linux-kernel - Re: [PATCH] ARM: memblock limit must be pmd-aligned

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Date:   Tue, 27 Jun 2017 18:14:45 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Doug Berger <opendmb@...il.com>
Cc:     Laura Abbott <labbott@...hat.com>, linux@...linux.org.uk,
        nicolas.pitre@...aro.org, tixy@...aro.org, f.fainelli@...il.com,
        keescook@...omium.org, ard.biesheuvel@...aro.org,
        marc.zyngier@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: memblock limit must be pmd-aligned

On Tue, Jun 27, 2017 at 09:57:17AM -0700, Doug Berger wrote:
> On 06/27/2017 03:59 AM, Mark Rutland wrote:
> > On Mon, Jun 26, 2017 at 05:50:03PM -0700, Doug Berger wrote:
> >> On 06/26/2017 04:43 PM, Laura Abbott wrote:
> >>> On 06/26/2017 10:23 AM, Doug Berger wrote:
> >>>> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> >>>> index 31af3cb59a60..2ae4f9c9d757 100644
> >>>> --- a/arch/arm/mm/mmu.c
> >>>> +++ b/arch/arm/mm/mmu.c
> >>>> @@ -1226,7 +1226,7 @@ void __init adjust_lowmem_bounds(void)
> >>>>  	if (memblock_limit)
> >>>>  		memblock_limit = round_down(memblock_limit, PMD_SIZE);
> >>>>  	if (!memblock_limit)
> >>>> -		memblock_limit = arm_lowmem_limit;
> >>>> +		memblock_limit = round_down(arm_lowmem_limit, PMD_SIZE);
> >>>>  
> > 
> > Given we're always going to do the rounding, how about we move that out
> > of the existing conditional, i.e. get rid of the first if, and have:
> > 
> > 	if (!memblock_limit)
> > 		memblock_limit = arm_lowmem_limit;
> > 
> > 	/*
> > 	 * Round the memblock limit down to a pmd size.  This
> > 	 * helps to ensure that we will allocate memory from the
> > 	 * last full pmd, which should be mapped.
> > 	 */
> > 	memblock_limit = round_down(memblock_limit, PMD_SIZE);
> > 
> > Thanks,
> > Mark.
> That makes perfect sense to me.  I will submit a v2 with this code
> change.  Should I add your Signed-off-by since it is your change?

Since you're writing the patch, there's no need.

Feel free to add my Suggested-by if you want, but I'm not too worried
either way.

Thanks,
Mark.