linux-kernel - Re: [PATCH RFC 2/2] ARM: nommu: remap exception base address to RAM

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Date:   Wed, 14 Dec 2016 00:05:47 +0530
From:   Afzal Mohammed <afzal.mohd.ma@...il.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Vladimir Murzin <vladimir.murzin@....com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 2/2] ARM: nommu: remap exception base address to RAM

Hi,

On Tue, Dec 13, 2016 at 10:02:26AM +0000, Russell King - ARM Linux wrote:
> On Sun, Dec 11, 2016 at 06:42:55PM +0530, Afzal Mohammed wrote:

> >  	bic	r0, r0, #CR_V
> >  #endif
> >  	mcr	p15, 0, r0, c1, c0, 0		@ write control reg
> > +
> > +#ifdef CONFIG_REMAP_VECTORS_TO_RAM
> > +	mov	r3, #CONFIG_VECTORS_BASE	@ read VECTORS_BASE
> > +	mcr	p15, 0, r3, c12, c0, 0		@ write to VBAR
> > +#endif
> > +

> Is there really any need to do this in head.S ?

Seeing the high vector configuration done here, pounced upon it :)

> I believe it's
> entirely possible to do it later - arch/arm/mm/nommu.c:paging_init().
> 
> Also, if the region setup for the vectors was moved as well, it would
> then be possible to check the ID registers to determine whether this
> is supported, and make the decision where to locate the vectors base
> more dynamically.

i will look into it.

Regards
afzal