linux-kernel - Re: [PATCH 0/2] riscv: Enable percpu page first chunk allocator

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Message-ID: <ZXFcSEzalzl790bO@snowbird>
Date:   Wed, 6 Dec 2023 21:46:48 -0800
From:   Dennis Zhou <dennis@...nel.org>
To:     Tejun Heo <tj@...nel.org>, Alexandre Ghiti <alex@...ti.fr>
Cc:     Alexandre Ghiti <alexghiti@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-arch@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 0/2] riscv: Enable percpu page first chunk allocator

Hello,

On Wed, Dec 06, 2023 at 09:00:27AM -1000, Tejun Heo wrote:
> On Wed, Dec 06, 2023 at 11:08:20AM +0100, Alexandre Ghiti wrote:
> > Hi Tejun,
> > 
> > On 10/11/2023 15:07, Alexandre Ghiti wrote:
> > > While working with pcpu variables, I noticed that riscv did not support
> > > first chunk allocation in the vmalloc area which may be needed as a fallback
> > > in case of a sparse NUMA configuration.
> > > 
> > > patch 1 starts by introducing a new function flush_cache_vmap_early() which
> > > is needed since a new vmalloc mapping is established and directly accessed:
> > > on riscv, this would likely fail in case of a reordered access or if the
> > > uarch caches invalid entries in TLB.
> > > 
> > > patch 2 simply enables the page percpu first chunk allocator in riscv.
> > > 
> > > Alexandre Ghiti (2):
> > >    mm: Introduce flush_cache_vmap_early() and its riscv implementation
> > >    riscv: Enable pcpu page first chunk allocator
> > > 
> > >   arch/riscv/Kconfig                  | 2 ++
> > >   arch/riscv/include/asm/cacheflush.h | 3 ++-
> > >   arch/riscv/include/asm/tlbflush.h   | 2 ++
> > >   arch/riscv/mm/kasan_init.c          | 8 ++++++++
> > >   arch/riscv/mm/tlbflush.c            | 5 +++++
> > >   include/asm-generic/cacheflush.h    | 6 ++++++
> > >   mm/percpu.c                         | 8 +-------
> > >   7 files changed, 26 insertions(+), 8 deletions(-)
> > > 
> > 
> > Any feedback regarding this?
> 
> On cursory look, it looked fine to me but Dennis is maintaining the percpu
> tree now. Dennis?
> 

Ah I wasn't sure at the time if we needed this to go through percpu vs
risc v. I need to poke tglx and potentially pull some more stuff so I
can take it.

I regrettably got both the covid and flu vaccines today and feel like a
truck hit me. I'll review this tomorrow and make sure it's taken care
of for the next merge window.

Thanks,
Dennis

> Thanks.
> 
> -- 
> tejun