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Date:   Fri, 12 Feb 2021 12:35:15 +0000
From:   Mark Brown <broonie@kernel.org>
To:     Steven Price <steven.price@arm.com>
Cc:     sonicadvance1@gmail.com, amanieu@gmail.com,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Dave Martin <Dave.Martin@arm.com>,
        Amit Daniel Kachhap <amit.kachhap@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        David Brazdil <dbrazdil@google.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Gavin Shan <gshan@redhat.com>, Mike Rapoport <rppt@kernel.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Kristina Martsenko <kristina.martsenko@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Kevin Hao <haokexin@gmail.com>,
        Jason Yan <yanaijie@huawei.com>, Andrey Ignatov <rdna@fb.com>,
        Peter Collingbourne <pcc@google.com>,
        Julien Grall <julien.grall@arm.com>,
        Tian Tao <tiantao6@hisilicon.com>,
        Qais Yousef <qais.yousef@arm.com>,
        Jens Axboe <axboe@kernel.dk>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [RESEND RFC PATCH v2] arm64: Exposes support for 32-bit syscalls
Message-ID: <20210212123515.GC6057@sirena.org.uk>
References: <20210211202208.31555-1-Sonicadvance1@gmail.com>
 <58b03e17-3729-99ea-8691-0d735a53b9bc@arm.com>
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On Fri, Feb 12, 2021 at 11:30:41AM +0000, Steven Price wrote:
> On 11/02/2021 20:21, sonicadvance1@gmail.com wrote:

> > Why do we need compatibility layers?
> > There are ARMv8 CPUs that only support AArch64 but still need to run
> > AArch32 applications.
> > Cortex-A34/R82 and other cores are prime examples of this.
> > Additionally if a user is needing to run legacy 32-bit x86 software, it
> > needs the same compatibility layer.

> Unless I'm much mistaken QEMU's user mode already does this - admittedly I
> don't tend to run "legacy 32-bit x86 software".

Yes, this has been deployed on Debian for a long time - you can install
any combination of Debian architectures on a single system and it will
use qemu to run binaries that can't be supported natively by the
hardware.

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