linux-kernel - Re: [PATCH] mm: Keep memory type same on DEVMEM Page-Fault

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Message-ID: <cacb6af0-27a8-8dc4-39dc-fc3936ea54eb@redhat.com>
Date:   Wed, 28 Jun 2023 11:10:34 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        "buddy.zhang" <buddy.zhang@...cuitos.cn>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Venkatesh Pallipadi <venki@...gle.com>,
        Suresh Siddha <sbsiddha@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Konstantin Khlebnikov <khlebnikov@...nvz.org>
Subject: Re: [PATCH] mm: Keep memory type same on DEVMEM Page-Fault

On 19.06.23 22:14, Andrew Morton wrote:
> On Sun, 16 Apr 2023 11:39:44 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
>> On Wed, 12 Apr 2023 14:22:36 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote:
>>
>>> On Sun, 19 Mar 2023 11:37:50 +0800 "buddy.zhang" <buddy.zhang@...cuitos.cn> wrote:
>>>
>>>> On X86 architecture, supports memory type on Page-table, such as
>>>> PTE is PAT/PCD/PWD, which can setup up Memory Type as WC/WB/WT/UC etc.
>>>> Then, Virtual address from userspace or kernel space can map to
>>>> same physical page, if each page table has different memory type,
>>>> then it's confused to have more memory type for same physical page.
>>>
>>> Thanks.  Nobody has worked on this code for a long time.  I'll cc a few
>>> folks who may be able to comment.
>>>
>>
>> Well that didn't go very well.
>>
>> Buddy, can you please explain what are the user-visible effects of the
>> bug?  Does the kernel crash?  Memory corruption, etc?  Thanks.
>>
> 
> Anyone?
> 

With a clear problem description, ad requested by you, I could be 
motivated to review this and understand the details :)

-- 
Cheers,

David / dhildenb