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@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
xen-unstable changeset:   24417:1452fb248cd5
xen-unstable date:        Fri Dec 16 15:45:40 2011 +0100

4 files changed, 17 insertions, 1 deletions

diff --git a/tools/tests/x86_emulator/x86_emulate.c b/tools/tests/x86_emulator/x86_emulate.c
index a58a7b8178..95e9ff603d 100644
--- a/tools/tests/x86_emulator/x86_emulate.c
+++ b/tools/tests/x86_emulator/x86_emulate.c
@@ -3,5 +3,7 @@
 #include <string.h>
 #include <public/xen.h>
 
+#define cpu_has_amd_erratum(nr) 0
+
 #include "x86_emulate/x86_emulate.h"
 #include "x86_emulate/x86_emulate.c"
diff --git a/xen/arch/x86/x86_emulate.c b/xen/arch/x86/x86_emulate.c
index fbf740efee..91f524fc87 100644
--- a/xen/arch/x86/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate.c
@@ -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 --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index aa491f1de4..c070656a30 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2578,6 +2578,9 @@ x86_emulate(
     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 */
@@ -2603,7 +2606,6 @@ x86_emulate(
         case 0xf8: /* fprem */
         case 0xf9: /* fyl2xp1 */
         case 0xfa: /* fsqrt */
-        case 0xfb: /* fsincos */
         case 0xfc: /* frndint */
         case 0xfd: /* fscale */
         case 0xfe: /* fsin */
diff --git a/xen/include/asm-x86/amd.h b/xen/include/asm-x86/amd.h
index 283c172074..708fed2fd2 100644
--- a/xen/include/asm-x86/amd.h
+++ b/xen/include/asm-x86/amd.h
@@ -138,6 +138,12 @@
     AMD_OSVW_ERRATUM(1, AMD_MODEL_RANGE(0xf, 0x41, 0x2, 0xff, 0xf),     \
                         AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0xff, 0xf))
 
+#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, ...);