Re: [regression] Boot crash with: f7426b983a6a ("mm: cma: adjust address limit to avoid hitting low/high memory boundary")
From: Joonsoo Kim
Date: Wed Dec 10 2014 - 02:13:37 EST
On Tue, Dec 09, 2014 at 08:50:32AM +0000, Russell King wrote:
> On Tue, Dec 09, 2014 at 04:55:42PM +0900, Joonsoo Kim wrote:
> > Could you manage this fix for above boot regression in x86?
> > Patch itself is so dirty, because __pa_nodebug() is implemented only
> > in x86. If someone knows better idea, please let me know.
> > +#ifdef CONFIG_X86
> > + /*
> > + * high_memory isn't direct mapped memory so retrieving it's
> > + * physical address isn't appropriate. But, it would be useful
> > + * to check physical address of highmem boundary so it's
> > + * justfiable to get physical address from it. In x86, there is
> > + * a validation check for this case, so following workaround is
> > + * needed to avoid it.
> > + */
> > + highmem_start = __pa_nodebug(high_memory);
> > +#else
> > + highmem_start = __pa(high_memory);
> > +#endif
> What about:
> highmem_start = __pa(high_memory - 1) + 1;
> As "high_memory - 1" should be a valid lowmem address.
Thanks for suggestion.
It looks tricky but it would work. I think that this one need to be
fully tested, so the first dirty one is better for the stable tree.
I will check and test Russell's suggestion and send it as clean-up.
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