Re: [PATCH] accel/tcg: nochain should disable goto_ptr

[Richard Henderson]

On 6/1/24 00:57, niugen wrote:
> on 2024/6/1 01:32, Richard Henderson wrote:
> > On 5/31/24 03:17, NiuGenen wrote:
> > > Signed-off-by: NiuGenen <niugen@loongson.cn>
> > > ---
> > >   accel/tcg/cpu-exec.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> > > index 2972f75b96..084fa645c7 100644
> > > --- a/accel/tcg/cpu-exec.c
> > > +++ b/accel/tcg/cpu-exec.c
> > > @@ -173,7 +173,7 @@ uint32_t curr_cflags(CPUState *cpu)
> > >       } else if (qatomic_read(&one_insn_per_tb)) {
> > >           cflags |= CF_NO_GOTO_TB | 1;
> > >       } else if (qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
> > > -        cflags |= CF_NO_GOTO_TB;
> > > +        cflags |= CF_NO_GOTO_TB | CF_NO_GOTO_PTR;
> > >       }
> > >         return cflags;
> >
> > Why?
> >
> > The original intent of nochain was so that -d exec would log all blocks, which requires 
> > excluding goto_tb.  There is exec logging in helper_lookup_goto_ptr, so there is no need 
> > to avoid goto_ptr.
> >
> > You must provide a rationale, at minimum.
> >
> >
> > r~
>
>
> Sorry, my mistake. I thought nochain will disable all kinds of branches, including direct 
> branch and indirect branch, but I found that indirect branch still call 
> helper_lookup_tb_ptr to continue executing TB instead of epilogue-tblookup-prologue.
>
> Maybe the exec logging can be removed from helper_lookup_tb_ptr and nochain can disable 
> all the chaining of TB?

Why?  You still haven't provided a rationale.


r~