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Sat, 5 Aug 2023 22:41:25 +1000 (AEST) From: Michael Ellerman To: Christophe Leroy , "linuxppc-dev@lists.ozlabs.org" Cc: "rppt@kernel.org" , "akpm@linux-foundation.org" , "linux-mm@kvack.org" Subject: Re: [PATCH] powerpc/mm: Reinstate ARCH_FORCE_MAX_ORDER ranges In-Reply-To: <8011d806-5b30-bf26-2bfe-a08c39d57e20@csgroup.eu> References: <20230519113806.370635-1-mpe@ellerman.id.au> <8011d806-5b30-bf26-2bfe-a08c39d57e20@csgroup.eu> Date: Sat, 05 Aug 2023 22:41:24 +1000 Message-ID: <87v8dt4q6j.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 4o35by6g57e8t939w86xoqek33cxiqau X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 1A4D520023 X-Rspam-User: X-HE-Tag: 1691239290-556589 X-HE-Meta: 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 vLZhX+UD oPzHN9ZplM7Q71jpzWr5MXeVcl4/+5V6YAX+xYK8eedEtaKUO8p/QB8qdVd8Bc5zG03s0Cm0XWMCVYP3zW/opPwgwAC6k4MkOQ6eYSbzpuxdmQf2dQxoDWp5q4q/orBlw54/DobD6KP2IE2lsLCO20voNQj4TGOS7rIMWfTtbGjHArOefA0Kmh6vGUAbcYKKfAtMU/+cq3b3Z4qTKpUby76uU/E6cIGlGxITnagbcN7GukZvxk0Do91xtLKCRoY1uFAeXqiewFepxzXE5mZ4C0UZeyg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Christophe Leroy writes: > Le 19/05/2023 =C3=A0 13:38, Michael Ellerman a =C3=A9crit=C2=A0: >> Commit 1e8fed873e74 ("powerpc: drop ranges for definition of >> ARCH_FORCE_MAX_ORDER") removed the limits on the possible values for >> ARCH_FORCE_MAX_ORDER. >> >> However removing the ranges entirely causes some common work flows to >> break. For example building a defconfig (which uses 64K pages), changing >> the page size to 4K, and rebuilding used to work, because >> ARCH_FORCE_MAX_ORDER would be clamped to 12 by the ranges. >> >> With the ranges removed it creates a kernel that builds but crashes at >> boot: >> kernel BUG at mm/huge_memory.c:470! >> Oops: Exception in kernel mode, sig: 5 [#1] >> ... >> NIP hugepage_init+0x9c/0x278 >> LR do_one_initcall+0x80/0x320 >> Call Trace: >> do_one_initcall+0x80/0x320 >> kernel_init_freeable+0x304/0x3ac >> kernel_init+0x30/0x1a0 >> ret_from_kernel_user_thread+0x14/0x1c >> >> The reasoning for removing the ranges was that some of the values were >> too large. So take that into account and limit the maximums to 10 which >> is the default max, except for the 4K case which uses 12. > > There is something wrong: > > ~# echo 1 > /sys/kernel/mm/hugepages/hugepages-8192kB/nr_hugepages > sh: write error: Invalid argument > > $ grep -e MAX_ORDER -e K_PAGES .config > CONFIG_PPC_4K_PAGES=3Dy > # CONFIG_PPC_16K_PAGES is not set > CONFIG_ARCH_FORCE_MAX_ORDER=3D10 That's 32-bit I guess? So you're hitting the default case, ie. range 10 10. I see we have: arch/powerpc/configs/fsl-emb-nonhw.config:CONFIG_ARCH_FORCE_MAX_ORDER=3D12 And that config fragment is included by: mpc85xx_defconfig mpc85xx_smp_defconfig corenet32_smp_defconfig corenet64_smp_defconfig mpc86xx_defconfig mpc86xx_smp_defconfig So for a lot of platforms the "default" was actually 12 in the past, despite what it says in Kconfig. > In the past MAX_ORDER used to be 12 but now it is force to 10. This should fix it? cheers diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 0b1172cbeccb..b3fdb3d26836 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -917,7 +917,7 @@ config ARCH_FORCE_MAX_ORDER default "6" if PPC32 && PPC_64K_PAGES range 4 10 if PPC32 && PPC_256K_PAGES default "4" if PPC32 && PPC_256K_PAGES - range 10 10 + range 10 12 default "10" help The kernel page allocator limits the size of maximal physically