Received-SPF: pass (google.com: domain of linux-kernel+bounces-122621-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Precedence: bulk
MIME-Version: 1.0
References: <20240326101448.3453626-1-ryan.roberts@arm.com>
 <20240327190723.185232-1-ryan.roberts@arm.com> <CAMj1kXF68MH0HUH8FHpHAoSs_tPbMGek5mY2U4BL-i_RWoZ+5Q@mail.gmail.com>
 <a6da59d1-28b5-4cc0-aae9-fca1286be577@arm.com>
In-Reply-To: <a6da59d1-28b5-4cc0-aae9-fca1286be577@arm.com>
From: Ard Biesheuvel <ardb@kernel.org>
Date: Thu, 28 Mar 2024 10:56:21 +0200
Message-ID: <CAMj1kXGY6d64PO9x1TwGv4mpZ8gFdSbkuxHz-S=z8tDPKHENOQ@mail.gmail.com>
Subject: Re: [PATCH v1] arm64: mm: Batch dsb and isb when populating pgtables
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, David Hildenbrand <david@redhat.com>, 
	Donald Dutile <ddutile@redhat.com>, Eric Chanudet <echanude@redhat.com>, 
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

On Thu, 28 Mar 2024 at 10:45, Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> On 28/03/2024 07:23, Ard Biesheuvel wrote:
> > On Wed, 27 Mar 2024 at 21:07, Ryan Roberts <ryan.roberts@arm.com> wrote:
> >>
> >> After removing uneccessary TLBIs, the next bottleneck when creating the
> >> page tables for the linear map is DSB and ISB, which were previously
> >> issued per-pte in __set_pte(). Since we are writing multiple ptes in a
> >> given pte table, we can elide these barriers and insert them once we
> >> have finished writing to the table.
> >>
> >
> > Nice!
> >
> >> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> >> ---
> >>  arch/arm64/include/asm/pgtable.h |  7 ++++++-
> >>  arch/arm64/mm/mmu.c              | 13 ++++++++++++-
> >>  2 files changed, 18 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> >> index bd5d02f3f0a3..81e427b23b3f 100644
> >> --- a/arch/arm64/include/asm/pgtable.h
> >> +++ b/arch/arm64/include/asm/pgtable.h
> >> @@ -271,9 +271,14 @@ static inline pte_t pte_mkdevmap(pte_t pte)
> >>         return set_pte_bit(pte, __pgprot(PTE_DEVMAP | PTE_SPECIAL));
> >>  }
> >>
> >> -static inline void __set_pte(pte_t *ptep, pte_t pte)
> >> +static inline void ___set_pte(pte_t *ptep, pte_t pte)
> >
> > IMHO, we should either use WRITE_ONCE() directly in the caller, or
> > find a better name.
>
> How about __set_pte_nosync() ?
>

Works for me.