linux-kernel - Re: [BUG] dma-mapping: remove CONFIG_DMA

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Date:   Tue, 21 Jun 2022 16:19:24 +0200
From:   Christoph Hellwig <hch@....de>
To:     Mark Hounschell <markh@...pro.net>
Cc:     Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        Linux-kernel <linux-kernel@...r.kernel.org>,
        dmaengine@...r.kernel.org
Subject: Re: [BUG] dma-mapping: remove CONFIG_DMA_REMAP

On Tue, Jun 21, 2022 at 10:06:59AM -0400, Mark Hounschell wrote:
> On 6/21/22 09:48, Christoph Hellwig wrote:
>> On Tue, Jun 21, 2022 at 09:43:18AM -0400, Mark Hounschell wrote:
>>> Revert that commit and all works like normal. This commit breaks user land.
>>
>> No.  We had that discussion before.  It exposeѕ how broken your out of
>> tree driver is, which you don't bother to fix despite Robin even taking
>> the pains to explain you how.
>
> No, this is not the original issue and we never actually had a discussion. 
> That original issue was about using Set/ClearPageReserved. You nor Robin 
> even tried to explain why it was wrong to use it. It was never an issue in 
> previous kernels. Why now? In any case I have removed that code. This is 
> what happens now.
>
> What is it you think I am doing wrong. Except for using 
> Set/ClearPageReserved you have not explained anything to me.

Which part of "you must not call virt_to_page on the result that is
very clearly stated in the documentation and has been explained to
you repeatly" is still not clear to you?

Which part of "if your of tree modules stops working, this does not
constitute userspace breakage" is not clear to you?

I'm done with this, please stop bothering me.