 12d43ad..cf48139 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 8d4f244..2557e21 100644
> --- a/xen/arch/x86/mm/shadow/multi.c
> +++ b/xen/arch/x86/mm/shadow/multi.c
> @@ -3488,7 +3488,7 @@ 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 c1e2300..f334de9 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -848,7 +848,8 @@ do{ asm volatile (                                                      \
>                  stub.func);                                             \
>          generate_exception_if(res_.fields.trapnr == EXC_UD, EXC_UD);    \
>          domain_crash(current->domain);                                  \
> -        goto cannot_emulate;                                            \
> +        rc = X86EMUL_UNHANDLEABLE;                                      \
> +        goto done;                                                      \
>      }                                                                   \
>  } while (0)
>  #else
> @@ -2585,7 +2586,7 @@ x86_decode(
>                          d = twobyte_table[0x3a].desc;
>                          break;
>                      default:
> -                        rc = X86EMUL_UNHANDLEABLE;
> +                        rc = X86EMUL_UNRECOGNIZED;
>                          goto done;
>                      }
>                  }
> @@ -2599,7 +2600,7 @@ x86_decode(
>                  }
>                  else
>                  {
> -                    rc = X86EMUL_UNHANDLEABLE;
> +                    rc = X86EMUL_UNRECOGNIZED;
>                      goto done;
>                  }
> 
> @@ -2879,7 +2880,7 @@ x86_decode(
> 
>      default:
>          ASSERT_UNREACHABLE();
> -        return X86EMUL_UNHANDLEABLE;
> +        return X86EMUL_UNIMPLEMENTED;
>      }
> 
>      if ( ea.type == OP_MEM )
> @@ -4191,7 +4192,7 @@ x86_emulate(
>                  break;
>              case 4: /* fldenv - TODO */
>                  state->fpu_ctrl = true;
> -                goto cannot_emulate;
> +                goto unimplemented_insn;
>              case 5: /* fldcw m2byte */
>                  state->fpu_ctrl = true;
>                  if ( (rc = ops->read(ea.mem.seg, ea.mem.off, &src.val,
> @@ -4202,7 +4203,7 @@ x86_emulate(
>                  break;
>              case 6: /* fnstenv - TODO */
>                  state->fpu_ctrl = true;
> -                goto cannot_emulate;
> +                goto unimplemented_insn;
>              case 7: /* fnstcw m2byte */
>                  state->fpu_ctrl = true;
>                  emulate_fpu_insn_memdst("fnstcw", dst.val);
> @@ -4438,7 +4439,7 @@ x86_emulate(
>              case 4: /* frstor - TODO */
>              case 6: /* fnsave - TODO */
>                  state->fpu_ctrl = true;
> -                goto cannot_emulate;
> +                goto unimplemented_insn;
>              case 7: /* fnstsw m2byte */
>                  state->fpu_ctrl = true;
>                  emulate_fpu_insn_memdst("fnstsw", dst.val);
> @@ -5197,7 +5198,7 @@ x86_emulate(
>  #undef _GRP7
> 
>          default:
> -            goto cannot_emulate;
> +            goto unimplemented_insn;
>          }
>          break;
>      }
> @@ -6195,7 +6196,7 @@ x86_emulate(
>                  /* vpsll{w,d} $imm8,{x,y}mm,{x,y}mm */
>              break;
>          default:
> -            goto cannot_emulate;
> +            goto unimplemented_insn;
>          }
>      simd_0f_shift_imm:
>          generate_exception_if(ea.type != OP_REG, EXC_UD);
> @@ -6243,7 +6244,8 @@ x86_emulate(
>          case 6: /* psllq $imm8,mm */
>              goto simd_0f_shift_imm;
>          }
> -        goto cannot_emulate;
> +        rc = X86EMUL_UNRECOGNIZED;
> +        goto done;
> 
>      case X86EMUL_OPC_66(0x0f, 0x73):
>      case X86EMUL_OPC_VEX_66(0x0f, 0x73):
> @@ -6259,7 +6261,8 @@ x86_emulate(
>                  /* vpslldq $imm8,{x,y}mm,{x,y}mm */
>              goto simd_0f_shift_imm;
>          }
> -        goto cannot_emulate;
> +        rc = X86EMUL_UNRECOGNIZED;
> +        goto done;
> 
>      case X86EMUL_OPC(0x0f, 0x77):        /* emms */
>      case X86EMUL_OPC_VEX(0x0f, 0x77):    /* vzero{all,upper} */
> @@ -6323,7 +6326,8 @@ x86_emulate(
>          case 0: /* extrq $imm8,$imm8,xmm */
>              break;
>          default:
> -            goto cannot_emulate;
> +            rc = X86EMUL_UNRECOGNIZED;
> +            goto done;
>          }
>          /* fall through */
>      case X86EMUL_OPC_F2(0x0f, 0x78):     /* insertq $imm8,$imm8,xmm,xmm
> */
> @@ -6518,7 +6522,7 @@ x86_emulate(
>                  goto done;
>              break;
>          default:
> -            goto cannot_emulate;
> +            goto unimplemented_insn;
>          }
>          break;
> 
> @@ -6534,7 +6538,8 @@ x86_emulate(
>              vcpu_must_have(avx);
>              goto stmxcsr;
>          }
> -        goto cannot_emulate;
> +        rc = X86EMUL_UNRECOGNIZED;
> +        goto done;
> 
>      case X86EMUL_OPC_F3(0x0f, 0xae): /* Grp15 */
>          fail_if(modrm_mod != 3);
> @@ -6777,7 +6782,8 @@ x86_emulate(
>              switch ( modrm_reg & 7 )
>              {
>              default:
> -                goto cannot_emulate;
> +                rc = X86EMUL_UNRECOGNIZED;
> +                goto done;
> 
>  #ifdef HAVE_GAS_RDRAND
>              case 6: /* rdrand */
> @@ -7359,7 +7365,8 @@ x86_emulate(
>              host_and_vcpu_must_have(bmi1);
>              break;
>          default:
> -            goto cannot_emulate;
> +            rc = X86EMUL_UNRECOGNIZED;
> +            goto done;
>          }
> 
>          generate_exception_if(vex.l, EXC_UD);
> @@ -7670,7 +7677,8 @@ x86_emulate(
>              host_and_vcpu_must_have(tbm);
>              break;
>          default:
> -            goto cannot_emulate;
> +            rc = X86EMUL_UNRECOGNIZED;
> +            goto done;
>          }
> 
>      xop_09_rm_rv:
> @@ -7704,7 +7712,8 @@ x86_emulate(
>              host_and_vcpu_must_have(tbm);
>              goto xop_09_rm_rv;
>          }
> -        goto cannot_emulate;
> +        rc = X86EMUL_UNRECOGNIZED;
> +        goto done;
> 
>      case X86EMUL_OPC_XOP(0a, 0x10): /* bextr imm,r/m,r */
>      {
> @@ -7736,8 +7745,8 @@ x86_emulate(
>      }
> 
>      default:
> -    cannot_emulate:
> -        rc = X86EMUL_UNHANDLEABLE;
> +    unimplemented_insn:
> +        rc = X86EMUL_UNIMPLEMENTED;
>          goto done;
>      }
> 
> @@ -7789,7 +7798,8 @@ x86_emulate(
>                  if ( (d & DstMask) != DstMem )
>                  {
>                      ASSERT_UNREACHABLE();
> -                    goto cannot_emulate;
> +                    rc = X86EMUL_UNHANDLEABLE;
> +                    goto done;
>                  }
>                  break;
>              }
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h
> b/xen/arch/x86/x86_emulate/x86_emulate.h
> index 4ddf111..1fb74c0 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> @@ -133,6 +133,19 @@ 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 when a valid
> +  * opcode is found but the execution logic for that instruction is missing.
> +  * It should NOT be returned by any of the x86_emulate_ops callbacks.
> +  */
> +#define X86EMUL_UNIMPLEMENTED  5
> + /*
> +  * The current instruction's opcode is not valid.
> +  * If this error code is returned by a function, an #UD trap should be
> +  * raised by the final consumer of it.
> + */
> +#define X86EMUL_UNRECOGNIZED   X86EMUL_UNIMPLEMENTED
> 
>  /* FPU sub-types which may be requested via ->get_fpu(). */
>  enum x86_emulate_fpu_type {
> --
> 2.7.4


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Re: [PATCH v12 4/4] x86emul: Raise #UD when emulating an unrecognized instruction.

[Paul Durrant]

> -----Original Message-----
> From: Petre Pircalabu [mailto:ppircalabu@bitdefender.com]
> Sent: 21 September 2017 06:12
> To: xen-devel@lists.xen.org
> Cc: Ian Jackson <Ian.Jackson@citrix.com>; Wei Liu <wei.liu2@citrix.com>;
> Andrew Cooper <Andrew.Cooper3@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; jbeulich@suse.com; konrad.wilk@oracle.com;
> sstabellini@kernel.org; Tim (Xen.org) <tim@xen.org>; Paul Durrant
> <Paul.Durrant@citrix.com>; rcojocaru@bitdefender.com;
> tamas@tklengyel.com; jun.nakajima@intel.com; Kevin Tian
> <kevin.tian@intel.com>; Petre Pircalabu <ppircalabu@bitdefender.com>
> Subject: [PATCH v12 4/4] x86emul: Raise #UD when emulating an
> unrecognized instruction.
> 
> Modified the behavior of hvm_emulate_one_insn and
> vmx_realmode_emulate_one to generate an Invalid Opcode trap when
> X86EMUL_UNRECOGNIZED is returned by the emulator instead of just
> crashing the domain.
> 
> Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> ---
>  xen/arch/x86/hvm/io.c           |  6 +++++-
>  xen/arch/x86/hvm/vmx/realmode.c | 11 ++++++++++-
>  2 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
> index 7152c28..c7b1c53 100644
> --- a/xen/arch/x86/hvm/io.c
> +++ b/xen/arch/x86/hvm/io.c
> @@ -96,10 +96,14 @@ bool
> hvm_emulate_one_insn(hvm_emulate_validate_t *validate, const char
> *descr)
>      switch ( rc )
>      {
>      case X86EMUL_UNHANDLEABLE:
> -    case X86EMUL_UNIMPLEMENTED:
>          hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt, rc);
>          return false;
> 
> +    case X86EMUL_UNRECOGNIZED:
> +        hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt, rc);
> +        hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
> +        break;
> +
>      case X86EMUL_EXCEPTION:
>          hvm_inject_event(&ctxt.ctxt.event);
>          break;
> diff --git a/xen/arch/x86/hvm/vmx/realmode.c
> b/xen/arch/x86/hvm/vmx/realmode.c
> index b93792d..03dea6c 100644
> --- a/xen/arch/x86/hvm/vmx/realmode.c
> +++ b/xen/arch/x86/hvm/vmx/realmode.c
> @@ -106,12 +106,21 @@ 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 || rc == X86EMUL_UNIMPLEMENTED
> )
> +    if ( rc == X86EMUL_UNHANDLEABLE )

I don't quite understand this change. Why has it become unnecessary to deal with X86EMUL_UNIMPLEMENTED? Patch #1 added this change so it seems odd that patch #4 would then revert it.

  Paul

>      {
>          gdprintk(XENLOG_ERR, "Failed to emulate insn.\n");
>          goto fail;
>      }
> 
> +    if ( rc == X86EMUL_UNRECOGNIZED )
> +    {
> +        gdprintk(XENLOG_ERR, "Unrecognized insn.\n");
> +        if ( curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PE )
> +            goto fail;
> +
> +        realmode_deliver_exception(TRAP_invalid_op, 0, hvmemul_ctxt);
> +    }
> +
>      if ( rc == X86EMUL_EXCEPTION )
>      {
>          if ( unlikely(curr->domain->debugger_attached) &&
> --
> 2.7.4


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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Jan Beulich]

>>> On 21.09.17 at 07:12, <ppircalabu@bitdefender.com> wrote:
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -6195,7 +6196,7 @@ x86_emulate(
>                  /* vpsll{w,d} $imm8,{x,y}mm,{x,y}mm */
>              break;
>          default:
> -            goto cannot_emulate;
> +            goto unimplemented_insn;

I would really appreciate if you were a little more patient and waited
for replies to earlier review threads before sending a new version.
As said on the v11 thread, this ought to be "unrecognized".

> @@ -6243,7 +6244,8 @@ x86_emulate(
>          case 6: /* psllq $imm8,mm */
>              goto simd_0f_shift_imm;
>          }
> -        goto cannot_emulate;
> +        rc = X86EMUL_UNRECOGNIZED;
> +        goto done;

I think it would read better if we had an "unrecognized_insn"
label just like now we gain an "unimplemented_insn" one. Whether
the _insn suffixes are really useful is another question.

> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> @@ -133,6 +133,19 @@ 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 when a valid
> +  * opcode is found but the execution logic for that instruction is missing.
> +  * It should NOT be returned by any of the x86_emulate_ops callbacks.
> +  */
> +#define X86EMUL_UNIMPLEMENTED  5
> + /*
> +  * The current instruction's opcode is not valid.
> +  * If this error code is returned by a function, an #UD trap should be
> +  * raised by the final consumer of it.
> + */
> +#define X86EMUL_UNRECOGNIZED   X86EMUL_UNIMPLEMENTED

But with this aliasing of values the comment still is somewhat off.

Jan


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Re: [PATCH v12 4/4] x86emul: Raise #UD when emulating an unrecognized instruction.

[Jan Beulich]

>>> On 21.09.17 at 10:57, <Paul.Durrant@citrix.com> wrote:
>> From: Petre Pircalabu [mailto:ppircalabu@bitdefender.com]
>> Sent: 21 September 2017 06:12
>> --- a/xen/arch/x86/hvm/vmx/realmode.c
>> +++ b/xen/arch/x86/hvm/vmx/realmode.c
>> @@ -106,12 +106,21 @@ 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 || rc == X86EMUL_UNIMPLEMENTED
>> )
>> +    if ( rc == X86EMUL_UNHANDLEABLE )
> 
> I don't quite understand this change. Why has it become unnecessary to deal 
> with X86EMUL_UNIMPLEMENTED? Patch #1 added this change so it seems odd that 
> patch #4 would then revert it.

Yeah, it would certainly be more natural to bring things into
their final shape right away.

Jan


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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Jan Beulich]

>>> On 21.09.17 at 07:12, <ppircalabu@bitdefender.com> wrote:

> Changed since v11:
>     * Fixed double negative in the patch description.
>     * Move assertion into the switch and use ASSERT_UNREACHABLE() when
>     applicable.
>     * Changed the description of X86EMUL_UNIMPLEMENTED / X86EMUL_UNRECOGNIZED
>     to reflect the differences between those 2 return codes.
>     * Changed the returned value to X86EMUL_UNRECOGNIZED in the
>     following cases:
>         X86EMUL_OPC(0x0f, 0x73): /* Group 14 */
>         X86EMUL_OPC_66(0x0f, 0x73):
>         X86EMUL_OPC_VEX_66(0x0f, 0x73):
>                 - All valid opcodes are defined, so it should return
>                 X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
> 
>         X86EMUL_OPC(0x0f, 0xc7) /* Group 9 */
>                 - For register type instructions all possible opcodes are
>                 defined, so it should return X86EMUL_UNRECOGNIZED if
>                 mod R/M bits are not matched.

This is not entirely correct, btw (and hence the code change isn't
either): The code there has a dependency on gas features, so
hypervisor builds may not include support for rdrand and/or rdseed.
You will want to add "#else" cases producing "unimplemented".

Jan


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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Petre Ovidiu PIRCALABU]

On Thu, 2017-09-21 at 08:53 +0000, Paul Durrant wrote:
> >      }
> > +    case X86EMUL_UNIMPLEMENTED:
> > +        ASSERT_UNREACHABLE();
> > +        /* Fall-through */
>
> Kind of surprised you need the fall-through if you assert the code is
> unreachable... but analysis tools can be a bit temperamental so ok.
>
> >      default:
> >          BUG();
> >      }
> >
> > +    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> > +
>
> Isn't this assertion redundant given the ASSERT_UNREACHABLE() above?
>
>
> >   Paul

The second ASSERT statement is used to make sure the return value of
hvm_process_io_intercept or hvm_send_ioreq (called from the "case
X86EMUL_UNHANDLEABLE:" branch of the switch statement above) cannot
be X86EMUL_UNIMPLEMENTED.

> hvm_process_io_intercept
> >      if ( rc != X86EMUL_OKAY )
> >          return rc;
> >
> >
//Petre

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Re: [PATCH v12 4/4] x86emul: Raise #UD when emulating an unrecognized instruction.

[Petre Ovidiu PIRCALABU]

On Jo, 2017-09-21 at 06:44 -0600, Jan Beulich wrote:
> >
> > >
> > > >
> > > > On 21.09.17 at 10:57, <Paul.Durrant@citrix.com> wrote:
> > > From: Petre Pircalabu [mailto:ppircalabu@bitdefender.com]
> > > Sent: 21 September 2017 06:12
> > > --- a/xen/arch/x86/hvm/vmx/realmode.c
> > > +++ b/xen/arch/x86/hvm/vmx/realmode.c
> > > @@ -106,12 +106,21 @@ 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 || rc ==
> > > X86EMUL_UNIMPLEMENTED
> > > )
> > > +    if ( rc == X86EMUL_UNHANDLEABLE )
> > I don't quite understand this change. Why has it become unnecessary
> > to deal
> > with X86EMUL_UNIMPLEMENTED? Patch #1 added this change so it seems
> > odd that
> > patch #4 would then revert it.
> Yeah, it would certainly be more natural to bring things into
> their final shape right away.
>
> Jan
>
>
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Thank-you very much for your observation.
I will squash this patch into the first patch of the series. ("x86emul:
New return code for unimplemented instruction")

//Petre

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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Paul Durrant]

> -----Original Message-----
> From: Petre Ovidiu PIRCALABU [mailto:ppircalabu@bitdefender.com]
> Sent: 23 September 2017 19:57
> To: Paul Durrant <Paul.Durrant@citrix.com>; xen-devel@lists.xen.org
> Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>; Wei Liu
> <wei.liu2@citrix.com>; sstabellini@kernel.org; Ian Jackson
> <Ian.Jackson@citrix.com>; rcojocaru@bitdefender.com;
> konrad.wilk@oracle.com; George Dunlap <George.Dunlap@citrix.com>;
> Kevin Tian <kevin.tian@intel.com>; tamas@tklengyel.com;
> jbeulich@suse.com; jun.nakajima@intel.com; Tim (Xen.org) <tim@xen.org>
> Subject: Re: [PATCH v12 1/4] x86emul: New return code for unimplemented
> instruction
> 
> On Thu, 2017-09-21 at 08:53 +0000, Paul Durrant wrote:
> > >      }
> > > +    case X86EMUL_UNIMPLEMENTED:
> > > +        ASSERT_UNREACHABLE();
> > > +        /* Fall-through */
> >
> > Kind of surprised you need the fall-through if you assert the code is
> > unreachable... but analysis tools can be a bit temperamental so ok.
> >
> > >      default:
> > >          BUG();
> > >      }
> > >
> > > +    ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> > > +
> >
> > Isn't this assertion redundant given the ASSERT_UNREACHABLE() above?
> >
> >
> > >   Paul
> 
> The second ASSERT statement is used to make sure the return value of
> hvm_process_io_intercept or hvm_send_ioreq (called from the "case
> X86EMUL_UNHANDLEABLE:" branch of the switch statement above) cannot
> be X86EMUL_UNIMPLEMENTED.

Ah, ok. Just out of context in the patch.

  Paul

> 
> > hvm_process_io_intercept
> > >      if ( rc != X86EMUL_OKAY )
> > >          return rc;
> > >
> > >
> //Petre
> 
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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Petre Ovidiu PIRCALABU]

On Jo, 2017-09-21 at 06:42 -0600, Jan Beulich wrote:
> > 
> > > 
> > > > 
> > > > On 21.09.17 at 07:12, <ppircalabu@bitdefender.com> wrote:
> > --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> > +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> > @@ -6195,7 +6196,7 @@ x86_emulate(
> >                  /* vpsll{w,d} $imm8,{x,y}mm,{x,y}mm */
> >              break;
> >          default:
> > -            goto cannot_emulate;
> > +            goto unimplemented_insn;
> I would really appreciate if you were a little more patient and
> waited
> for replies to earlier review threads before sending a new version.
> As said on the v11 thread, this ought to be "unrecognized".
Thank-you very much for clearing this out. I will change the return
value to "unrecognized" in the next patchset iteration.

> 
> > 
> > @@ -6243,7 +6244,8 @@ x86_emulate(
> >          case 6: /* psllq $imm8,mm */
> >              goto simd_0f_shift_imm;
> >          }
> > -        goto cannot_emulate;
> > +        rc = X86EMUL_UNRECOGNIZED;
> > +        goto done;
> I think it would read better if we had an "unrecognized_insn"
> label just like now we gain an "unimplemented_insn" one. Whether
> the _insn suffixes are really useful is another question.

The best place to add this label is, in my opinion, at the end of the
"default" label of the "switch ( ctxt->opcode )" statement in
x86_emulate. This will make sure the current instruction flow will not
be altered.
e.g.:
     case X86EMUL_OPC_XOP(0a, 0x10): /* bextr imm,r/m,r */
     {
@@ -7750,6 +7742,9 @@ x86_emulate(
     unimplemented_insn:
         rc = X86EMUL_UNIMPLEMENTED;
         goto done;
+    unrecognized_insn:
+        rc = X86EMUL_UNRECOGNIZED;
+        goto done;
     }
Do you find this approach OK?
> 
> > 
> > --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> > +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> > @@ -133,6 +133,19 @@ 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 when a
> > valid
> > +  * opcode is found but the execution logic for that instruction
> > is missing.
> > +  * It should NOT be returned by any of the x86_emulate_ops
> > callbacks.
> > +  */
> > +#define X86EMUL_UNIMPLEMENTED  5
> > + /*
> > +  * The current instruction's opcode is not valid.
> > +  * If this error code is returned by a function, an #UD trap
> > should be
> > +  * raised by the final consumer of it.
> > + */
> > +#define X86EMUL_UNRECOGNIZED   X86EMUL_UNIMPLEMENTED
> But with this aliasing of values the comment still is somewhat off.

Do you think adding a "TODO:" comment can make things more clear?
e.g.:
   * The current instruction's opcode is not valid.
   * If this error code is returned by a function, an #UD trap should e
   * raised by the final consumer of it.
+  *
+  * TODO: For the moment X86EMUL_UNRECOGNIZED and 86EMUL_UNIMPLEMENTED
+  * can be used interchangeably.
  */

Many thanks for your support,
//Petre
> 
> Jan
> 
> 
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Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction

[Jan Beulich]

>>> On 25.09.17 at 11:16, <ppircalabu@bitdefender.com> wrote:
> @@ -7750,6 +7742,9 @@ x86_emulate(
>      unimplemented_insn:
>          rc = X86EMUL_UNIMPLEMENTED;
>          goto done;
> +    unrecognized_insn:
> +        rc = X86EMUL_UNRECOGNIZED;
> +        goto done;
>      }
> Do you find this approach OK?

Yes, that's reasonable I think.

> Do you think adding a "TODO:" comment can make things more clear?
> e.g.:
>    * The current instruction's opcode is not valid.
>    * If this error code is returned by a function, an #UD trap should e
>    * raised by the final consumer of it.
> +  *
> +  * TODO: For the moment X86EMUL_UNRECOGNIZED and 86EMUL_UNIMPLEMENTED
> +  * can be used interchangeably.
>   */

Something along these lines, yes, plus an indication that the #UD
raising therefore also isn't strictly being expected for now.

Jan


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