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From: Jisheng Zhang <jszhang@kernel.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Conor Dooley <conor.dooley@microchip.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: RISCV_ISA_SV48 and RISCV_ISA_SV57 should depend on MMU
Date: Thu, 15 Oct 2026 19:48:29 +0800	[thread overview]
Message-ID: <atC9jZIF1T1x0w1X@xhacker> (raw)
In-Reply-To: <CAMuHMdWB+Aj7HK3YaHgo8VcypBamN9Yqi-M8WYtKpRu+ZG7yFA@mail.gmail.com>

On Thu, Oct 15, 2026 at 09:43:40AM +0200, Geert Uytterhoeven wrote:
> Hi Jisheng,
> 
> On Thu, 15 Oct 2026 at 01:48, Jisheng Zhang <jszhang@kernel.org> wrote:
> > On Wed, Oct 14, 2026 at 12:20:39PM +0200, Geert Uytterhoeven wrote:
> > > These options are irreleant for nommu systems.
> > >
> > > Fixes: 36de74049ec8cb1a ("riscv: introduce RISCV_ISA_SV48 and RISCV_ISA_SV57")
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> 
> > > --- a/arch/riscv/Kconfig
> > > +++ b/arch/riscv/Kconfig
> > > @@ -605,7 +605,7 @@ config RISCV_ISA_SSQOSID
> > >
> > >  config RISCV_ISA_SV48
> > >       bool "Page-Based 48-bit Virtual-Memory System"
> > > -     depends on 64BIT
> > > +     depends on 64BIT && MMU
> > >       default y
> > >       help
> > >         Add support for the Page-Based 48-bit Virtual-Memory System.
> > > @@ -617,7 +617,7 @@ config RISCV_ISA_SV48
> > >
> > >  config RISCV_ISA_SV57
> > >       bool "Page-Based 57-bit Virtual-Memory System"
> > > -     depends on 64BIT
> > > +     depends on 64BIT && MMU
> >
> > hmm, I think we also need to make RISCV_ISA_SV57 depend on
> > RISCV_ISA_SV48. Otherwise, there's a case: RISCV_ISA_SV57 &&
> > !RISCV_ISA_SV48. Human won't make this wrong combination, but
> > the random config can.
> 
> Is that really an issue?
> If I build a kernel for an SV57-system, do I really need to enable
> support for SV48, too? It builds fine without...

This is to align with the spec:
"implementations that support Sv57 must also support Sv48"


> 
> > with that change,
> > Reviewed-by: Jisheng Zhang <jszhang@kernel.org>
> 
> Thanks!
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

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  reply	other threads:[~2026-10-15 12:08 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-14 10:20 [PATCH] riscv: RISCV_ISA_SV48 and RISCV_ISA_SV57 should depend on MMU Geert Uytterhoeven
2026-10-14 23:28 ` Jisheng Zhang
2026-10-15  7:43   ` Geert Uytterhoeven
2026-10-15 11:48     ` Jisheng Zhang [this message]
2026-10-15 12:24       ` Geert Uytterhoeven

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