Re: git: 80e4ac2964a1 - main - Work around VNET and DPCPU related panics on aarch64

From: Dimitry Andric <dim_at_FreeBSD.org>
Date: Mon, 24 Jul 2023 11:06:54 UTC
On 24 Jul 2023, at 00:48, Jessica Clarke <jrtc27@freebsd.org> wrote:
> 
> On 23 Jul 2023, at 23:38, Dimitry Andric <dim@FreeBSD.org> wrote:
>> 
>> The branch main has been updated by dim:
>> 
>> URL: https://cgit.FreeBSD.org/src/commit/?id=80e4ac2964a11edef456a15b77e43aadeaf273a2
>> 
>> commit 80e4ac2964a11edef456a15b77e43aadeaf273a2
>> Author:     Dimitry Andric <dim@FreeBSD.org>
>> AuthorDate: 2023-07-23 13:48:36 +0000
>> Commit:     Dimitry Andric <dim@FreeBSD.org>
>> CommitDate: 2023-07-23 22:35:04 +0000
>> 
>>   Work around VNET and DPCPU related panics on aarch64
>> 
>>   lld >= 14 and recent GNU ld can relax adrp+add and adrp+ldr
>>   instructions, which breaks VNET and DPCPU when used in modules.
> 
> Thanks for committing the workaround.
> 
> This will need some kind of EN for 13.2 given LLVM 14 was merged in
> time for that and arm64 is a Tier 1 architecture in 13.
> 
> There perhaps also needs to be some serious thought into our testing
> and release procedures given we allowed a Tier 1 architecture to have
> VNET and DPCU be totally broken in a point release for any kernel
> module. Especially when the bug was known, open against -CURRENT and
> triaged all before the MFC to stable/13; there needs to be better
> tracking of toolchain release blockers.

I agree, but how many users does this affect? I am only a sporadic user
of aarch64 builds, but I never saw any panics, and apparently our CI
builders also do not see these.

So how often do these panics actually occur? Must you specifically use a
VNET feature to encounter them?

-Dimitry