From: Daniel Axtens <dja@axtens.net>
To: Lukas Bulwahn <lukas.bulwahn@gmail.com>,
Paul Mackerras <paulus@ozlabs.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Neuling <mikey@neuling.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>,
kernel-janitors@vger.kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] powerpc: rectify selection to ARCH_ENABLE_SPLIT_PMD_PTLOCK
Date: Fri, 20 Aug 2021 10:03:08 +1000 [thread overview]
Message-ID: <87pmu99e4j.fsf@dja-thinkpad.axtens.net> (raw)
In-Reply-To: <20210819113954.17515-3-lukas.bulwahn@gmail.com>
Lukas Bulwahn <lukas.bulwahn@gmail.com> writes:
> Commit 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK")
> selects the non-existing config ARCH_ENABLE_PMD_SPLIT_PTLOCK in
> ./arch/powerpc/platforms/Kconfig.cputype, but clearly it intends to select
> ARCH_ENABLE_SPLIT_PMD_PTLOCK here (notice the word swapping!), as this
> commit does select that for all other architectures.
>
> Rectify selection to ARCH_ENABLE_SPLIT_PMD_PTLOCK instead.
>
Yikes, yes, 66f24fa766e3 does seem to have got that wrong. It looks like
that went into 5.13.
I think we want to specifically target this for stable so that we don't
lose the perfomance and scalability benefits of split pmd ptlocks:
Cc: stable@vger.kernel.org # v5.13+
(I don't think you need to do another revision for this, I think mpe
could add it when merging.)
I tried to check whether we accidentally broke SPLIT_PMD_PTLOCKs while
they were disabled:
- There hasn't been any change to the pgtable_pmd_page_ctor or _dtor
prototypes, and we haven't made any relevant changes to any of the
files in arch/powerpc that called it.
- I checked out v5.13 and powerpc/merge, applied this patch, built a
pseries_le_defconfig and boot tested it in qemu. It didn't crash on
boot or with /bin/sh and some shell commands, but I didn't exactly
stress test the VM subsystem either.
This gives me some confidence it's both good for powerpc and stable-worthy.
Overall:
Reviewed-by: Daniel Axtens <dja@axtens.net>
Kind regards,
Daniel
> Fixes: 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK")
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
> ---
> arch/powerpc/platforms/Kconfig.cputype | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
> index 6794145603de..a208997ade88 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -98,7 +98,7 @@ config PPC_BOOK3S_64
> select PPC_HAVE_PMU_SUPPORT
> select HAVE_ARCH_TRANSPARENT_HUGEPAGE
> select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
> - select ARCH_ENABLE_PMD_SPLIT_PTLOCK
> + select ARCH_ENABLE_SPLIT_PMD_PTLOCK
> select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
> select ARCH_SUPPORTS_HUGETLBFS
> select ARCH_SUPPORTS_NUMA_BALANCING
> --
> 2.26.2
next prev parent reply other threads:[~2021-08-20 0:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-19 11:39 [PATCH v2 0/2] Kconfig symbol fixes on powerpc Lukas Bulwahn
2021-08-19 11:39 ` [PATCH v2 1/2] powerpc: kvm: remove obsolete and unneeded select Lukas Bulwahn
2021-08-19 22:39 ` Daniel Axtens
2021-08-19 11:39 ` [PATCH v2 2/2] powerpc: rectify selection to ARCH_ENABLE_SPLIT_PMD_PTLOCK Lukas Bulwahn
2021-08-20 0:03 ` Daniel Axtens [this message]
2021-08-20 4:25 ` Michael Ellerman
2021-08-19 11:50 ` [PATCH v2 0/2] Kconfig symbol fixes on powerpc Christophe Leroy
2021-08-27 13:15 ` Michael Ellerman
2021-08-27 13:28 ` Michael Ellerman
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