Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 11 Jan 2023 20:00:29 +0100 | From | Andrew Jones <> | Subject | Re: [PATCH v6 RESEND 0/2] use static key to optimize pgtable_l4_enabled |
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On Thu, Jan 12, 2023 at 01:28:40AM +0800, Jisheng Zhang wrote: > On Sun, Dec 11, 2022 at 06:44:04PM +0800, Jisheng Zhang wrote: > > On Sat, Oct 08, 2022 at 10:28:35PM +0800, Jisheng Zhang wrote: > > > On Thu, Oct 06, 2022 at 04:37:57PM +0800, Jisheng Zhang wrote: > > > > On Wed, Oct 05, 2022 at 06:05:28PM -0700, Palmer Dabbelt wrote: > > > > > On Sun, 21 Aug 2022 07:09:16 PDT (-0700), jszhang@kernel.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. > > > > > > > > Hi Palmer, > > > > > > > > Before V4, there is a bug which can cause kernel panic when SPARSEMEM > > > > is enabled, V4 have fixed it by moving the riscv_finalise_pgtable_lx() > > > > after sparse_init(). And I just tested the riscv-pgtable_static_key > > > > branch in your tree, enabling KASAN and SPARSEMEM, system booted fine. > > > > I'm not sure what happened. Could you please send me your kernel > > > > config file? I want to fix any issue which can block this series being > > > > merged in 6.1-rc1. > > > > > > Hi Palmer, > > > > > > I know you are busy ;) Do you have time to send me your test kernel > > > config file so that I can reproduce the "early boot hang"? > > > > > > Thanks > > > > Hi Palmer, > > > > I think the early boot hangs maybe the same as the one which has been > > fixed by commit 9f2ac64d6ca6 ("riscv: mm: add missing memcpy in > > kasan_init"). Will you give this series another try for v6.2-rc1? If > > the boot hang can still be reproduced, could you please send me your > > .config file? > > > > Thanks in advance > Hi all, > > Just request to comment what to do with this patch, I think there > are two independent points to consult: > > 1. IIRC, Palmer gave this patch two chances to merge in early versions > but he found boot hangs if enable KASAN and SPARSEMEM, while I can't > reproduce the boot hang. And I also expect the hang should be fixed by > commit 9f2ac64d6ca6 ("riscv: mm: add missing memcpy in kasan_init") > > 2. Now we know alternative is preferred than static branch for ISA > extensions dynamic code patching. So we also need to switch static > branch usage here to alternative mechanism, but the problem is > SV48 and SV57 are not ISA extensions, so we can't directly make use > of the recently introduced riscv_has_extension_likely|unlikely()[1] > which is based on alternative mechanism.
We could rename the "has_extension" framework to "has_cpufeature" and then lump extensions and features such as sv48 and sv57 together. Or, if it's best to keep extensions separate, then duplicate the framework to create a "has_non_extension_feature" version where features like sv48 and sv57 live.
Thanks, drew
> > Any comments are appreciated. > > Thanks in advance > > [1] https://lore.kernel.org/linux-riscv/20230111171027.2392-1-jszhang@kernel.org/T/#t > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
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