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 B499921C194; Wed, 12 Nov 2025 09:56:17 +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=1762941382; cv=none; b=ket+Grzwz4TSZTnUAdcEie4HFZCevdrXXwzgdtkzfDEr077gXdNIUmCE2MAs5q8imBusNSZDONd+dEprXhHwRC5ZJRE4OIu6v1N16lADJya8pPJ28rIaVe6iPbo5HVx87n4ohljzSiN5egqj0dJrd/OtfXbXpiIlAfgsovsbOpo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762941382; c=relaxed/simple; bh=8jt8rlBeGab/FL4KkfJu8liGWlNYNX8MU01la3kQr2Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JA1Y9u+0cU1gLmTWiNN62FDvaJJNxE7byP5wCkhIKLSrRmO5RejFU5C0RrcRB1TuGP7/wn4DiO3thOy2xofl1he49IxNlVkRNimg4WcqHGs50K18bKRaRxsU74lVsr2uU64z5opSyI4CyddSMB6ivg7Qp3aM+Y4AX5J+5sOWKpI= 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 1vJ7aJ-0003qh-00; Wed, 12 Nov 2025 10:56:15 +0100 Received: by alpha.franken.de (Postfix, from userid 1000) id C7825C0256; Wed, 12 Nov 2025 10:56:05 +0100 (CET) Date: Wed, 12 Nov 2025 10:56:05 +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 Tue, Nov 11, 2025 at 03:41:50PM +0000, Maciej W. Rozycki wrote: > On Tue, 11 Nov 2025, Thomas Bogendoerfer wrote: > > > > Can you please give it a try with your systems? > > > > it's booting on my R4400 SGI Indy, but I see a lot of segmentation > > faults during system start. If I comment out r4k_tlb_uniquify() every- > > thing boots fine, which is kind of strange as there is a local_flush_tlb_all(), > > which should leave the TLB in the same stage.... No idea why, yet. > > 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 :-( Do you want to send a v2 of the patch ? I'm fine with the current version for applying... Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]