Re: [Qemu-devel] [PATCH 1/2] target-i386: tcg: Accept clwb instruction

[Eduardo Habkost]

On Fri, Nov 06, 2015 at 12:04:56PM +0100, Richard Henderson wrote:
> On 11/04/2015 10:24 PM, Eduardo Habkost wrote:
> >Accept the clwb instruction (66 0F AE /6) if its corresponding feature
> >flag is enabled on CPUID[7].
> >
> >Signed-off-by: Eduardo Habkost <address@hidden>
> >---
> >  target-i386/translate.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> >
> >diff --git a/target-i386/translate.c b/target-i386/translate.c
> >index b400d24..bac1685 100644
> >--- a/target-i386/translate.c
> >+++ b/target-i386/translate.c
> >@@ -7716,10 +7716,21 @@ static target_ulong disas_insn(CPUX86State *env, 
> >DisasContext *s,
> >              }
> >              break;
> >          case 5: /* lfence */
> >-        case 6: /* mfence */
> >              if ((modrm & 0xc7) != 0xc0 || !(s->cpuid_features & 
> > CPUID_SSE2))
> >                  goto illegal_op;
> >              break;
> >+        case 6: /* mfence/clwb */
> >+            if (s->prefix & PREFIX_DATA) {
> >+                /* clwb */
> >+                if (!(s->cpuid_7_0_ebx_features & CPUID_7_0_EBX_CLWB))
> >+                    goto illegal_op;
> >+                gen_lea_modrm(env, s, modrm);
> 
> You should use gen_nop_modrm here, since we're not going to do anything with
> the address.  Otherwise,
> 
> Reviewed-by: Richard Henderson <address@hidden>

Thanks! BTW, clflush uses gen_lea_modrm() too, does it do anything with
the address somewhere else?

-- 
Eduardo