Linux 6.4-rc1 Released With Intel LAM, Several New AMD Features, More Rust Code & Early Apple M2

Written by Michael Larabel in Linux Kernel on 7 May 2023 at 05:34 PM EDT. 1 Comment
Linus Torvalds just released Linux 6.4-rc1 that also marks the end of the merge window for the exciting Linux 6.4 cycle.

Linus Torvalds wrote in this evening's 6.4-rc1 announcement:
"So here we are, two weeks later, with the merge window over, and -rc1 tagged and pushed out.

Things look pretty normal - the only somewhat unusual thing for me personally was that we had two different pull requests that ended up with me doing my own little series of updates on top.

So both the ITER_UBUF update from Jens, and the x86 LAM support from Dave Hansen (really Kirill, but I see the pull from Dave) caused me to do some extra x86 user access cleanups.

The reason I mention that isn't so much "oh, I got to code a bit again", but that this actually caused me to *finally* switch to a more modern default 'git diff' algorithm. The default git diff algorithm is the very traditional one (aka 'Myers algorithm'), and while it works just fine, there's been various heuristics updates to make for nicer diffs by default.

So I'm now using the 'histogram' algorithm, that takes the "uniqueness" of a line into account when deciding on longest common subsequence, because some of my patches were just an unreadable mess with the plain Myers diff. Not that histogram always helps, but it does often make things more legible.
As to the actual changes in this merge window: the mergelog below gives the high-level view. The diffstat is completely dominated by AMD GPU hardware description files once again, and this time the 'perf' tool has followed suite, and so the other big area ends up being all the perf event JSON file descriptions. Ugh.

But if you ignore those two "massive, but uninteresting" parts of the changes, everything else looks fairly normal. Lots of development all over, with "that's interesting" mainly depending on the reader. Drivers, architecture updates, filesystems, networking, memory management - there's a bit of everything.

The one feature that didn't make it was the x86 shadow stack code. That side was probably a bit unlucky, in that it came in as I was looking at x86 issues anyway, and so I looked at it quite a bit, and had enough reservations that I asked for a couple of fairly big re-organizations.

We'll get to that at a later date, possibly the next release."

I'll be out tomorrow with my usual Linux 6.4 feature overview that summarizes the dozens of Phoronix articles the past two weeks highlighting the numerous new features and other interesting bits of the kernel.

Linux 6.4-rc1

There's a lot of exciting stuff with Linux 6.4 and I'll be firing up some benchmarks shortly.

Update: The Linux 6.4 feature list has been posted.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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