Re: [Qemu-devel] [PATCH v4 11/43] tcg: define CF_PARALLEL and use it for TB hashing along with CF_COUNT_MASK

["Emilio G. Cota" <cota@braap.org>]

Hi Richard,

Are you planning to get this patchset merged in this window? If so, I can
give it a respin on top of the current master.

Anyway, before doing so we should fix the issue around CF_COUNT_MASK that
Pranith reported:

On Wed, Aug 30, 2017 at 10:43:28 -0400, Pranith Kumar wrote:
> On Tue, Aug 29, 2017 at 5:16 PM, Emilio G. Cota <cota@braap.org> wrote:
> > On Sun, Aug 27, 2017 at 18:15:50 -0400, Pranith Kumar wrote:
> >> Hi Emilio,
> >>
> >> On Fri, Jul 21, 2017 at 1:59 AM, Emilio G. Cota <cota@braap.org> wrote:
> >> > This will enable us to decouple code translation from the value
> >> > of parallel_cpus at any given time. It will also help us minimize
> >> > TB flushes when generating code via EXCP_ATOMIC.
> >> >
> >> > Note that the declaration of parallel_cpus is brought to exec-all.h
> >> > to be able to define there the "curr_cflags" inline.
> >> >
> >> > Signed-off-by: Emilio G. Cota <cota@braap.org>
> >>
> >> I was testing a winxp image today and I bisected a infinite loop to
> >> this commit. The loop happens both with and without mttcg, so I think
> >> it has got to do with something else.
> >
> > Can you test the below? It lets me boot ubuntu, otherwise it reliably
> > chokes on a 'rep movsb' *very* early (doesn't even get to grub).
> >
> > This discusson on v2 might be relevant (I added CF_COUNT_MASK as a
> > result of it, but it seems I have to revisit that):
> >   https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg06456.html
> >
> > Anyway let me know if this fixes it for you. Thanks for testing!
> >
> 
> Yes, this fixes the issue for me.

My quick-fix is just not to check those bits, but as you pointed out during
v3's review the whole thing is a little bit fragile if we don't check them.

Should we just go with the CF_NOCHAIN flag that you proposed? If so, do you
want me to give that approach a go, or you prefer to do it yourself?

Thanks,

		Emilio