linux-kernel - Re: [PATCH] riscv: export flush_icache

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Message-ID: <alpine.DEB.2.21.9999.1912201500230.57866@viisi.sifive.com>
Date:   Fri, 20 Dec 2019 15:00:41 -0800 (PST)
From:   Paul Walmsley <paul.walmsley@...ive.com>
To:     Olof Johansson <olof@...om.net>
cc:     Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] riscv: export flush_icache_all to modules

On Fri, 20 Dec 2019, Olof Johansson wrote:

> On Fri, Dec 20, 2019 at 3:05 AM Paul Walmsley <paul.walmsley@...ive.com> wrote:
> >
> > On Mon, 16 Dec 2019, Olof Johansson wrote:
> >
> > > This is needed by LKDTM (crash dump test module), it calls
> > > flush_icache_range(), which on RISC-V turns into flush_icache_all(). On
> > > other architectures, the actual implementation is exported, so follow
> > > that precedence and export it here too.
> > >
> > > Fixes build of CONFIG_LKDTM that fails with:
> > > ERROR: "flush_icache_all" [drivers/misc/lkdtm/lkdtm.ko] undefined!
> >
> > In the past we've resisted doing this; see
> >
> > https://lore.kernel.org/linux-riscv/20190611134945.GA28532@lst.de/
> >
> > under the principle that we don't want modules to be able to flush the I$
> > directly via this interface.  But maybe, like moving the L2 related code
> > out of arch/riscv, we should just do it.
> 
> So you are aware that all other architectures that don't have coherent
> icache already exports this, right?
> 
> Being more puritan on RISC-V buys nothing w.r.t. keeping modules from
> doing anything, you'll just end up having to mark a bunch of them
> broken on your architecture. :(

Yep, we'll pick it up.


- Paul