From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id 992078E0004 for ; Sat, 8 Dec 2018 12:04:52 -0500 (EST) Received: by mail-pf1-f198.google.com with SMTP id s14so6106288pfk.16 for ; Sat, 08 Dec 2018 09:04:52 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id h5si5447629pgc.237.2018.12.08.09.04.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 08 Dec 2018 09:04:51 -0800 (PST) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wB8H3sav028988 for ; Sat, 8 Dec 2018 12:04:51 -0500 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0a-001b2d01.pphosted.com with ESMTP id 2p8ax540ev-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sat, 08 Dec 2018 12:04:50 -0500 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 8 Dec 2018 17:04:50 -0000 Subject: Re: [PATCH V4 0/3] * mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region References: <20181121092259.16482-1-aneesh.kumar@linux.ibm.com> <20181207151226.cb00ace433738cf550e66885@linux-foundation.org> From: "Aneesh Kumar K.V" Date: Sat, 8 Dec 2018 22:34:39 +0530 MIME-Version: 1.0 In-Reply-To: <20181207151226.cb00ace433738cf550e66885@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Message-Id: <7a14631d-8077-e20f-d8a9-740710406168@linux.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , Alexey Kardashevskiy , mpe@ellerman.id.au, paulus@samba.org, David Gibson , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org On 12/8/18 4:42 AM, Andrew Morton wrote: > On Wed, 21 Nov 2018 14:52:56 +0530 "Aneesh Kumar K.V" wrote: > >> Subject: [PATCH V4 0/3] * mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region > > Asterisk in title is strange? My mistake while editing git-format-patch cover-letter. > >> ppc64 use CMA area for the allocation of guest page table (hash page table). We won't >> be able to start guest if we fail to allocate hash page table. We have observed >> hash table allocation failure because we failed to migrate pages out of CMA region >> because they were pinned. This happen when we are using VFIO. VFIO on ppc64 pins >> the entire guest RAM. If the guest RAM pages get allocated out of CMA region, we >> won't be able to migrate those pages. The pages are also pinned for the lifetime of the >> guest. >> >> Currently we support migration of non-compound pages. With THP and with the addition of >> hugetlb migration we can end up allocating compound pages from CMA region. This >> patch series add support for migrating compound pages. The first path adds the helper >> get_user_pages_cma_migrate() which pin the page making sure we migrate them out of >> CMA region before incrementing the reference count. > > Very little review activity. Perhaps Andrey and/or Michal can find the > time.. > >> mm/migrate.c | 108 ++++++++++++++++++++++++++++++++++++++++ > > can we make this code disappear when CONFIG_CMA=n? > We can definitely do static inline int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write, struct page **pages) { return get_user_pages_fast(start, nr_pages, write, pages); } with #ifdef CONFIG_CMA around but that is unnecessary #ifdef in the code. If CMA config is disabled, we will not be doing any migrate. Hence wondering whether we need an alternative definition for CONFIG_CMA=n -aneesh