@kernellogger@fosstodon.org
@kernellogger@fosstodon.org avatar

kernellogger

@kernellogger@fosstodon.org

Mainly tooting about #Linux the #kernel and things related to the #LinuxKernel – e.g. #bootloader, #compiler, #git, #glibc, #mesa, #qemu, #xorg, #X11, #wayland, and other stuff in the 'plumbing' layer.

Opinions are my own.

Topic account. Other accounts of mine:

https://social.linux.pizza/@knurd42 (EN): #FLOSS, #Fedora as well as Life, the Universe and Everything
https://norden.social/@thleemhuis (DE): Das Leben, das Universum und der ganze Rest
https://social.tchncs.de/@thleemhuisfoss (DE): #FLOSS

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kernellogger, to linux
@kernellogger@fosstodon.org avatar

Now merged for #Linux 6.10 as part of the main media merge[1]:

[1] https://git.kernel.org/torvalds/c/6fd600d742744dc7ef7fc65ca26daa2b1163158a

kernellogger, to linux
@kernellogger@fosstodon.org avatar

2024-05-10 8:22 report[1]

2024-05-10 13:04 a fix is proposed, which a bit later is confirmed to be working[2]; a msg stating "I'll send out the formal patch next week" follows a few hours later

2024-05-16 14:11 six days later the "Formal patch is still under internal review"[3]

🤨 🥴 😟 😠

[1] https://lore.kernel.org/all/D15TIIDIIESY.D1EKKJLZINMA@fairphone.com/
[2] https://lore.kernel.org/all/4d60ccf3-455d-4189-9100-d35488b00236@quicinc.com/
[3] https://lore.kernel.org/all/4d72f74a-b2eb-43d3-92a2-1311081ce72c@quicinc.com/

zzywysm, to random
@zzywysm@hachyderm.io avatar

Hey @kernellogger i wanted you to see this evidence of a possible regression in 6.8, an arm64 fpsimd commit may have caused a dm_crypt corruption issue: https://github.com/tpwrules/nixos-apple-silicon/issues/200

kernellogger,
@kernellogger@fosstodon.org avatar

@zzywysm

Sounds a lot like it. Ideally someone would confirm if (a) 6.9 is still affected and (b) if reverting the culprit fixes things

Want me to raise this upstream (ideally after someone checks the above, unless that would take days)?

kernellogger,
@kernellogger@fosstodon.org avatar

@zzywysm

Sure. But seems my message came not across, so let me rephrase:

Could anybody quickly test what I asked for earlier?

Want me to escalate his? I'm happy to do that, but then I become a man-in-the-middle, which has benefits and downsides.

kernellogger,
@kernellogger@fosstodon.org avatar

@zzywysm

added a comment to that bug, thx for pointing me there

LaF0rge, to linux
@LaF0rge@chaos.social avatar

Some code related to "PFCP offloading" or "PFCP tunneling" has just appeared in mainline linux. Oddly enougn PFCP is not a tunneling protocol, and the code itself claims its not implementing PFCP. Trying to find out more about it: https://lists.openwall.net/netdev/2024/05/15/95 #linux #3gpp #telecom - if anyone knows more, I am very curious.

kernellogger,
@kernellogger@fosstodon.org avatar

@pink @Bubu

not really, sorry; checking the threads with the patch submissions might uncover answer[1], but I suspect @LaF0rge has done that already.

[1] e.g. most of the threads these search finds https://lore.kernel.org/all/?q=%22Packet+Forwarding+Control+Protocol%22

kernellogger, to random
@kernellogger@fosstodon.org avatar

24.1.0 is out: https://lists.x.org/archives/xorg/2024-May/061654.html

It among others brings support for explicit sync. If you wonder what this is and why it's important, check out https://zamundaaa.github.io/wayland/2024/04/05/explicit-sync.html . Long story short: it among others enables better wayland support in Nvidia's drivers.

kernellogger, (edited ) to random
@kernellogger@fosstodon.org avatar

New C++ features in #GCC 14; @strudlzrout writes:

"'C++26 features

  • Trivial infinite loops and UB
  • Static storage for braced initializers
    […]

C++23 features

  • Deducing this
  • References in constant expressions
    […]

Defect report resolutions

  • stricter constinit
  • goto and trivially-initialized objects
    […]

Additional updates

  • More checking in templates
  • In-class variable template partial specializations
    […]

New and improved warnings

  • -Wnrvo added
    […]"'

https://developers.redhat.com/articles/2024/05/15/new-c-features-gcc-14

kernellogger, to linux
@kernellogger@fosstodon.org avatar

Theo de Raadt and Linus Torvalds are debating mseal(), a variant of OpenBSD's mimmutable() syscall – which might or might not be merged for 6.10, as can be seen from other parts of the discussion:

https://lore.kernel.org/all/CAHk-=wgsGCKvN0Db6ZRZqJwXQrmhZyWB6RmABaOp4DiZbXgNew@mail.gmail.com/T/#u

kernellogger,
@kernellogger@fosstodon.org avatar

@vbabka

😬

/me wonders what he should have written instead to somehow indicate what's happening while staying subtle at the same time -- "throwing words at each other" maybe?

kernellogger, to linux
@kernellogger@fosstodon.org avatar

The TPM bus encryption and integrity protection changes prepared by @jejb and @jarkko were merged for #Linux 6.10: https://git.kernel.org/torvalds/c/b19239143e393d4b52b3b9a17c7ac07138f2cfd4

"[…] The key pair on TPM side is generated from so called null random seed per power on of the machine [1]. This supports the TPM encryption of the hard drive by adding layer of protection against bus interposer attacks. […]"

[1 https://lore.kernel.org/linux-integrity/20240429202811.13643-1-James.Bottomley@HansenPartnership.com/

kernellogger, to linux
@kernellogger@fosstodon.org avatar

Linus added a farewell notice to the merge commit that removed alpha EV5 support from #Linux mainline (and thus for version 6.10): https://git.kernel.org/torvalds/c/736676f5c3abd1fc01c41813a95246e892937f6d #kernel #LinuxKernel

kernellogger, to linux
@kernellogger@fosstodon.org avatar

Hmm, looks like "NT synchronization primitive emulation" (#ntsync aka emulation of Windows NT synchronization primitives) a few people are really looking forward to and meant to be merged for #Linux #kernel 6.10 might be marked as broken for now (and thus would be impossible to enable) – at least it looks like this from this patch Greg posted, who maintains the subsystem the code resists in:

https://lore.kernel.org/all/2024051450-abrasion-swizzle-550b@gregkh/

kernellogger, to linux
@kernellogger@fosstodon.org avatar

The #kernel developers are wondering if anyone is still using the x32 user mode supported by x86-64 #Linux:

https://lore.kernel.org/all/20240514092746.GAZkMukkJ_q59aZQTH@fat_crate.local/

Related: https://lore.kernel.org/all/CAMe9rOoEQ3jUUXy+Kai9Hg83b+79azmGfu8DBR=A3HSL05kj0A@mail.gmail.com/ #LinuxKernel

kernellogger, to linux
@kernellogger@fosstodon.org avatar

The latest discussion about the extensible scheduler class (or "sched_ext") for the since yesterday is active again after a post from peterz:

https://lore.kernel.org/all/20240513080359.GI30852@noisy.programming.kicks-ass.net/t/#u

"'That is, from where I am sitting I see $vendor mandate their $enterprise product needs their $BPF scheduler. At which point $vendor will have no incentive to ever contribute back.

[…]

[…] GPL forces people to contribute back […] And I see the whole BPF thing as a run-around on that. '"

kernellogger, to linux
@kernellogger@fosstodon.org avatar

"'In this post, I’ll describe our track record in supporting Linux on laptops with Windows on Snapdragon and how that continues with the Snapdragon X Elite. You’ll see what’s already merged in the mainline #Linux #Kernel, what’s pending and what’s on our roadmap.

https://www.qualcomm.com/developer/blog/2024/05/upstreaming-linux-kernel-support-for-the-snapdragon-x-elite #LinuxKernel

kernellogger, to linux
@kernellogger@fosstodon.org avatar

A question for experts on #git bisecting the #Linux #Kernel:

Assume someone runs into a regression when updating from 6.1.90[1] to 6.6.30 that needs bisecting. What do you suggest:

  • Check manually which mainline release (e.g. 6.2, 6.3, ...) introduced the problem and afterwards bisect between that and the previous release.

  • Bisect straight between 6.1 and 6.6.30.

1/ I guess I would definitely go for…

[1] let's assume that 6.1 was fine for this scenario to keep things simpler

kernellogger,
@kernellogger@fosstodon.org avatar

2/ …the first option, if the user has access to pre-compiled kernel packages that make it easy to test those mainline releases (or stable kernels derived from it) .

But what's the better approach if the user has no such packages at hand?

kernellogger,
@kernellogger@fosstodon.org avatar

@klausman

Yeah, definitely.

Another dragon in that field: .config changes where the packager enabled some new feature (say a new security technique that is known to cause problems for some old apps) that causes a regression.

Is rare, but does happen.

kernellogger,
@kernellogger@fosstodon.org avatar

@gromit

out of curiosity: if you do that locally using the arch stuff, does it do a full rebuild for each step, or does building a new step build upon what the previous step left behind (which at the end of the build process makes quite a difference)

kernellogger,
@kernellogger@fosstodon.org avatar

@gromit

yeah, rpm start with a clean env as well, but when it comes to kernel bisections in can be a downside if you don't have a beefy buildserver at hand ;-)

If you update that or a related page, you might want to add a link to https://docs.kernel.org/admin-guide/verify-bugs-and-bisect-regressions.html somewhere if suitable (which does more than a bisection, but that almost always is wise)

kernellogger,
@kernellogger@fosstodon.org avatar

@poeschel

"I understand you want to avoid compiling the kernel at a first step, right?"

what? no. As you said yourself: the users has to set up everything anyway.

"spare much time testing precompiled kernels": I guess that likely depends a lot on the horsepower of your machine; on my T14s Gen1 AMD I think compiling a localmodconfig kernel takes 10 or 15 minutes; downloading and installing would be quicker, even if I'd have to do it somewhat manually

kernellogger,
@kernellogger@fosstodon.org avatar

@SchwarzeLocke

Well, sure, that's why I wrote " let's assume that 6.1 was fine for this scenario to keep things simpler"; apparently that was not clear enough, sorry.

kernellogger,
@kernellogger@fosstodon.org avatar

@SchwarzeLocke

and, yeah, doing the first steps manually might be a good compromise

kernellogger,
@kernellogger@fosstodon.org avatar

@SchwarzeLocke

Sometimes I think somebody should submit a patch to remove the trainling .0 from the versioning when it's ".0", as kernel.org and Linus also just call mainline releases "6.9". but whatever, that is just a detail -- and fixing it would likely break something.

kernellogger,
@kernellogger@fosstodon.org avatar

@SchwarzeLocke

Hmmm. Wondering if that is worth it, but yeah, it likely is. Will keep that in mind for the next time I work on that document.

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