linux-kernel - Re: [PATCH v15 03/11] riscv/Kconfig: make direct map manipulation options depend on MMU

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Message-ID: <20210123110041.GE6332@kernel.org>
Date:   Sat, 23 Jan 2021 13:00:41 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        luto@...nel.org, Arnd Bergmann <arnd@...db.de>, bp@...en8.de,
        catalin.marinas@....com, cl@...ux.com, dan.j.williams@...el.com,
        dave.hansen@...ux.intel.com, david@...hat.com,
        elena.reshetova@...el.com, hpa@...or.com, mingo@...hat.com,
        jejb@...ux.ibm.com, kirill@...temov.name, willy@...radead.org,
        mark.rutland@....com, rppt@...ux.ibm.com, mtk.manpages@...il.com,
        Paul Walmsley <paul.walmsley@...ive.com>, peterz@...radead.org,
        rick.p.edgecombe@...el.com, guro@...com, shakeelb@...gle.com,
        shuah@...nel.org, tglx@...utronix.de, tycho@...ho.ws,
        will@...nel.org, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org, lkp@...el.com
Subject: Re: [PATCH v15 03/11] riscv/Kconfig: make direct map manipulation
 options depend on MMU

On Fri, Jan 22, 2021 at 08:12:30PM -0800, Palmer Dabbelt wrote:
> On Wed, 20 Jan 2021 10:06:04 PST (-0800), rppt@...nel.org wrote:
> > From: Mike Rapoport <rppt@...ux.ibm.com>
> > 
> > ARCH_HAS_SET_DIRECT_MAP and ARCH_HAS_SET_MEMORY configuration options have
> > no meaning when CONFIG_MMU is disabled and there is no point to enable them
> > for the nommu case.
> > 
> > Add an explicit dependency on MMU for these options.
> > 
> > Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> > Reported-by: kernel test robot <lkp@...el.com>
> > ---
> >  arch/riscv/Kconfig | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index d82303dcc6b6..d35ce19ab1fa 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -25,8 +25,8 @@ config RISCV
> >  	select ARCH_HAS_KCOV
> >  	select ARCH_HAS_MMIOWB
> >  	select ARCH_HAS_PTE_SPECIAL
> > -	select ARCH_HAS_SET_DIRECT_MAP
> > -	select ARCH_HAS_SET_MEMORY
> > +	select ARCH_HAS_SET_DIRECT_MAP if MMU
> > +	select ARCH_HAS_SET_MEMORY if MMU
> >  	select ARCH_HAS_STRICT_KERNEL_RWX if MMU
> >  	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
> >  	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> 
> Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> 
> LMK if you want this to go in via the RISC-V tree, otherwise I'm going to
> assume it's going in along with the rest of these.  FWIW I see these in other
> architectures without the MMU guard.

Except arm, they all always have MMU=y and arm selects only
ARCH_HAS_SET_MEMORY and has empty stubs for those when MMU=n.

Indeed I might have been over zealous adding ARCH_HAS_SET_MEMORY dependency
on MMU, as riscv also has these stubs, but I thought that making this
explicit is a nice thing.
 
> Thanks!

-- 
Sincerely yours,
Mike.