linux-kernel - Re: [RFC PATCH] powerpc/tlb: enable arch want batched unmap tlb flush

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Message-ID: <87ldznreka.fsf@mail.lhotse>
Date: Thu, 19 Sep 2024 22:52:21 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Luming Yu <luming.yu@...ngroup.cn>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
 npiggin@...il.com, christophe.leroy@...roup.eu, jialong.yang@...ngroup.cn,
 luming.yu@...il.com
Subject: Re: [RFC PATCH] powerpc/tlb: enable arch want batched unmap tlb flush

Luming Yu <luming.yu@...ngroup.cn> writes:
> On Thu, Sep 19, 2024 at 01:22:21PM +1000, Michael Ellerman wrote:
>> Luming Yu <luming.yu@...ngroup.cn> writes:
>> > From: Yu Luming <luming.yu@...il.com>
>> >
>> > ppc always do its own tracking for batch tlb.
>> 
>> I don't think it does? :)
>> 
>> I think you're referring to the batch handling in 
>> arch/powerpc/include/asm/book3s/64/tlbflush-hash.h ?
>> 
>> But that's only used for 64-bit Book3S with the HPT MMU.
>> 
>> > By trivially enabling
>> > the ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH in ppc, ppc arch can re-use
>> > common code in rmap and reduce overhead and do optimization it could not
>> > have without a tlb flushing context at low architecture level.
>> >
>> > Signed-off-by: Luming Yu <luming.yu@...ngroup.cn>
>> > ---
>> >  arch/powerpc/Kconfig                |  1 +
>> >  arch/powerpc/include/asm/tlbbatch.h | 30 +++++++++++++++++++++++++++++
>> >  2 files changed, 31 insertions(+)
>> >  create mode 100644 arch/powerpc/include/asm/tlbbatch.h
>> 
>> This doesn't build:
>> 
>>   https://github.com/linuxppc/linux-snowpatch/actions/runs/10919442655
>> 
>> Can you please follow the instructions here:
>> 
>>   https://github.com/linuxppc/wiki/wiki/Testing-with-GitHub-Actions
>> 
>> Which describe how to fork our CI tree that has Github Actions
>> preconfigured, then you can apply your patches on top and push to github
>> and it will do some test builds for you. Notably it will do 32-bit
>> builds which is what broke here.

> thanks, I will take a look and do this for next patch before posting on mailing list. :-)
> 
> Ideally it should also include qemu boot tests for targets that must work.
 
Those scripts do qemu boots of pseries p8/p9, powernv p8/p9, 44x,
e5500, g5, and mac99.

It doesn't boot full distros because that's too slow for Github Actions,
so it doesn't catch all bugs, but it's better than nothing.

> I think we could also need a powerpc yocto recipe as well to make
> patch test more customizable
> and reproducible than fedora/Debian distro. I've been searching for it
> for a while, but I couldn't find a useful one. Maybe I need to come up
> one of my own to facilitate the ci test bot ideas.

I've never used Yocto, not sure if it does/did support powerpc.

Buildroot can build powerpc images with lots of packages included.

cheers