linux-kernel - Re: [PATCH] drm/ttm: provide default page protection for UML

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Message-ID: <347e4cb8-a7c5-9e1b-16bc-96805442d35b@cambridgegreys.com>
Date:   Thu, 2 Sep 2021 09:10:54 +0100
From:   Anton Ivanov <anton.ivanov@...bridgegreys.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org
Cc:     Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>,
        Christian König <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>, dri-devel@...ts.freedesktop.org,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        linux-um@...ts.infradead.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/ttm: provide default page protection for UML

On 02/09/2021 08:43, Johannes Berg wrote:
> On Thu, 2021-09-02 at 07:19 +0100, Anton Ivanov wrote:
>>>>
>>>> I have a question though - why all of DRM is not !UML in config. Not
>>>> like we can use them.
>>>
>>> I have no idea about that.
>>> Hopefully one of the (other) UML maintainers can answer you.
>>
>> Touche.
>>
>> We will discuss that and possibly push a patch to !UML that part of the
>> tree. IMHO it is not applicable.
> 
> As I just said on the other patch, all of this is fallout from my commit
> 68f5d3f3b654 ("um: add PCI over virtio emulation driver") which is the
> first time that you could have PCI on UML.
> 
> Without having checked, in this particular case it's probably something
> like
> 
> 	depends on PCI && X86_64
> 
> as we've seen in other drivers (idxd, ioat).
> 
> The biggest problem is probably that UML internally uses X86_64
> (arch/x86/um/Kconfig), which is ... unexpected ... since CONFIG_X86_64
> is typically considered the ARCH, and now the ARCH is actually um.
> 
> I think we can just fix that and get rid of this entire class of
> problems? Something like
> 
> https://p.sipsolutions.net/fbac19d86637e286.txt

Good idea. I suspect that DRM will not be the only thing to pop up out 
of this so we might as well fix it "at the top".

A

> 
> johannes
> 
> 
> 
> _______________________________________________
> linux-um mailing list
> linux-um@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-um
> 

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

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