linux-kernel - Re: [PATCH 6/8] MIPS: Limit MIPS_MT

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Date: Wed, 15 May 2024 22:26:16 +0100
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
 "Nathan Chancellor" <nathan@...nel.org>,
 "Nick Desaulniers" <ndesaulniers@...gle.com>,
 "Bill Wendling" <morbo@...gle.com>, "Justin Stitt" <justinstitt@...gle.com>,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
 "Guenter Roeck" <linux@...ck-us.net>
Subject: Re: [PATCH 6/8] MIPS: Limit MIPS_MT_SMP support by ISA reversion

在2024年5月15日五月 下午2:43，Maciej W. Rozycki写道：
> On Wed, 15 May 2024, Jiaxun Yang wrote:
>
>> >> MIPS MT ASE is only available on ISA between Release 1 and Release 5.
>> >
>> >  R2+ only actually, as also evident from Kconfig...
>> 
>> Hi Maciej,
>> 
>> Long time no see :-)
>
>  It's not so easy to get rid of me. ;)
>
>> There is nothing stopping us to run R1 kernel on R2 hardware, given that
>> those features are all detected at boot time. I understand MT was introduced
>> at 34K which is R2.
>
>  We can certainly choose to support R2 features at run time with R1 kernel 
> configurations, but it's not what the change description says (left quoted 
> above for reference).  And the MT ASE, indeed first implemented with the 
> 34K (for which I was a member of the product development team back at MIPS 
> UK), is not a part of the R1 ISA specification set.
>
Good to know!

The motivation behind this patch is to workaround some randconfig failures
that combines MT with early ISA release.

They are not trivial to fix, so I just ban them in Kconfig. I was a little bit
reluctant to admit that in commit message.

Anyway, thanks for bringing that up.

-- 
- Jiaxun