From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from elvis.franken.de (elvis.franken.de [193.175.24.41]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C5C6C28B4E2; Wed, 12 Nov 2025 14:21:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.175.24.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762957269; cv=none; b=ECOEMhKVsZomOyOMe+U64xGlRleWsMaaxyHgb/D/9yy+0k8uU6GzM02fRnSXX3Rb2DqjR3xMCuOmV2lb4VdbAIB2MnqEoAM+JtItwRd5DCScQ0XBMQy9aCfwnAGQpkickNq+OGZrcrZAsF9ICxRv6mD0jBN5/4AmC4s1sLdYmaw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762957269; c=relaxed/simple; bh=SRYLvUDpCdqP6YtexjQVy4seZnryfA4m9OxdvHn18eM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iN+5A5NjsGJlmoEIp9X4LFlsrrXmZvxs7AJiS6CrgKaKlRvJO70VUkXPr5L3dl0UTJYFmV1CxnY3l6sETa1xWlE4vq9k8mCnvmmT2F1Z/YJu3zBW8170XsbcpoFK6SyUresvE9607pykPv7mYMdodPudFMj3J4goifkd7CtKl/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=alpha.franken.de; spf=pass smtp.mailfrom=alpha.franken.de; arc=none smtp.client-ip=193.175.24.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=alpha.franken.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=alpha.franken.de Received: from uucp by elvis.franken.de with local-rmail (Exim 3.36 #1) id 1vJBiY-0006j4-00; Wed, 12 Nov 2025 15:21:02 +0100 Received: by alpha.franken.de (Postfix, from userid 1000) id 5881BC0256; Wed, 12 Nov 2025 15:20:52 +0100 (CET) Date: Wed, 12 Nov 2025 15:20:52 +0100 From: Thomas Bogendoerfer To: "Maciej W. Rozycki" Cc: Nick Bowler , Jiaxun Yang , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] MIPS: mm: Prevent a TLB shutdown on initial uniquification Message-ID: References: Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Nov 12, 2025 at 12:16:28PM +0000, Maciej W. Rozycki wrote: > On Wed, 12 Nov 2025, Thomas Bogendoerfer wrote: > > > > Can you try the diagnostic patch below, which is what I used to verify > > > this change, and report the entries produced? Otherwise I wonder whether > > > I haven't missed a barrier somewhere. > > > > Update on the issue: Your patch is good and the segmentation faults, > > I'm seeing, have IMHO a different reason. Instead of removing the call > > to r4k_tlb_uniquify() I've replaced the jal in the binary with a nop. > > And the issue is still there with this patched kernel. I've seen > > something similair on a R12k Octanes, which comes and goes probably > > depeding on code layout. So far I wasn't able to nail this down :-( > > Oh dear! Something to do with the cache? Or code alignment perhaps? code alignment is probably the trigger. It's reproducible on an R4400SC and R5000 Indy, but not on a R4000SC Indy. Main difference other than clock speed is L1 cache size... And I've missremembered the R12k Octane problem. It's not a segmentation fault but a bus error, because of an illegal instruction. I tracked it down to a incorrect data in I-Cache (all 0 cache line, iirc), but never found the reason for that. > > Do you want to send a v2 of the patch ? I'm fine with the current version > > for applying... > > I'll send v2 with an update for the Wired register as we talked. It may > take a day or two. no problem, thank you. Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]