When CR0.TS=1, execution of x87 FPU, MMX, and some SSE instructions will
cause a Device Not Available (DNA) exception (#NM). System software uses
this exception event to lazily context switch FPU state.
Before this patch, enter_mmx helpers may be generated just before #NM
generation, prematurely resetting FPU state before the guest has a
chance to save it.
Signed-off-by: Matt Borgerson <contact@mborgerson.com>
---
target/i386/tcg/decode-new.c.inc | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.c.inc
index 46afd9960b..0ead1c6011 100644
--- a/target/i386/tcg/decode-new.c.inc
+++ b/target/i386/tcg/decode-new.c.inc
@@ -1803,16 +1803,19 @@ static void disas_insn_new(DisasContext *s,
CPUState *cpu, int b)
}
break;
- case X86_SPECIAL_MMX:
- if (!(s->prefix & (PREFIX_REPZ | PREFIX_REPNZ | PREFIX_DATA))) {
- gen_helper_enter_mmx(cpu_env);
- }
+ default:
break;
}
if (!validate_vex(s, &decode)) {
return;
}
+
+ if (decode.e.special == X86_SPECIAL_MMX &&
+ !(s->prefix & (PREFIX_REPZ | PREFIX_REPNZ | PREFIX_DATA))) {
+ gen_helper_enter_mmx(cpu_env);
+ }
+
if (decode.op[0].has_ea || decode.op[1].has_ea || decode.op[2].has_ea) {
gen_load_ea(s, &decode.mem, decode.e.vex_class == 12);
}
--
2.34.1