linux-kernel - Re: [PATCH V4 2/2] riscv: Use use_asid

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Date:   Mon, 31 May 2021 08:36:58 +0200
From:   Christoph Hellwig <hch@....de>
To:     palmerdabbelt@...gle.com
Cc:     Christoph Hellwig <hch@....de>, guoren@...nel.org,
        Anup Patel <Anup.Patel@....com>, Arnd Bergmann <arnd@...db.de>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-sunxi@...ts.linux.dev,
        guoren@...ux.alibaba.com
Subject: Re: [PATCH V4 2/2] riscv: Use use_asid_allocator flush TLB

On Sat, May 29, 2021 at 04:42:37PM -0700, palmerdabbelt@...gle.com wrote:
>>
>> Also the non-ASID code switches to a global flush once flushing more
>> than a single page.  It might be worth documenting the tradeoff in the
>> code.
>
> For some reason I thought we'd written this down in the commentary of teh 
> ISA manual as the suggested huersitic here, but I can't find it so maybe 
> I'm wrong.  If it's actually there it would be good to point that out, 
> otherwise some documentation seems fine as it'll probably become a tunable 
> at some point anyway.

The real question is why is the heuristic different for the ASID vs
non-ASID case?  I think that really need a comment.

> LGTM.  I took the first one as IMO they're really distnict issues, LMK if 
> you want to re-spin this one or if I should just take what's here.

What distinct issue?  The fact that the new code is buggy and uses rather
non-optimal calling conventions?