2022-06-21 13:55:37

by Christoph Hellwig

[permalink] [raw]
Subject: Re: [BUG] dma-mapping: remove CONFIG_DMA_REMAP

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.


2022-06-21 14:21:29

by Mark Hounschell

[permalink] [raw]
Subject: Re: [BUG] dma-mapping: remove CONFIG_DMA_REMAP

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.

Mark

2022-06-21 14:37:30

by Christoph Hellwig

[permalink] [raw]
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.

2022-06-21 15:12:19

by Mark Hounschell

[permalink] [raw]
Subject: Re: [BUG] dma-mapping: remove CONFIG_DMA_REMAP

On 6/21/22 10:19, Christoph Hellwig wrote:
> 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?
>

That has not been explained to me at all. I am NOT any longer using
virt_to_page at all anywhere in the driver. I was told that
Set/ClearPageReserve was what I was doing wrong. Not that I was using
virt_to_page with it. I am not using either now. I am using only
dma_alloc_coherent.

> 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.

I am not trying to bother you and there is no reason for you to be rude
to me. I just think this is a bug and am trying to get to the bottom of it.

Regards
Mark