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From: Christoph Hellwig <hch@infradead.org>
To: Paul Walmsley <paul.walmsley@sifive.com>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	Alexandre Ghiti <alex@ghiti.fr>
Subject: Re: [PATCH] riscv: kbuild: add virtual memory system selection
Date: Fri, 2 Aug 2019 01:44:53 -0700	[thread overview]
Message-ID: <20190802084453.GA1410@infradead.org> (raw)
In-Reply-To: <alpine.DEB.2.21.9999.1907261259420.26670@viisi.sifive.com>

On Fri, Jul 26, 2019 at 01:00:49PM -0700, Paul Walmsley wrote:
> 
> The RISC-V specifications currently define three virtual memory
> translation systems: Sv32, Sv39, and Sv48.  Sv32 is currently specific
> to 32-bit systems; Sv39 and Sv48 are currently specific to 64-bit
> systems.  The current kernel only supports Sv32 and Sv39, but we'd
> like to start preparing for Sv48.  As an initial step, allow the
> virtual memory translation system to be selected via kbuild, and stop
> the build if an option is selected that the kernel doen't currently
> support.
> 
> This patch currently has no functional impact.

It cause the user to be able to select a config which thus won't build.
So it is not just useless, which already is a reason not to merge it,
but actively harmful, which is even worse.

Even if we assume we want to implement Sv48 eventually (which seems
to be a bit off), we need to make this a runtime choice and not a
compile time one to not balloon the number of configs that distributions
(and kernel developers) need to support.

  parent reply	other threads:[~2019-08-02  8:44 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-26 20:00 Paul Walmsley
2019-07-28 13:38 ` Bin Meng
2019-07-31 19:37   ` Paul Walmsley
2019-08-01  8:56     ` Bin Meng
2019-08-02  8:44 ` Christoph Hellwig [this message]
2019-08-07  0:02   ` Paul Walmsley
2019-08-07  5:42     ` Christoph Hellwig
2019-08-07  7:04       ` Alexandre Ghiti
2019-08-07 15:12         ` Christoph Hellwig
2019-08-07 16:20           ` Palmer Dabbelt
2019-08-07 16:42         ` Paul Walmsley

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