linux-kernel - Re: [PATCH net-next v7 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

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Message-ID: <79a49ccd-b0c0-0b99-4b4d-c4a416d7e327@huawei.com>
Date:   Wed, 23 Aug 2023 11:03:31 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>
CC:     Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Mina Almasry <almasrymina@...gle.com>, <davem@...emloft.net>,
        <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Liang Chen <liangchen.linux@...il.com>,
        Alexander Lobakin <aleksander.lobakin@...el.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>
Subject: Re: [PATCH net-next v7 1/6] page_pool: frag API support for 32-bit
 arch with 64-bit DMA

On 2023/8/22 23:38, Jakub Kicinski wrote:
> On Tue, 22 Aug 2023 17:21:35 +0800 Yunsheng Lin wrote:
>>> .. we should also add a:
>>>
>>> 	WARN_ONCE(1, "misaligned DMA address, please report to netdev@");  
>>
>> As the CONFIG_PHYS_ADDR_T_64BIT seems to used widely in x86/arm/mips/powerpc,
>> I am not sure if we can really make the above assumption.
>>
>> https://elixir.free-electrons.com/linux/v6.4-rc6/K/ident/CONFIG_PHYS_ADDR_T_64BIT
> 
> Huh, it's actually used a lot less than I anticipated!
> 
> None of the x86/arm/mips/powerpc systems matter IMHO - the only _real_

Is there any particular reason that you think that the above systems does
not really matter?

As we have made a similar wrong assumption about those arches before, I am
really trying to be more cautious about it.

I searched through the web, some seems to be claiming that "32-bits is DEAD",
I am not sure if there is some common agreement among the kernel community,
is there any previous discussion about that?