Re: [PATCH V4 1/1] target/loongarch: Fixed tlb huge page loading issue

[Richard Henderson]

On 3/14/24 23:01, lixianglai wrote:
> Hi Richard :
>
> > On 3/14/24 20:22, lixianglai wrote:
> > > Hi Richard:
> > > > On 3/13/24 15:33, Xianglai Li wrote:
> > > > > +    if (unlikely((level == 0) || (level > 4))) {
> > > > > +        return base;
> > > > > +    }
> > ...
> > > > Perhaps it would be worthwhile to add another for the level==0 or > 4 case 
> > > > above?
> > > A normal level 4 page table should not print an error log,
> > >
> > > only if a level 4 page is large, so we should put it in
> > >
> > >      if (FIELD_EX64(base, TLBENTRY, HUGE)) {
> > >          if (unlikely(level == 4)) {
> > >              qemu_log_mask(LOG_GUEST_ERROR,
> > >                            "Attempted use of level %lu huge page\n", level);
> > >          }
> > >
> > >          if (FIELD_EX64(base, TLBENTRY, LEVEL)) {
> > >              return base;
> > >          } else {
> > >              return  FIELD_DP64(base, TLBENTRY, LEVEL, level);
> > >          }
> > >      }
> >
> > A level 5 page table is not normal, nor is a level 0 lddir.
>
> We communicate with the hardware guys that the behavior above level 4 and lddir 0 is 
> undefined behavior.
>
> The result of our test on 3A5000 is that it has no any effect on "base",
>
> however in future chips the behavior may change since it may support 5-level page table 
> and width for level[13:14] may change also.
>
>
> So in this context,I am not sure which level to use to print logs,
>
> which content to print, and where to add these prints,
>
> any more detailed advice?

Yes, right there in the IF that I quoted at the top.
What I was trying to spell out is

    if (unlikely(level == 0 || level > 4)) {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "Attepted LDDIR with level %"PRId64"\n", level);
        return base;
    }


r~