RE: [PATCH] [RESEND] arm: limit memblock base address for early_pte_alloc

Kim, Jong-Sung
2012-06-28T06:08:50Z

> From: Russell King - ARM Linux [mailto:linux@arm.linux.org.uk]
> Sent: Thursday, June 28, 2012 4:18 AM
> On Fri, Jun 08, 2012 at 10:58:50PM +0900, Kim, Jong-Sung wrote:
> >
> > May I suggest another simple approach? The first continuous couples of
> > sections are always safely section-mapped inside alloc_init_section
> funtion.
> > So, by limiting memblock_alloc to the end of the first continuous
> > couples of sections at the start of map_lowmem, map_lowmem can safely
> > memblock_alloc & memset even if we have one or more section-unaligned
> > memory regions. The limit can be extended back to arm_lowmem_limit after
> the map_lowmem is done.
>
> No. What if the first block of memory is not large enough to handle all
the
> allocations?
>
Thank you for your comment, Russell. I sent a modified patch not to limit to
the first memory memblock_region as a reply to Dave's message.

> I think the real problem is folk trying to reserve small amounts. I have
> said all reservations must be aligned to 1MB.
>
Ok, now I know your thought about arm_memblock_steal(). Then, how about
adding a simple aligning to prevent the possible problem just like me:

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index f54d592..d0daf0d 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -324,6 +324,8 @@ phys_addr_t __init arm_memblock_steal(phys_addr_t size,
phys

BUG_ON(!arm_memblock_steal_permitted);

+ size = ALIGN(size, SECTION_SIZE);
+
phys = memblock_alloc(size, align);
memblock_free(phys, size);
memblock_remove(phys, size);

or, leaving a few comments about the restriction kindly..?