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 451E4C433EF for ; Fri, 6 May 2022 03:38:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 696E76B0071; Thu, 5 May 2022 23:38:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 644BB6B0073; Thu, 5 May 2022 23:38:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 50C9D6B0074; Thu, 5 May 2022 23:38:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 405DE6B0071 for ; Thu, 5 May 2022 23:38:33 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 0EE95206E1 for ; Fri, 6 May 2022 03:38:33 +0000 (UTC) X-FDA: 79433910906.11.9CE9954 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by imf18.hostedemail.com (Postfix) with ESMTP id B484E1C0009 for ; Fri, 6 May 2022 03:38:23 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=30;SR=0;TI=SMTPD_---0VCPvMM9_1651808302; Received: from 30.32.96.193(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VCPvMM9_1651808302) by smtp.aliyun-inc.com(127.0.0.1); Fri, 06 May 2022 11:38:24 +0800 Message-ID: <21b11024-e893-8c11-9b98-ab1d13413b61@linux.alibaba.com> Date: Fri, 6 May 2022 11:39:05 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH 2/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when migration To: Mike Kravetz , akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org Cc: tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org References: <11b92502b3df0e0bba6a1dc71476d79cab6c79ba.1651216964.git.baolin.wang@linux.alibaba.com> <5cab0eca-9630-a7c6-4f5d-5cb45ff82c83@oracle.com> From: Baolin Wang In-Reply-To: <5cab0eca-9630-a7c6-4f5d-5cb45ff82c83@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: j4s18au8d4mtgpadzs3d8bjk5qyrfhih Authentication-Results: imf18.hostedemail.com; dkim=none; spf=pass (imf18.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.132 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B484E1C0009 X-HE-Tag: 1651808303-154562 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 5/6/2022 7:53 AM, Mike Kravetz wrote: > On 4/29/22 01:14, Baolin Wang wrote: >> On some architectures (like ARM64), it can support CONT-PTE/PMD size >> hugetlb, which means it can support not only PMD/PUD size hugetlb: >> 2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page >> size specified. > >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 6fdd198..7cf2408 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1924,13 +1924,15 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, >> break; >> } >> } >> + >> + /* Nuke the hugetlb page table entry */ >> + pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); >> } else { >> flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); >> + /* Nuke the page table entry. */ >> + pteval = ptep_clear_flush(vma, address, pvmw.pte); >> } >> > > On arm64 with CONT-PTE/PMD the returned pteval will have dirty or young set > if ANY of the PTE/PMDs had dirty or young set. Right. > >> - /* Nuke the page table entry. */ >> - pteval = ptep_clear_flush(vma, address, pvmw.pte); >> - >> /* Set the dirty flag on the folio now the pte is gone. */ >> if (pte_dirty(pteval)) >> folio_mark_dirty(folio); >> @@ -2015,7 +2017,10 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, >> pte_t swp_pte; >> >> if (arch_unmap_one(mm, vma, address, pteval) < 0) { >> - set_pte_at(mm, address, pvmw.pte, pteval); >> + if (folio_test_hugetlb(folio)) >> + set_huge_pte_at(mm, address, pvmw.pte, pteval); > > And, we will use that pteval for ALL the PTE/PMDs here. So, we would set > the dirty or young bit in ALL PTE/PMDs. > > Could that cause any issues? May be more of a question for the arm64 people. I don't think this will cause any issues. Since the hugetlb can not be split, and we should not lose the the dirty or young state if any subpages were set. Meanwhile we already did like this in hugetlb.c: pte = huge_ptep_get_and_clear(mm, address, ptep); tlb_remove_huge_tlb_entry(h, tlb, ptep, address); if (huge_pte_dirty(pte)) set_page_dirty(page);