[Xen-changelog] [xen-unstable] x86/emulator: workaround for AMD erratum 573

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1324046740 -3600
# Node ID 1452fb248cd513832cfbbd1100b9b72a0dde7ea6
# Parent  01c8b27e3d7d4ad2b469be9922bb04b5eb0195e8
x86/emulator: workaround for AMD erratum 573

The only cases where we might end up emulating fsincos (as any other
x87 operations without memory operands) are
- when a HVM guest is in real mode (not applicable on AMD)
- between two half page table updates in PAE mode (unlikely, and not
  doing the emulation here does affect only performance, not
  correctness)
- when a guest maliciously (or erroneously) modifies an (MMIO or page
  table update) instruction under emulation (unspecified behavior)

Hence, in order to avoid the erratum to cause harm to the entire host,
don't emulate fsincos on the affected AMD CPU families.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
---


diff -r 01c8b27e3d7d -r 1452fb248cd5 tools/tests/x86_emulator/x86_emulate.c
--- a/tools/tests/x86_emulator/x86_emulate.c    Thu Dec 15 16:56:21 2011 +0000
+++ b/tools/tests/x86_emulator/x86_emulate.c    Fri Dec 16 15:45:40 2011 +0100
@@ -9,5 +9,7 @@
 
 #define BUG() abort()
 
+#define cpu_has_amd_erratum(nr) 0
+
 #include "x86_emulate/x86_emulate.h"
 #include "x86_emulate/x86_emulate.c"
diff -r 01c8b27e3d7d -r 1452fb248cd5 xen/arch/x86/x86_emulate.c
--- a/xen/arch/x86/x86_emulate.c        Thu Dec 15 16:56:21 2011 +0000
+++ b/xen/arch/x86/x86_emulate.c        Fri Dec 16 15:45:40 2011 +0100
@@ -10,8 +10,14 @@
  */
 
 #include <asm/x86_emulate.h>
+#include <asm/processor.h> /* current_cpu_info */
+#include <asm/amd.h> /* cpu_has_amd_erratum() */
 
 /* Avoid namespace pollution. */
 #undef cmpxchg
+#undef cpuid
+
+#define cpu_has_amd_erratum(nr) \
+        cpu_has_amd_erratum(&current_cpu_data, AMD_ERRATUM_##nr)
 
 #include "x86_emulate/x86_emulate.c"
diff -r 01c8b27e3d7d -r 1452fb248cd5 xen/arch/x86/x86_emulate/x86_emulate.c
--- a/xen/arch/x86/x86_emulate/x86_emulate.c    Thu Dec 15 16:56:21 2011 +0000
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c    Fri Dec 16 15:45:40 2011 +0100
@@ -2761,6 +2761,9 @@
     case 0xd9: /* FPU 0xd9 */
         switch ( modrm )
         {
+        case 0xfb: /* fsincos */
+            fail_if(cpu_has_amd_erratum(573));
+            /* fall through */
         case 0xc0 ... 0xc7: /* fld %stN */
         case 0xc8 ... 0xcf: /* fxch %stN */
         case 0xd0: /* fnop */
@@ -2786,7 +2789,6 @@
         case 0xf8: /* fprem */
         case 0xf9: /* fyl2xp1 */
         case 0xfa: /* fsqrt */
-        case 0xfb: /* fsincos */
         case 0xfc: /* frndint */
         case 0xfd: /* fscale */
         case 0xfe: /* fsin */
diff -r 01c8b27e3d7d -r 1452fb248cd5 xen/include/asm-x86/amd.h
--- a/xen/include/asm-x86/amd.h Thu Dec 15 16:56:21 2011 +0000
+++ b/xen/include/asm-x86/amd.h Fri Dec 16 15:45:40 2011 +0100
@@ -134,6 +134,12 @@
     AMD_OSVW_ERRATUM(3, AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0xff, 0xf),    \
                        AMD_MODEL_RANGE(0x12, 0x0, 0x0, 0x1, 0x0))
 
+#define AMD_ERRATUM_573                                                        
\
+    AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x0f, 0x0, 0x0, 0xff, 0xf),     \
+                       AMD_MODEL_RANGE(0x10, 0x0, 0x0, 0xff, 0xf),     \
+                       AMD_MODEL_RANGE(0x11, 0x0, 0x0, 0xff, 0xf),     \
+                       AMD_MODEL_RANGE(0x12, 0x0, 0x0, 0xff, 0xf))
+
 struct cpuinfo_x86;
 int cpu_has_amd_erratum(const struct cpuinfo_x86 *, int, ...);
 

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