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

From: Dennis Zhou <dennis@kernel.org>
To: Tejun Heo <tj@kernel.org>, Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Alexander Potapenko <glider@google.com>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Arnd Bergmann <arnd@arndb.de>, Christoph Lameter <cl@linux.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	kasan-dev@googlegroups.com, linux-arch@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 0/2] riscv: Enable percpu page first chunk allocator
Date: Wed, 6 Dec 2023 21:46:48 -0800	[thread overview]
Message-ID: <ZXFcSEzalzl790bO@snowbird> (raw)
In-Reply-To: <ZXDEyzVcBOPUCCpg@slm.duckdns.org>

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

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