[PATCH] cpuid.4: note which CPUs don't support CPUID and what happens

[PATCH] cpuid.4: note which CPUs don't support CPUID and what happens

[наб]

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"Early 486" comes from an uncited wikipedia table, added in
  https://en.wikipedia.org/w/index.php?title=CPUID&diff=prev&oldid=592047209
  https://en.wikipedia.org/w/index.php?title=CPUID&diff=prev&oldid=592047978
but I spot-checked the rest of the table accurate to CPUs in my house
(the oldest of which is an original Celeron, so no 486),
and "early 486" is better than "early x86" which can mean anything.

This does leave earlier x86 unmentioned,
but Linux hasn't targeted those in over a decade,
so they're out of scope anyway.

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
 man4/cpuid.4 | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/man4/cpuid.4 b/man4/cpuid.4
index bd883e6d3..0b38fabe3 100644
--- a/man4/cpuid.4
+++ b/man4/cpuid.4
@@ -69,7 +69,9 @@ .SH NOTES
 There is no support for CPUID functions that require additional
 input registers.
 .P
-Very old x86 CPUs don't support CPUID.
+Early i486 CPUs do not support the CPUID instruction;
+.\" arch/x86/kernel/cpuid.c cpuid_open()
+opening this device for those CPUs fails with EIO.
 .SH SEE ALSO
 .BR cpuid (1)
 .P
-- 
2.39.2

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Re: [PATCH] cpuid.4: note which CPUs don't support CPUID and what happens

[Alejandro Colomar]

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Hi,

On Thu, Jan 04, 2024 at 11:31:21PM +0100, наб wrote:
> "Early 486" comes from an uncited wikipedia table, added in
>   https://en.wikipedia.org/w/index.php?title=CPUID&diff=prev&oldid=592047209
>   https://en.wikipedia.org/w/index.php?title=CPUID&diff=prev&oldid=592047978
> but I spot-checked the rest of the table accurate to CPUs in my house
> (the oldest of which is an original Celeron, so no 486),
> and "early 486" is better than "early x86" which can mean anything.
> 
> This does leave earlier x86 unmentioned,
> but Linux hasn't targeted those in over a decade,
> so they're out of scope anyway.
> 
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>

Patch applied.  Thanks!

Have a lovely day,
Alex

> ---
>  man4/cpuid.4 | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/man4/cpuid.4 b/man4/cpuid.4
> index bd883e6d3..0b38fabe3 100644
> --- a/man4/cpuid.4
> +++ b/man4/cpuid.4
> @@ -69,7 +69,9 @@ .SH NOTES
>  There is no support for CPUID functions that require additional
>  input registers.
>  .P
> -Very old x86 CPUs don't support CPUID.
> +Early i486 CPUs do not support the CPUID instruction;
> +.\" arch/x86/kernel/cpuid.c cpuid_open()
> +opening this device for those CPUs fails with EIO.
>  .SH SEE ALSO
>  .BR cpuid (1)
>  .P
> -- 
> 2.39.2



-- 
<https://www.alejandro-colomar.es/>
Looking for a remote C programming job at the moment.

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