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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3911AC38145 for ; Wed, 7 Sep 2022 19:34:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9A8106B0072; Wed, 7 Sep 2022 15:34:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9560C6B0073; Wed, 7 Sep 2022 15:34:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F7098D0002; Wed, 7 Sep 2022 15:34:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 6D26D6B0072 for ; Wed, 7 Sep 2022 15:34:22 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 46E77A1703 for ; Wed, 7 Sep 2022 19:34:22 +0000 (UTC) X-FDA: 79886290764.25.37FDA5C Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf23.hostedemail.com (Postfix) with ESMTP id 8DABA140082 for ; Wed, 7 Sep 2022 19:34:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1662579261; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7MsVI8c1fxq0sSSjaJXYEOch1npprYIC2451+xAyYa0=; b=iUjtBjWYDTJXmcZd3y7NVONygZYd715cujpPALtiXPzuOIPtqtY4E+VV/hzeTDzJAS4eIY wDHHZMJupcQZN7hJOZ07O9Ef5UuffmWTiggcPw2bGQYTVniOqNDlse32bhFAt3QJArl9yb o55zpBO8n4jAOtqGuo5+kS0NFheMtag= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-120-ZzAdZIDQM-eyCOsvs5HlwQ-1; Wed, 07 Sep 2022 15:34:19 -0400 X-MC-Unique: ZzAdZIDQM-eyCOsvs5HlwQ-1 Received: by mail-wr1-f70.google.com with SMTP id d11-20020adfc08b000000b002207555c1f6so3903170wrf.7 for ; Wed, 07 Sep 2022 12:34:19 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date; bh=7MsVI8c1fxq0sSSjaJXYEOch1npprYIC2451+xAyYa0=; b=kl76dmESu3HCUnOXG/FjwVk3YtaiPmk8qObCYa7qQ2g08Y9kRGBC/IwlCy9CIS6zPV XRVjCipmK64BqYNIYe9UtuIdDWTEd8/3QTrAhG4qsZFLAb0VUEkd7xMGeMe3BelPojOT jmZWyGnJHkByz/ZQ9SI6fp+jLveyH7A2erqJe8Whnm6VPH8Jx/cTlHnbYEot/MJPqszn Dw1RVhsfGzsXJWhtcziOGxf9F5SVscb75bxK7XySAuOaKNkyetO2aVJIzc9MvS6hWMUB 3JAMDPim79SWTbVD+rPvgGNkxiLJLfquysCkStftmLFnGgx2QUo1So5gX+P5iTrezq05 YGJA== X-Gm-Message-State: ACgBeo16XW+6WRN3ut/v8styua9XJOM3fSM09y4GCTLIvUfUtoTn8R34 0wJqdROcXCBtLLeZ/vAjC19AGAigPEj3bpOKgaMANzCHFeIJnb2c2V799wzQiBMdKbRwmoN9aoz O0/lrXpQIju4= X-Received: by 2002:adf:e9c2:0:b0:228:62a5:a59b with SMTP id l2-20020adfe9c2000000b0022862a5a59bmr3023776wrn.47.1662579257739; Wed, 07 Sep 2022 12:34:17 -0700 (PDT) X-Google-Smtp-Source: AA6agR47W6WNql5ZeWImeEUS0k3WgwW8frzlFbU39PqtW0jo90OD5KShj425J9bGCwCzIr1xpbbM3g== X-Received: by 2002:adf:e9c2:0:b0:228:62a5:a59b with SMTP id l2-20020adfe9c2000000b0022862a5a59bmr3023766wrn.47.1662579257500; Wed, 07 Sep 2022 12:34:17 -0700 (PDT) Received: from ?IPV6:2003:d8:2f0d:ba00:c951:31d7:b2b0:8ba0? (p200300d82f0dba00c95131d7b2b08ba0.dip0.t-ipconnect.de. [2003:d8:2f0d:ba00:c951:31d7:b2b0:8ba0]) by smtp.gmail.com with ESMTPSA id bz9-20020a056000090900b0022584c82c80sm19260207wrb.19.2022.09.07.12.34.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Sep 2022 12:34:17 -0700 (PDT) Message-ID: <684b9004-fad2-3727-b215-a4b2bfe36712@redhat.com> Date: Wed, 7 Sep 2022 21:34:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [v2 PATCH 2/2] powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush To: Yang Shi , peterx@redhat.com, kirill.shutemov@linux.intel.com, jhubbard@nvidia.com, jgg@nvidia.com, hughd@google.com, akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20220907180144.555485-1-shy828301@gmail.com> <20220907180144.555485-2-shy828301@gmail.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220907180144.555485-2-shy828301@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662579261; a=rsa-sha256; cv=none; b=EwWcJLrama7KzEyBGV5aP4azf4F9IH4MXMWiBK/OpJT/1BTlpy1+YerYVpqlby45U9vf6j 8t6kfYLtsLhkZw2BN/BUb60lWGb2agZuXUnMdqd6KPKbBwCug3ZrfELvsWLRTxpn23kIVN UywtacxNHLfoUz1lynIjGhU8t9hfER8= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iUjtBjWY; spf=pass (imf23.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662579261; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7MsVI8c1fxq0sSSjaJXYEOch1npprYIC2451+xAyYa0=; b=lOo75JkU/RwWt49EDg8BGxUjoIgI2y1jkAZskqbl3Q+WsTKpQCSXB54kvjKZ9wY4+LhlDl xRZT/IAR7Wt4DD1VHEVtZ+fEobXthn2l3f3c6B6qfaq/WSsBgu/V+UjlDh25BpP2CLR4e9 5YlBO7Yc9PzgauHhpLPhnxTnqeidJII= X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iUjtBjWY; spf=pass (imf23.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam04 X-Stat-Signature: w51xrp8syzi3jp1jzqixtxx63b3x4xj8 X-Rspamd-Queue-Id: 8DABA140082 X-HE-Tag: 1662579261-349897 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 07.09.22 20:01, Yang Shi wrote: > The IPI broadcast is used to serialize against fast-GUP, but fast-GUP > will move to use RCU instead of disabling local interrupts in fast-GUP. > Using an IPI is the old-styled way of serializing against fast-GUP > although it still works as expected now. > > And fast-GUP now fixed the potential race with THP collapse by checking > whether PMD is changed or not. So IPI broadcast in radix pmd collapse > flush is not necessary anymore. But it is still needed for hash TLB. > > Suggested-by: Aneesh Kumar K.V > Signed-off-by: Yang Shi > --- > arch/powerpc/mm/book3s64/radix_pgtable.c | 9 --------- > 1 file changed, 9 deletions(-) > > diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c > index 698274109c91..e712f80fe189 100644 > --- a/arch/powerpc/mm/book3s64/radix_pgtable.c > +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c > @@ -937,15 +937,6 @@ pmd_t radix__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long addre > pmd = *pmdp; > pmd_clear(pmdp); > > - /* > - * pmdp collapse_flush need to ensure that there are no parallel gup > - * walk after this call. This is needed so that we can have stable > - * page ref count when collapsing a page. We don't allow a collapse page > - * if we have gup taken on the page. We can ensure that by sending IPI > - * because gup walk happens with IRQ disabled. > - */ > - serialize_against_pte_lookup(vma->vm_mm); > - > radix__flush_tlb_collapsed_pmd(vma->vm_mm, address); > > return pmd; Makes sense to me Acked-by: David Hildenbrand -- Thanks, David / dhildenb