Re: Regression in 028abd92 for Sun UltraSPARC T1

[Frank Scheiner <frank.scheiner@web.de>]

Hi,

On 22.03.21 22:48, John Paul Adrian Glaubitz wrote:
> On 3/22/21 10:30 PM, Frank Scheiner wrote:
>> Riccardo Mottola first recognized a problem with 5.10.x kernels on his
>> Sun T2000 with UltraSPARC T1 (details in [this thread]). I could verify
>> the problem also on my Sun T1000 and it looks like this specific issue
>> breaks the mounting of the root FS or maybe mounting file systems at
>> all. This affects both booting from disk and from network.
>> (...)
>> ...as first bad commit.
>>
>> ```
>> commit 028abd9222df0cf5855dab5014a5ebaf06f90565
>> Author: Christoph Hellwig <hch@lst.de>
>> Date:   Thu Sep 17 10:22:34 2020 +0200
>>
>>      fs: remove compat_sys_mount
>>
>>      compat_sys_mount is identical to the regular sys_mount now, so
>> remove it
>>      and use the native version everywhere.
>> ```
>>
>> [1]:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=028abd9222df0cf5855dab5014a5ebaf06f90565
>
> Looking at this change, I think it's rather unexpected that this particular
> change would break the kernel on a specific CPU target. Are you sure that
> this is the right bad commit?

Well, I strictly followed the `git bisect` process and tested each and
every proposed revision. It's indeed strange that this only affects
UltraSPARC T1s, but the changes match the behavior: mounting of (root)
FS is broken.

> If you found the right commit, then I assume there is something wrong with
> the syscall handling on UltraSPARC T1.

Could be, all in all the T1 is a first of its kind.

Cheers,
Frank