Re: [sw-dev] SBI extension proposal v2

From: "Luís Marques" <luismarques@lowrisc.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "mark.rutland@arm.com" <mark.rutland@arm.com>,
	Christoph Hellwig <hch@infradead.org>,
	Damien Le Moal <Damien.LeMoal@wdc.com>,
	Olof Johansson <olof.johansson@gmail.com>,
	"alankao@andestech.com" <alankao@andestech.com>,
	"abner.chang@hpe.com" <abner.chang@hpe.com>,
	Atish Patra <atish.patra@wdc.com>,
	Anup Patel <anup@brainfault.org>,
	Palmer Dabbelt <palmer@sifive.com>,
	Alexander Graf <agraf@suse.de>,
	"zong@andestech.com" <zong@andestech.com>,
	ron minnich <rminnich@gmail.com>,
	"sw-dev@groups.riscv.org" <sw-dev@groups.riscv.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	"mick@ics.forth.gr" <mick@ics.forth.gr>,
	Alistair Francis <Alistair.Francis@wdc.com>,
	Luke Kenneth Casson Leighton <lkcl@lkcl.net>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	Andrew Waterman <andrew@sifive.com>
Subject: Re: [sw-dev] SBI extension proposal v2
Date: Tue, 5 Feb 2019 23:02:05 +0000	[thread overview]
Message-ID: <CAPhv3nqQRC=jsLuheFPa1=qj7_rZ4D9q8nTr_yK7qeotobPbnA@mail.gmail.com> (raw)
In-Reply-To: <22450f8b5b18421e486985725b1a58167662fd2d.camel@kernel.crashing.org>

On Tue, Feb 5, 2019 at 10:30 PM Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> IMHO, something like SBI has value when seen from the perspective of
> providing a thin abstraction enabling existing OS binaries to run on
> newer/different systems *as a fallback*. This should be done with the
> clear intent and guidance that ultimately, the OS is meant to grow
> native handling for those cases and platforms.

I like the idea of it being a fallback (and thus something that can be
replaced or complemented at runtime by the kernel, or even be absent
when the kernel has full knowledge of the exact hardware details).
That also meshes well with the goal of it being a fairly minimal
abstraction. It's not clear to me that the current design path will
take us there, unless this becomes a well reiterated goal, and the
implementation decision are made in alignment with that goal.

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