Re: [PATCH 1/4] virtio_console: copy pipe buffers in splice_write()

[David Hildenbrand (Arm)]

On 11/12/26 09:55, Arnd Bergmann wrote:
> On Wed, Nov 11, 2026, at 20:26, Linus Torvalds wrote:
>> On Wed, 11 Nov 2026 at 10:53, Christian Brauner <brauner@xxxxxxxxxx> wrote:
>>>
>>> If that's the official new stance than I'm very happy.
>>
>> I definitely want to remove HIGHMEM entirely in the not too distant
>> future. And before we remove it, we can most definitely document the
>> fact that we will not be worried about insane users.
>>
>> And things like security issues count as "insane user": if you use
>> HIGHMEM outside of controlled embedded setups or museum pieces you get
>> to keep both pieces when it breaks.
>>
>> IOW, it's legacy. We should aim to not introduce *new* bugs to it, but
>> if there are pre-existing bugs they very much count as "don't care",
>> this will be removed soon.
> 
> Agreed. There is also the option of adding Kconfig dependencies to
> mark things that are known broken with highmem when we either know
> that it is buggy, or we have a good reason to break something that
> none of those remaining users should be using.
> 
>> I think the only reason it wasn't removed a couple of years ago
>> already is basically a few old 32-bit ARM platforms that still used
>> it.
>>
>> Those platforms still exist, and I predict that they'll still exist
>> next year, but if those users have to stay at the current LTS kernel,
>> that's fine.
> 
> I tried to push for what I thought was an aggressive timeline
> last year, but that would still keep the Arm bits for a couple more
> LTS releases and only gradually reduce the scope of highmem in the
> meantime, removing support from architectures, file systems, and
> drivers where possible. See https://lwn.net/Articles/1051010/
> for a summary of my talk in Tokyo, including the slides and
> a link to the video for anyone wanting more details.
> 
> I also prepared a number of patches towards this, but have so
> far not been great at following up to get them merged, sorry
> about that.

I think we can already start at removing CONFIG_HIGHPTE now, right?

-- 
Cheers,

David