Re: [PATCH] powerpc/mm: fix a hardcode on memory boundary checking

[Rui Teng]

On 31/01/2017 5:11 PM, Michael Ellerman wrote:
> Rui Teng <rui.teng@xxxxxxxxxxxxxxxxxx> writes:
>
> > The offset of hugepage block will not be 16G, if the expected
> > page is more than one. Calculate the totol size instead of the
> > hardcode value.
>
> I assume you found this by code inspection and not by triggering an
> actual bug?

Yes, I found this problem only by code inspection. We were finding the
ways to enable 16G huge page besides changing the device tree. For 
example, provide a new interface to set these size and pages parameters.
So that I think it may cause problem here.

> cheers
>
> > diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> > index 8033493..b829f8e 100644
> > --- a/arch/powerpc/mm/hash_utils_64.c
> > +++ b/arch/powerpc/mm/hash_utils_64.c
> > @@ -506,7 +506,7 @@ static int __init htab_dt_scan_hugepage_blocks(unsigned long node,
> >  	printk(KERN_INFO "Huge page(16GB) memory: "
> >  			"addr = 0x%lX size = 0x%lX pages = %d\n",
> >  			phys_addr, block_size, expected_pages);
> > -	if (phys_addr + (16 * GB) <= memblock_end_of_DRAM()) {
> > +	if (phys_addr + block_size * expected_pages <= memblock_end_of_DRAM()) {
> >  		memblock_reserve(phys_addr, block_size * expected_pages);
> >  		add_gpage(phys_addr, block_size, expected_pages);
> >  	}
> > --
> > 2.9.0