Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page

[Christophe Leroy]

Le 31/01/2020 Ã 20:38, Segher Boessenkool a ÃcritÂ:
> On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
> > Le 31/01/2020 Ã 16:51, Segher Boessenkool a ÃcritÂ:
> > > On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
> > > > When the range is a single page, do a page flush instead.
> > >
> > > > +	start &= PAGE_MASK;
> > > > +	end = (end - 1) | ~PAGE_MASK;
> > > >   	if (!Hash) {
> > > > -		_tlbia();
> > > > +		if (end - start == PAGE_SIZE)
> > > > +			_tlbie(start);
> > > > +		else
> > > > +			_tlbia();
> > > >   		return;
> > > >   	}
> > >
> > > For just one page, you get  end - start == 0  actually?
> >
> > Oops, good catch.
> >
> > Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
>
> You have all low bits masked off in both start and end, so you get zero.
> You could make the condion read "if (start == end)?

No, in end the low bits are set, that's a BIT OR with ~PAGE_MASK, so it 
sets all low bits to 1.

Christophe