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From: david.abdurachmanov@gmail.com (David Abdurachmanov)
To: linux-riscv@lists.infradead.org
Subject: [PATCH] riscv: add S and U modes to ISA string
Date: Mon, 12 Nov 2018 07:29:13 +0100	[thread overview]
Message-ID: <CAEn-LTqd3+t+zhmbbZ3CjPMnFOsUxy0pVNUkgvU5T7yQU_DkcQ@mail.gmail.com> (raw)
In-Reply-To: <mhng-58f419dd-47a6-4540-91b6-08be173d4216@palmer-si-x1c4>

On Sun, Nov 11, 2018 at 11:14 PM Palmer Dabbelt <palmer@sifive.com> wrote:
>
> On Sat, 10 Nov 2018 00:35:15 PST (-0800), me at packi.ch wrote:
> > On 10.11.18 07:45, David Abdurachmanov wrote:
> >>
> >> The patch adds the missing S and U modes.
> >
> > This is the same patch I submitted earlier (see v2 here [1], based on
> > Palmer's feedback). Palmer stated that the "S" extension should not be
> > exposed to usermode.
> >
> > Since two people arrived at the same solution, I wonder if the
> > supervisor mode should really be hidden from userspace, as it's about
> > the CPU information, not about the environment the calling code is
> > running as.
> >
> > [1] https://lkml.org/lkml/2018/11/10/96
>
> I still think S should be hidden from applications.  This patch was fairly
> mechanical, so it probably just wasn't though about twice -- that's the problem
> with user ABI stuff, lots of times the obvious answer isn't the correct one :).
>
True. It was mechanical based on warnings I noticed while booting Fedora
with latest kernel and BBL.

Also true, that /proc/cpuinfo doesn't need to reveal all things to user space
(especially if you don't want various programs to depend on it as some
tend to parse /proc/cpuinfo).

Note, that on server systems which probably would implement SMBIOS
(based on the current proposal for RISC-V) the administrator could
check for S mode.

WARNING: multiple messages have this Message-ID (diff)
From: David Abdurachmanov <david.abdurachmanov@gmail.com>
To: Palmer Dabbelt <palmer@sifive.com>
Cc: me@packi.ch, aou@eecs.berkeley.edu,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: add S and U modes to ISA string
Date: Mon, 12 Nov 2018 07:29:13 +0100	[thread overview]
Message-ID: <CAEn-LTqd3+t+zhmbbZ3CjPMnFOsUxy0pVNUkgvU5T7yQU_DkcQ@mail.gmail.com> (raw)
Message-ID: <20181112062913.ReFy2CG8W60fCUNYtHJKfjMaUuI_jvVfY9Ugxr1Yr3U@z> (raw)
In-Reply-To: <mhng-58f419dd-47a6-4540-91b6-08be173d4216@palmer-si-x1c4>

On Sun, Nov 11, 2018 at 11:14 PM Palmer Dabbelt <palmer@sifive.com> wrote:
>
> On Sat, 10 Nov 2018 00:35:15 PST (-0800), me@packi.ch wrote:
> > On 10.11.18 07:45, David Abdurachmanov wrote:
> >>
> >> The patch adds the missing S and U modes.
> >
> > This is the same patch I submitted earlier (see v2 here [1], based on
> > Palmer's feedback). Palmer stated that the "S" extension should not be
> > exposed to usermode.
> >
> > Since two people arrived at the same solution, I wonder if the
> > supervisor mode should really be hidden from userspace, as it's about
> > the CPU information, not about the environment the calling code is
> > running as.
> >
> > [1] https://lkml.org/lkml/2018/11/10/96
>
> I still think S should be hidden from applications.  This patch was fairly
> mechanical, so it probably just wasn't though about twice -- that's the problem
> with user ABI stuff, lots of times the obvious answer isn't the correct one :).
>
True. It was mechanical based on warnings I noticed while booting Fedora
with latest kernel and BBL.

Also true, that /proc/cpuinfo doesn't need to reveal all things to user space
(especially if you don't want various programs to depend on it as some
tend to parse /proc/cpuinfo).

Note, that on server systems which probably would implement SMBIOS
(based on the current proposal for RISC-V) the administrator could
check for S mode.

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  parent reply	other threads:[~2018-11-12  6:29 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-10  6:45 [PATCH] riscv: add S and U modes to ISA string David Abdurachmanov
2018-11-10  6:45 ` David Abdurachmanov
2018-11-10  8:35 ` Patrick Staehlin
2018-11-10  8:35   ` Patrick Staehlin
2018-11-11 22:14   ` Palmer Dabbelt
2018-11-11 22:14     ` Palmer Dabbelt
2018-11-12  6:29     ` David Abdurachmanov [this message]
2018-11-12  6:29       ` David Abdurachmanov

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