[PATCH] riscv: add S and U modes to ISA string

[PATCH] riscv: add S and U modes to ISA string

[David Abdurachmanov]

Booting kernel (4.20-rc1) with riscv-pk @
6ebd0f2a46255d0c76dad3c05b16c1d154795d26 (master/HEAD) on Fedora 29 one gets:

[..]
[   55.075000] unsupported ISA "rv64imafdcsu" in device tree
[   55.075000] unsupported ISA "rv64imafdcsu" in device tree
[   55.076000] unsupported ISA "rv64imafdcsu" in device tree
[   55.076000] unsupported ISA "rv64imafdcsu" in device tree
[   55.077000] systemd[1]: Detected architecture riscv64.
[..]

The patch adds the missing S and U modes.

Signed-off-by: David Abdurachmanov <david.abdurachmanov@gmail.com>
---
 arch/riscv/kernel/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 3a5a2ee31547..4029c7e6872b 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -64,7 +64,7 @@ int riscv_of_processor_hartid(struct device_node *node)
 
 static void print_isa(struct seq_file *f, const char *orig_isa)
 {
-	static const char *ext = "mafdc";
+	static const char *ext = "mafdcsu";
 	const char *isa = orig_isa;
 	const char *e;
 
-- 
2.19.1

[PATCH] riscv: add S and U modes to ISA string

[David Abdurachmanov]

Booting kernel (4.20-rc1) with riscv-pk @
6ebd0f2a46255d0c76dad3c05b16c1d154795d26 (master/HEAD) on Fedora 29 one gets:

[..]
[   55.075000] unsupported ISA "rv64imafdcsu" in device tree
[   55.075000] unsupported ISA "rv64imafdcsu" in device tree
[   55.076000] unsupported ISA "rv64imafdcsu" in device tree
[   55.076000] unsupported ISA "rv64imafdcsu" in device tree
[   55.077000] systemd[1]: Detected architecture riscv64.
[..]

The patch adds the missing S and U modes.

Signed-off-by: David Abdurachmanov <david.abdurachmanov@gmail.com>
---
 arch/riscv/kernel/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 3a5a2ee31547..4029c7e6872b 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -64,7 +64,7 @@ int riscv_of_processor_hartid(struct device_node *node)
 
 static void print_isa(struct seq_file *f, const char *orig_isa)
 {
-	static const char *ext = "mafdc";
+	static const char *ext = "mafdcsu";
 	const char *isa = orig_isa;
 	const char *e;
 
-- 
2.19.1


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[PATCH] riscv: add S and U modes to ISA string

[Patrick Staehlin]

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

Patrick

Re: [PATCH] riscv: add S and U modes to ISA string

[Patrick Staehlin]

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

Patrick

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[PATCH] riscv: add S and U modes to ISA string

[Palmer Dabbelt]

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 :).

I'll take your second patch, I just haven't gotten around to actually fully 
reviewing patches yet as I'm still in my email triage phase.

Thanks!

Re: [PATCH] riscv: add S and U modes to ISA string

[Palmer Dabbelt]

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 :).

I'll take your second patch, I just haven't gotten around to actually fully 
reviewing patches yet as I'm still in my email triage phase.

Thanks!

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[PATCH] riscv: add S and U modes to ISA string

[David Abdurachmanov]

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.

Re: [PATCH] riscv: add S and U modes to ISA string

[David Abdurachmanov]

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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