lkml.org 
[lkml]   [2014]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] arm64: fix MAX_ORDER for 64K pagesize
On Wed, 11 Jun 2014, Mark Salter wrote:

> With a kernel configured with ARM64_64K_PAGES && !TRANSPARENT_HUGEPAGE
> I get this at early boot:
>
> SMP: Total of 8 processors activated.
> devtmpfs: initialized
> Unable to handle kernel NULL pointer dereference at virtual address 00000008
> pgd = fffffe0000050000
> [00000008] *pgd=00000043fba00003, *pmd=00000043fba00003, *pte=00e0000078010407
> Internal error: Oops: 96000006 [#1] SMP
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.15.0-rc864k+ #44
> task: fffffe03bc040000 ti: fffffe03bc080000 task.ti: fffffe03bc080000
> PC is at __list_add+0x10/0xd4
> LR is at free_one_page+0x270/0x638
> ...
> Call trace:
> [<fffffe00003ee970>] __list_add+0x10/0xd4
> [<fffffe000019c478>] free_one_page+0x26c/0x638
> [<fffffe000019c8c8>] __free_pages_ok.part.52+0x84/0xbc
> [<fffffe000019d5e8>] __free_pages+0x74/0xbc
> [<fffffe0000c01350>] init_cma_reserved_pageblock+0xe8/0x104
> [<fffffe0000c24de0>] cma_init_reserved_areas+0x190/0x1e4
> [<fffffe0000090418>] do_one_initcall+0xc4/0x154
> [<fffffe0000bf0a50>] kernel_init_freeable+0x204/0x2a8
> [<fffffe00007520a0>] kernel_init+0xc/0xd4
>
> This happens in this configuration because __free_one_page() is called
> with an order greater than MAX_ORDER, accesses past zone->free_list[]
> and passes a bogus list_head to list_add().
>
> arch/arm64/Kconfig has:
>
> config FORCE_MAX_ZONEORDER
> int
> default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)
> default "11"
>
> So with THP turned off MAX_ORDER == 11 but init_cma_reserved_pageblock()
> passes __free_pages() an order of pageblock_order which is based on
> (HPAGE_SHIFT - PAGE_SHIFT) which is 13 for 64K pages. I worked around
> this by removing the THP test so FORCE_MAX_ZONEORDER is always 14 for
> ARM64_64K_PAGES.
>
> Signed-off-by: Mark Salter <msalter@redhat.com>
> ---
> arch/arm64/Kconfig | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 7295419..42a334e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -269,7 +269,7 @@ config XEN
>
> config FORCE_MAX_ZONEORDER
> int
> - default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)
> + default "14" if ARM64_64K_PAGES
> default "11"
>
> endmenu

Any reason to not switch this to

ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE && CMA

instead? If pageblock_order > MAX_ORDER because of
HPAGE_SHIFT > PAGE_SHIFT, then cma is always going to be passing a
too-large-order to free_pages_prepare() via this path.

Adding Michal and Marek to the cc.


\
 
 \ /
  Last update: 2014-06-12 01:21    [W:0.105 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site