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SubjectRe: [PATCH 00/14] MIPS: memblock: Switch arch code to NO_BOOTMEM
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Hi Serge,

On 17/01/18 22:22, Serge Semin wrote:
> Even though it's common to see the architecture code using both
> bootmem and memblock early memory allocators, it's not good for
> multiple reasons. First of all, it's redundant to have two
> early memory allocator while one would be more than enough from
> functionality and stability points of view. Secondly, some new
> features introduced in the kernel utilize the methods of the most
> modern allocator ignoring the older one. It means the architecture
> code must keep the both subsystems up synchronized with information
> about memory regions and reservations, which leads to the code
> complexity increase, that obviously increases bugs probability.
> Finally it's better to keep all the architectures code unified for
> better readability and code simplification. All these reasons lead
> to one conclusion - arch code should use just one memory allocator,
> which is supposed to be memblock as the most modern and already
> utilized by the most of the kernel platforms. This patchset is
> mostly about it.
>
> One more reason why the MIPS arch code should finally move to
> memblock is a BUG somewhere in the initialization process, when
> CMA is activated:
>
> [ 0.248762] BUG: Bad page state in process swapper/0 pfn:01f93
> [ 0.255415] page:8205b0ac count:0 mapcount:-127 mapping: (null) index:0x1
> [ 0.263172] flags: 0x40000000()
> [ 0.266723] page dumped because: nonzero mapcount
> [ 0.272049] Modules linked in:
> [ 0.275511] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.88-module #5
> [ 0.282900] Stack : 00000000 00000000 80b6dd6a 0000003a 00000000 00000000 80930000 8092bff4
> 86073a14 80ac88c7 809f21ac 00000000 00000001 80b6998c 00000400 00000000
> 80a00000 801822e8 80b6dd68 00000000 00000002 00000000 809f8024 86077ccc
> 80b80000 801e9328 809fcbc0 00000000 00000400 00010000 86077ccc 86073a14
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> ...
> [ 0.323148] Call Trace:
> [ 0.325935] [<8010e7c4>] show_stack+0x8c/0xa8
> [ 0.330859] [<80404814>] dump_stack+0xd4/0x110
> [ 0.335879] [<801f0bc0>] bad_page+0xfc/0x14c
> [ 0.340710] [<801f0e04>] free_pages_prepare+0x1f4/0x330
> [ 0.346632] [<801f36c4>] __free_pages_ok+0x2c/0x104
> [ 0.352154] [<80b23a40>] init_cma_reserved_pageblock+0x5c/0x74
> [ 0.358761] [<80b29390>] cma_init_reserved_areas+0x1b4/0x240
> [ 0.365170] [<8010058c>] do_one_initcall+0xe8/0x27c
> [ 0.370697] [<80b14e60>] kernel_init_freeable+0x200/0x2c4
> [ 0.376828] [<808faca4>] kernel_init+0x14/0x104
> [ 0.381939] [<80107598>] ret_from_kernel_thread+0x14/0x1c
>
> The bugus pfn seems to be the one allocated for bootmem allocator
> pages and hasn't been freed before letting the CMA working with its
> areas. Anyway the bug is solved by this patchset.
>
> Another reason why this patchset is useful is that it fixes the fdt
> reserved-memory nodes functionality for MIPS. Really it's bug to have
> the fdt reserved nodes scanning before the memblock is
> fully initialized (calling early_init_fdt_scan_reserved_mem before
> bootmem_init is called). Additionally no-map flag of the
> reserved-memory node hasn't been taking into account. This patchset
> fixes all of these.
>
> As you probably remember I already did another attempt to merge a
> similar functionality into the kernel. This time the patchset got
> to be less complex (14 patches vs 21 last time) and fixes the
> platform code like SGI IP27 and Loongson3, which due to being
> NUMA introduce its own memory initialization process. Although
> I have much doubt in SGI IP27 code operability in the first place,
> since it got prom_meminit() method of early memory initialization,
> which hasn't been called at any other place in the kernel. It must
> have been left there unrenamed after arch/mips/mips-boards/generic
> code had been discarded.
>
> Here are the list of folks, who agreed to perform some tests of
> the patchset:
> Alexander Sverdlin <alexander.sverdlin@nokia.com> - Octeon2
> Matt Redfearn <matt.redfearn@mips.com> - Loongson3, etc


I have applied and tested these patches on various platforms that we
have available here, and the kernel appears to boot and get to userspace
as normal on the following platforms:

UTM8 (Cavium Octeon III)
Creator CI20
Creator CI40
Loongson3a
MIPS Boston
MIPS Malta
MIPS SEAD3

Aside from the CONFIG_RELOCATABLE stuff, this looks pretty tidy to me.

Thanks,
Matt


> Joshua Kinard <kumba@gentoo.org> - IP27
> Marcin Nowakowski <marcin.nowakowski@mips.com>
> Thanks to you all in regards and for everybody, who will be involved
> in reviewing and testing.
>
> The patchset is applied on top of kernel 4.15-rc8 and can be found
> submitted at my repo:
> https://github.com/fancer/Linux-kernel-MIPS-memblock-project
>
> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
>
> Serge Semin (14):
> MIPS: memblock: Add RESERVED_NOMAP memory flag
> MIPS: memblock: Surely map BSS kernel memory section
> MIPS: memblock: Reserve initrd memory in memblock
> MIPS: memblock: Discard bootmem initialization
> MIPS: memblock: Add reserved memory regions to memblock
> MIPS: memblock: Reserve kdump/crash regions in memblock
> MIPS: memblock: Mark present sparsemem sections
> MIPS: memblock: Simplify DMA contiguous reservation
> MIPS: memblock: Allow memblock regions resize
> MIPS: memblock: Perform early low memory test
> MIPS: memblock: Print out kernel virtual mem layout
> MIPS: memblock: Discard bootmem from Loongson3 code
> MIPS: memblock: Discard bootmem from SGI IP27 code
> MIPS: memblock: Deactivate bootmem allocator
>
> arch/mips/Kconfig | 2 +-
> arch/mips/include/asm/bootinfo.h | 1 +
> arch/mips/kernel/prom.c | 8 +-
> arch/mips/kernel/setup.c | 218 +++++++++------------
> arch/mips/loongson64/loongson-3/numa.c | 16 +-
> arch/mips/mm/init.c | 47 +++++
> arch/mips/sgi-ip27/ip27-memory.c | 9 +-
> 7 files changed, 153 insertions(+), 148 deletions(-)
>

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