Re: [PATCH] riscv: deprecate CONFIG_MMU=n

From: Charles Lohr <lohr85@gmail.com>
To: Conor Dooley <conor@kernel.org>
Cc: "Clément Léger" <cleger@rivosinc.com>,
	"Samuel Holland" <samuel.holland@sifive.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Conor Dooley" <conor.dooley@microchip.com>,
	"Andrew Jones" <ajones@ventanamicro.com>,
	"Damien Le Moal" <dlemoal@kernel.org>,
	"Björn Töpel" <bjorn@rivosinc.com>,
	"Atish Patra" <atishp@rivosinc.com>
Subject: Re: [PATCH] riscv: deprecate CONFIG_MMU=n
Date: Mon, 26 Feb 2024 11:00:41 -0800	[thread overview]
Message-ID: <CAGu26P_v9FjYq9Bncvfd-dBhdHQevvN3HpO1nqjA2hYFCpG7hg@mail.gmail.com> (raw)
In-Reply-To: <20240226-pajamas-okay-51e16426b0f5@spud>

WOAH! Please DO NOT deprecate NOMMU. I use the NOMMU build constantly
and NOMMU Linux on RISC-V is the avenue used by many FPGA soft cores
for Linux, as well as some limited systems.

I get new copies of the kernel when there are releases and test them
frequently to make sure everything is still working as expected.

For us we just don't care about XIP. I mean if someone did push it
through to fruition, I'd also test and use it, but I urge you please
do not deprecate this.  While it's sometimes needed a bit of a
creative build to get everything working, I've never needed to patch
anything in the kernel beyond patching in a custom console for serial
output.

I am happy to discuss the possibility of me and or one of the other
RISC-V soft (FPGA) core people stepping up to try to be more active,
but so far we've just been very well serviced by the current NOMMU
Linux setup.

Charles

On Mon, Feb 26, 2024 at 8:03 AM Conor Dooley <conor@kernel.org> wrote:
>
> On Mon, Feb 26, 2024 at 04:25:24PM +0100, Clément Léger wrote:
> > I guess I could also mark XIP as deprecated.
>
> I'm not so sure, people recently added XIP support to QEMU (and sent
> kernel fixes in December). XIP is also not nearly as much of a problem
> to support, there's far less that it does differently, the main barrier
> was the inability to test it which is no longer the case.
> That said, XIP is gonna kill itself off I feel as it does not support
> runtime patching and therefore is extremely limited on extensions, given
> we use alternatives for all of that (although I suppose if someone has a
> usecase they could make nasty macros worse and implement a compiletime
> switch in the alternatives too).
>
> Cheers,
> Conor.
>
> _______________________________________________
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> linux-riscv@lists.infradead.org
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