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Message-ID: <mhng-30c89107-c103-4363-b4af-7778d9512622@palmer-ri-x1c9>
Date: Wed, 05 Oct 2022 18:05:28 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: jszhang@...nel.org
CC: Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
ryabinin.a.a@...il.com, glider@...gle.com, andreyknvl@...il.com,
dvyukov@...gle.com, vincenzo.frascino@....com,
alexandre.ghiti@...onical.com, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com
Subject: Re: [PATCH v6 RESEND 0/2] use static key to optimize pgtable_l4_enabled
On Sun, 21 Aug 2022 07:09:16 PDT (-0700), jszhang@...nel.org wrote:
> The pgtable_l4|[l5]_enabled check sits at hot code path, performance
> is impacted a lot. Since pgtable_l4|[l5]_enabled isn't changed after
> boot, so static key can be used to solve the performance issue[1].
>
> An unified way static key was introduced in [2], but it only targets
> riscv isa extension. We dunno whether SV48 and SV57 will be considered
> as isa extension, so the unified solution isn't used for
> pgtable_l4[l5]_enabled now.
>
> patch1 fixes a NULL pointer deference if static key is used a bit earlier.
> patch2 uses the static key to optimize pgtable_l4|[l5]_enabled.
>
> [1] http://lists.infradead.org/pipermail/linux-riscv/2021-December/011164.html
> [2] https://lore.kernel.org/linux-riscv/20220517184453.3558-1-jszhang@kernel.org/T/#t
>
> Since v5:
> - Use DECLARE_STATIC_KEY_FALSE
>
> Since v4:
> - rebased on v5.19-rcN
> - collect Reviewed-by tags
> - Fix kernel panic issue if SPARSEMEM is enabled by moving the
> riscv_finalise_pgtable_lx() after sparse_init()
>
> Since v3:
> - fix W=1 call to undeclared function 'static_branch_likely' error
>
> Since v2:
> - move the W=1 warning fix to a separate patch
> - move the unified way to use static key to a new patch series.
>
> Since v1:
> - Add a W=1 warning fix
> - Fix W=1 error
> - Based on v5.18-rcN, since SV57 support is added, so convert
> pgtable_l5_enabled as well.
>
>
> Jisheng Zhang (2):
> riscv: move sbi_init() earlier before jump_label_init()
> riscv: turn pgtable_l4|[l5]_enabled to static key for RV64
>
> arch/riscv/include/asm/pgalloc.h | 16 ++++----
> arch/riscv/include/asm/pgtable-32.h | 3 ++
> arch/riscv/include/asm/pgtable-64.h | 60 ++++++++++++++++++---------
> arch/riscv/include/asm/pgtable.h | 5 +--
> arch/riscv/kernel/cpu.c | 4 +-
> arch/riscv/kernel/setup.c | 2 +-
> arch/riscv/mm/init.c | 64 ++++++++++++++++++-----------
> arch/riscv/mm/kasan_init.c | 16 ++++----
> 8 files changed, 104 insertions(+), 66 deletions(-)
Sorry for being slow here, but it looks like this still causes some
early boot hangs. Specifically kasan+sparsemem is failing. As you can
probably see from the latency I'm still a bit buried right now so I'm
not sure when I'll have a chance to take more of a look.
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