Re: [Qemu-devel] [PATCH 05/10] tcg: Prepare TB invalidation for lockless TB lookup

[Paolo Bonzini]

----- Original Message -----
> From: "Sergey Fedorov" <address@hidden>
> To: "Paolo Bonzini" <address@hidden>, address@hidden
> Cc: "sergey fedorov" <address@hidden>, "alex bennee" <address@hidden>
> Sent: Tuesday, July 19, 2016 9:56:49 PM
> Subject: Re: [PATCH 05/10] tcg: Prepare TB invalidation for lockless TB lookup
> 
> On 19/07/16 11:32, Paolo Bonzini wrote:
> >
> 
> It looks much better now :)
> 
> > When invalidating a translation block, set an invalid flag into the
> > TranslationBlock structure first.  It is also necessary to check whether
> > the target TB is still valid after acquiring 'tb_lock' but before calling
> > tb_add_jump() since TB lookup is to be performed out of 'tb_lock' in
> > future. Note that we don't have to check 'last_tb'; an already invalidated
> > TB will not be executed anyway and it is thus safe to patch it.
> >
> > Suggested-by: Sergey Fedorov <address@hidden>
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > ---
> >  cpu-exec.c              | 5 +++--
> >  include/exec/exec-all.h | 2 ++
> >  translate-all.c         | 3 +++
> >  3 files changed, 8 insertions(+), 2 deletions(-)
> (snip)
> > diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> > index acda7b6..bc0bcc5 100644
> > --- a/include/exec/exec-all.h
> > +++ b/include/exec/exec-all.h
> > @@ -213,6 +213,8 @@ struct TranslationBlock {
> >  #define CF_USE_ICOUNT  0x20000
> >  #define CF_IGNORE_ICOUNT 0x40000 /* Do not generate icount code */
> >  
> > +    uint16_t invalid;
> 
> Why not "int"?

There's a hole there, we may want to move something else so I
used a smaller data type.  Even uint8_t would do.

Paolo
> 
> > +
> >      void *tc_ptr;    /* pointer to the translated code */
> >      uint8_t *tc_search;  /* pointer to search data */
> >      /* original tb when cflags has CF_NOCACHE */
> >
> 
> Thanks,
> Sergey
>