Bug#1109776: Support for non-4kB pages in Xe driver

From	Simon Richter <sjr@debian.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1109776: Support for non-4kB pages in Xe driver
Date	2025-07-23 18:50 +0200
Message-ID	<LbKPf-266W-5@gated-at.bofh.it> (permalink)
References	<LbJTb-25ug-1@gated-at.bofh.it> <LbKcx-25R8-3@gated-at.bofh.it> <LbJTb-25ug-1@gated-at.bofh.it> <LbKcx-25R8-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Hi,

On 7/24/25 00:59, Bastian Blank wrote:

>> this is a set of backported patches to make the Xe driver in the stable
>> kernel not Oops when run on a machine with a page size that isn't 4k.

> I see that patches on stable@, we won't take patches that can go this
> way usually.

The full patchset[1] for later kernels has a bunch of extra changes, but 
the stable kernel is old enough that we can get by with a number of 
simple substitutions:
  - replace SZ_4K with PAGE_SIZE when finding an alignment palatable to 
the CPU
  - replace PAGE_SIZE with SZ_4K when describing a memory layout in GPU 
memory that uses 4k alignment regardless of host page size.

So on 4k, where PAGE_SIZE *is* SZ_4K, this does nothing, but it fixes 
the Oops on boot for 16k (aarch64, loong64) and 64k (ppc64le) users.

Since these are derived from the proper fix, you can easily see when 
they are no longer required.

    Simon

[1] 
https://lore.kernel.org/all/20250604-upstream-xe-non-4k-v2-v2-0-ce7905da7b08@aosc.io/

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Bug#1109776: Support for non-4kB pages in Xe driver Bastian Blank <waldi@debian.org> - 2025-07-23 18:10 +0200
  Bug#1109776: Support for non-4kB pages in Xe driver Simon Richter <sjr@debian.org> - 2025-07-23 18:50 +0200

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