linux-kernel - Re: [PATCH v2 1/1] sparc: fix accurate exception reporting in copy_{from,to}

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Message-ID: <ydd4itm45p5.fsf@CeBiTec.Uni-Bielefeld.DE>
Date: Mon, 01 Sep 2025 16:18:14 +0200
From: Rainer Orth <ro@...iTec.Uni-Bielefeld.DE>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>,
  linux-kernel@...r.kernel.org,  sparclinux@...r.kernel.org,  Andreas
 Larsson <andreas@...sler.com>,  Anthony Yznaga <anthony.yznaga@...cle.com>
Subject: Re: [PATCH v2 1/1] sparc: fix accurate exception reporting in
 copy_{from,to}_user for M7

Hi Adrian,

> On Mon, 2025-09-01 at 09:00 +0200, Rainer Orth wrote:
>> > in the past, you reported stability issues with the Linux kernel when running
>> > inside an LDOM on SPARC M7/M8. Could you verify whether the patch above fixes
>> > these problems or whether at least they don't introduce regressions?
>> 
>> thanks for the heads-up.  Indeed the hangs persist even when the system
>> is idle.  However, I've never built a Linux kernel before and have way
>> too much on the plate to try now.  Besides, I don't have a reproducer
>> for the issue, so even with a patch I'd have to wait for an extended
>> period of time to see if the issue is gone, so I'll just wait until the
>> patch lands in the Debian/sparc64 repo and see if it helps.
>
> Would it work if I built a kernel for you plus installation instructions
> and a quick explanation how to test it?

I wouldn't mind trying, but as I said it's difficult to say when I can
claim success given the lack of a reproducer.  All I can report reliably
is failure ;-)

> FWIW, we consider the patch already acceptable when it doesn't introduce
> any regressions.
>
> I did some testing on a SPARC S7 yesterday, but the problem is that the
> support for SPARC S7 in the Linux kernel is incomplete at the moment and
> I had to add it quickly myself which did actually work but I really would
> like to verify it on M7 or M8 again to at least not cause regressions.

The only system that I can test on is S7 (a Netra S7-2 actually).  While
I also have a T8-1, that's reserved for cfarm work.

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University