[PATCH 6/6] ARM: mm: truncate memory banks to fit in 4GB space for classic MMU

[Will Deacon]

On Tue, Mar 06, 2012 at 06:06:40PM +0000, Sergei Shtylyov wrote:
> Hello.

Hi Sergei,

> On 03/06/2012 07:54 PM, Will Deacon wrote:
> 
> > If a bank of memory spanning the 4GB boundary is added on a !CONFIG_LPAE
> > kernel then we will hang early during boot since the memory bank will
> > have wrapped around to zero.
> 
> > This patch truncates memory banks for !LPAE configurations when the end
> > address is not representable in 32 bits.
> 
> > Signed-off-by: Will Deacon<will.deacon at arm.com>
> > ---
> >   arch/arm/kernel/setup.c |   11 ++++++++++-
> >   1 files changed, 10 insertions(+), 1 deletions(-)
> 
> > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> > index a255c39..aeaa048 100644
> > --- a/arch/arm/kernel/setup.c
> > +++ b/arch/arm/kernel/setup.c
> > @@ -521,7 +521,16 @@ int __init arm_add_memory(phys_addr_t start, unsigned long size)
> >   	 */
> >   	size -= start&  ~PAGE_MASK;
> >   	bank->start = PAGE_ALIGN(start);
> > -	bank->size  = size&  PAGE_MASK;
> > +
> > +#ifndef CONFIG_LPAE
> > +	if (bank->start + size<  bank->start) {
> > +		printk(KERN_CRIT "Truncating memory at 0x%08llx to fit in "
> > +			"32-bit physical address space\n", (long long)start);
> > +		size = ULONG_MAX - bank->start;
> 
>     I think you forgot to add one here.

No, I deliberately omit the last page because otherwise we end up with the
end address of the bank being calculated as 0, which leads to boot failure.

Will