From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D966FC4CEC9 for ; Wed, 18 Sep 2019 13:42:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A182A208C0 for ; Wed, 18 Sep 2019 13:42:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ellerman.id.au header.i=@ellerman.id.au header.b="OwZKzVnP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730513AbfIRNmF (ORCPT ); Wed, 18 Sep 2019 09:42:05 -0400 Received: from ozlabs.org ([203.11.71.1]:41717 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727648AbfIRNmE (ORCPT ); Wed, 18 Sep 2019 09:42:04 -0400 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 46YLkJ3x8Wz9sNf; Wed, 18 Sep 2019 23:42:00 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ellerman.id.au; s=201909; t=1568814121; bh=PKzP62Nhvc6oxy8JJMN0bYExGBIfXoqSAQasn8gwXuA=; h=From:To:Subject:In-Reply-To:References:Date:From; b=OwZKzVnPPxA/NqCnMz3jRwzgz5VkboxsZdCsDilcuaqGxXSQzkug+SKu50ElyRH41 aL4CgFQi2yvWq6iSWNuhCtFEbF20uXeVpqyCr62hregLFjlOSeLU9CzyBYZI1S6CSM S+gNF2LSQ4GC9DhFumiyQ2at54xiVQaw5dpGYcpedPgVbfaEvg0iYGVS/TnPSFv48V TeQXosEnhhLTJ5cm4835fEpfiVOyBoFA2LWCrFdQpO6gbrIwBOg0hxqeQlRYCFeb4S Utg9lzTO7IE0SQb5tT3WHGzQzIsEu0AlN1iUheMhYb4Hv3vkrRhUfQc4kBF8ufIzex gDL9gWKr4NGrQ== From: Michael Ellerman To: Laurent Dufour , benh@kernel.crashing.org, paulus@samba.org, aneesh.kumar@linux.ibm.com, npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/2] powerpc/mm: Conditionally call H_BLOCK_REMOVE In-Reply-To: <20190916095543.17496-1-ldufour@linux.ibm.com> References: <20190916095543.17496-1-ldufour@linux.ibm.com> Date: Wed, 18 Sep 2019 23:41:54 +1000 Message-ID: <871rwdwwkd.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent, Thanks for fixing this, just a few comments. Laurent Dufour writes: > Since the commit ba2dd8a26baa ("powerpc/pseries/mm: call H_BLOCK_REMOVE"), > the call to H_BLOCK_REMOVE is always done if the feature is exhibited. > > However, the hypervisor may not support all the block size for the hcall > H_BLOCK_REMOVE depending on the segment base page size and actual page > size. > > When unsupported block size is used, the hcall H_BLOCK_REMOVE is returning > H_PARAM, which is triggering a BUG_ON check leading to a panic like this: Missing panic :) Also can you put that detail in the 2nd commit, so that it's obvious that it is a fix for an oops. > The PAPR document specifies the TLB Block Invalidate Characteristics which Can you give a section/page number for the PAPR reference. > tells for each couple segment base page size, actual page size, the size of ^ "pair of" is better than "couple" I think > the block the hcall H_BLOCK_REMOVE is supporting. > > Supporting various block sizes doesn't seem needed at that time since all > systems I was able to play with was supporting an 8 addresses block size, > which is the maximum through the hcall, or none at all. Supporting various > size would complexify the algorithm in call_block_remove() so unless this > is required, this is not done. > > In the case of block size different from 8, a warning message is displayed > at boot time and that block size will be ignored checking for the > H_BLOCK_REMOVE support. > > Due to the minimal amount of hardware showing a limited set of > H_BLOCK_REMOVE supported page size, I don't think there is a need to push > this series to the stable mailing list. But the hardware that is exhibiting it, by crashing and not booting, is mostly (all?) older hardware. So I think we probably should send it back to stable, otherwise those machines may never get an updated kernel. Can you add Fixes: tags to the commits, they should point at the commit that added H_BLOCK_REMOVE support. cheers > The first patch is reading the characteristic through the hcall > ibm,get-system-parameter and record the supported block size for each page > size. The second patch is changing the check used to detect the > H_BLOCK_REMOVE availability to take care of the base page size and page > size couple. > > Changes since V1: > > - Remove penc initialisation, this is already done in > mmu_psize_set_default_penc() > - Add details on the TLB Block Invalidate Characteristics's buffer format > - Introduce #define instead of using direct numerical values > - Function reading the characteristics is now directly called from > pSeries_setup_arch() > - The characteristics are now stored in a dedciated table static to lpar.c > > Laurent Dufour (2): > powperc/mm: read TLB Block Invalidate Characteristics > powerpc/mm: call H_BLOCK_REMOVE when supported > > .../include/asm/book3s/64/tlbflush-hash.h | 1 + > arch/powerpc/platforms/pseries/lpar.c | 173 +++++++++++++++++- > arch/powerpc/platforms/pseries/setup.c | 1 + > 3 files changed, 173 insertions(+), 2 deletions(-) > > -- > 2.23.0