From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 7EF5A6B0038 for ; Thu, 16 Mar 2017 20:45:21 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id u108so11148396wrb.3 for ; Thu, 16 Mar 2017 17:45:21 -0700 (PDT) Received: from mail-wm0-x242.google.com (mail-wm0-x242.google.com. [2a00:1450:400c:c09::242]) by mx.google.com with ESMTPS id o184si861410wma.92.2017.03.16.17.45.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 16 Mar 2017 17:45:20 -0700 (PDT) Received: by mail-wm0-x242.google.com with SMTP id z133so905973wmb.2 for ; Thu, 16 Mar 2017 17:45:19 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1489680335-6594-1-git-send-email-jglisse@redhat.com> <1489680335-6594-8-git-send-email-jglisse@redhat.com> <20170316160520.d03ac02474cad6d2c8eba9bc@linux-foundation.org> From: Balbir Singh Date: Fri, 17 Mar 2017 11:45:19 +1100 Message-ID: Subject: Re: [HMM 07/16] mm/migrate: new memory migration helper for use with device memory v4 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: John Hubbard Cc: Andrew Morton , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , "linux-kernel@vger.kernel.org" , linux-mm , Naoya Horiguchi , David Nellans , Evgeny Baskakov , Mark Hairgrove , Sherry Cheung , Subhash Gutti On Fri, Mar 17, 2017 at 11:22 AM, John Hubbard wrote: > On 03/16/2017 04:05 PM, Andrew Morton wrote: >> >> On Thu, 16 Mar 2017 12:05:26 -0400 J=C3=A9r=C3=B4me Glisse >> wrote: >> >>> +static inline struct page *migrate_pfn_to_page(unsigned long mpfn) >>> +{ >>> + if (!(mpfn & MIGRATE_PFN_VALID)) >>> + return NULL; >>> + return pfn_to_page(mpfn & MIGRATE_PFN_MASK); >>> +} >> >> >> i386 allnoconfig: >> >> In file included from mm/page_alloc.c:61: >> ./include/linux/migrate.h: In function 'migrate_pfn_to_page': >> ./include/linux/migrate.h:139: warning: left shift count >=3D width of t= ype >> ./include/linux/migrate.h:141: warning: left shift count >=3D width of t= ype >> ./include/linux/migrate.h: In function 'migrate_pfn_size': >> ./include/linux/migrate.h:146: warning: left shift count >=3D width of t= ype >> > > It seems clear that this was never meant to work with < 64-bit pfns: > > // migrate.h excerpt: > #define MIGRATE_PFN_VALID (1UL << (BITS_PER_LONG_LONG - 1)) > #define MIGRATE_PFN_MIGRATE (1UL << (BITS_PER_LONG_LONG - 2)) > #define MIGRATE_PFN_HUGE (1UL << (BITS_PER_LONG_LONG - 3)) > #define MIGRATE_PFN_LOCKED (1UL << (BITS_PER_LONG_LONG - 4)) > #define MIGRATE_PFN_WRITE (1UL << (BITS_PER_LONG_LONG - 5)) > #define MIGRATE_PFN_DEVICE (1UL << (BITS_PER_LONG_LONG - 6)) > #define MIGRATE_PFN_ERROR (1UL << (BITS_PER_LONG_LONG - 7)) > #define MIGRATE_PFN_MASK ((1UL << (BITS_PER_LONG_LONG - PAGE_SHIFT= )) > - 1) > > ...obviously, there is not enough room for these flags, in a 32-bit pfn. > > So, given the current HMM design, I think we are going to have to provide= a > 32-bit version of these routines (migrate_pfn_to_page, and related) that = is > a no-op, right? Or make the HMM Kconfig feature 64BIT only by making it depend on 64BIT? Balbir Singh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org