linux-kernel - Re: [PATCH v2 16/22] ARM: mm: cleanup checks for membank overlap with vmalloc area

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Message-ID: <alpine.LFD.2.02.1209101406510.28681@xanadu.home>
Date:	Mon, 10 Sep 2012 14:07:34 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Cyril Chemparathy <cyril@...com>
cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	arnd@...db.de, catalin.marinas@....com, grant.likely@...retlab.ca,
	linux@....linux.org.uk, will.deacon@....com,
	Vitaly Andrianov <vitalya@...com>
Subject: Re: [PATCH v2 16/22] ARM: mm: cleanup checks for membank overlap
 with vmalloc area

On Mon, 10 Sep 2012, Cyril Chemparathy wrote:

> On 8/12/2012 12:36 AM, Nicolas Pitre wrote:
> > On Fri, 10 Aug 2012, Cyril Chemparathy wrote:
> > 
> > > On Keystone platforms, physical memory is entirely outside the 32-bit
> > > addressible range.  Therefore, the (bank->start > ULONG_MAX) check below
> > > marks
> > > the entire system memory as highmem, and this causes unpleasentness all
> > > over.
> > > 
> > > This patch eliminates the extra bank start check (against ULONG_MAX) by
> > > checking bank->start against the physical address corresponding to
> > > vmalloc_min
> > > instead.
> > > 
> > > In the process, this patch also cleans up parts of the highmem sanity
> > > check
> > > code by removing what has now become a redundant check for banks that
> > > entirely
> > > overlap with the vmalloc range.
> > 
> > Are you sure of this?  The code that you removed not only checks for
> > banks that fall into the vmalloc area, but it also skipp them.  This is
> > now lost.
> > 
> 
> I almost missed out on this email...
> 
> The check is not quite lost, we still have the following in the
> !CONFIG_HIGHMEM block:
> 
> 	if (highmem) {
> 		printk(...);
> 		continue;
> 	}
> 
> The change is that highmem is now set outside the #ifdef when (bank->start >=
> vmalloc_limit), and therefore the check is truly redundant.

OK.

Acked-by: Nicolas Pitre <nico@...aro.org>



> 
> > > Signed-off-by: Cyril Chemparathy <cyril@...com>
> > > Signed-off-by: Vitaly Andrianov <vitalya@...com>
> > > ---
> > >   arch/arm/mm/mmu.c |   19 +------------------
> > >   1 file changed, 1 insertion(+), 18 deletions(-)
> > > 
> > > diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> > > index f764c03..3d685c6 100644
> > > --- a/arch/arm/mm/mmu.c
> > > +++ b/arch/arm/mm/mmu.c
> > > @@ -901,15 +901,12 @@ void __init sanity_check_meminfo(void)
> > >   		struct membank *bank = &meminfo.bank[j];
> > >   		*bank = meminfo.bank[i];
> > > 
> > > -		if (bank->start > ULONG_MAX)
> > > -			highmem = 1;
> > > -
> > > -#ifdef CONFIG_HIGHMEM
> > >   		if (bank->start >= vmalloc_limit)
> > >   			highmem = 1;
> > > 
> > >   		bank->highmem = highmem;
> > > 
> > > +#ifdef CONFIG_HIGHMEM
> > >   		/*
> > >   		 * Split those memory banks which are partially overlapping
> > >   		 * the vmalloc area greatly simplifying things later.
> > > @@ -932,8 +929,6 @@ void __init sanity_check_meminfo(void)
> > >   			bank->size = vmalloc_limit - bank->start;
> > >   		}
> > >   #else
> > > -		bank->highmem = highmem;
> > > -
> > >   		/*
> > >   		 * Highmem banks not allowed with !CONFIG_HIGHMEM.
> > >   		 */
> > > @@ -946,18 +941,6 @@ void __init sanity_check_meminfo(void)
> > >   		}
> > > 
> > >   		/*
> > > -		 * Check whether this memory bank would entirely overlap
> > > -		 * the vmalloc area.
> > > -		 */
> > > -		if (bank->start >= vmalloc_limit) {
> > > -			printk(KERN_NOTICE "Ignoring RAM at %.8llx-%.8llx "
> > > -			       "(vmalloc region overlap).\n",
> > > -			       (unsigned long long)bank->start,
> > > -			       (unsigned long long)bank->start + bank->size -
> > > 1);
> > > -			continue;
> > > -		}
> > > -
> > > -		/*
> > >   		 * Check whether this memory bank would partially overlap
> > >   		 * the vmalloc area.
> > >   		 */
> > > --
> > > 1.7.9.5
> > > 
> 
> -- 
> Thanks
> - Cyril
> 
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