From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id 9791F6B0424 for ; Wed, 21 Jun 2017 13:16:05 -0400 (EDT) Received: by mail-lf0-f72.google.com with SMTP id 24so23480lfr.10 for ; Wed, 21 Jun 2017 10:16:05 -0700 (PDT) Received: from mail-lf0-x243.google.com (mail-lf0-x243.google.com. [2a00:1450:4010:c07::243]) by mx.google.com with ESMTPS id x5si8876200lfa.188.2017.06.21.10.16.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Jun 2017 10:16:03 -0700 (PDT) Received: by mail-lf0-x243.google.com with SMTP id l200so11132406lfg.1 for ; Wed, 21 Jun 2017 10:16:03 -0700 (PDT) Date: Wed, 21 Jun 2017 20:15:58 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCHv2 1/3] x86/mm: Provide pmdp_establish() helper Message-ID: <20170621171558.7zrgzc7uk3kspcys@node.shutemov.name> References: <20170615145224.66200-1-kirill.shutemov@linux.intel.com> <20170615145224.66200-2-kirill.shutemov@linux.intel.com> <20170619152228.GE3024@e104818-lin.cambridge.arm.com> <20170619160005.wgj4nymtj2nntfll@node.shutemov.name> <20170619170911.GF3024@e104818-lin.cambridge.arm.com> <20170619215210.2crwjou3sfdcj73d@node.shutemov.name> <20170620155438.GC21383@e104818-lin.cambridge.arm.com> <20170621095303.q5fqt5a3ao5smko6@node.shutemov.name> <20170621112702.GC10220@e104818-lin.cambridge.arm.com> <1af1738a-88a7-987c-eca7-2118d66514e1@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1af1738a-88a7-987c-eca7-2118d66514e1@synopsys.com> Sender: owner-linux-mm@kvack.org List-ID: To: Vineet Gupta Cc: Catalin Marinas , "Kirill A. Shutemov" , Andrew Morton , Vlastimil Babka , Russell King , Will Deacon , Ralf Baechle , "David S. Miller" , "Aneesh Kumar K . V" , Martin Schwidefsky , Heiko Carstens , Andrea Arcangeli , "linux-arch@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Ingo Molnar , "H . Peter Anvin" , Thomas Gleixner On Wed, Jun 21, 2017 at 08:49:03AM -0700, Vineet Gupta wrote: > On 06/21/2017 04:27 AM, Catalin Marinas wrote: > > On Wed, Jun 21, 2017 at 12:53:03PM +0300, Kirill A. Shutemov wrote: > > > > > > > > On Thu, Jun 15, 2017 at 05:52:22PM +0300, Kirill A. Shutemov wrote: > > > > > > > > > We need an atomic way to setup pmd page table entry, avoiding races with > > > > > > > > > CPU setting dirty/accessed bits. This is required to implement > > > > > > > > > pmdp_invalidate() that doesn't loose these bits. > > [...] > > > Any chance you could help me with arm too? > > On arm (ARMv7 with LPAE) we don't have hardware updates of the > > access/dirty bits, so a generic implementation would suffice. I didn't > > find one in your patches, so here's an untested version: > > > > static inline pmd_t pmdp_establish(struct mm_struct *mm, unsigned long address, > > pmd_t *pmdp, pmd_t pmd) > > { > > pmd_t old_pmd = *pmdp; > > set_pmd_at(mm, address, pmdp, pmd); > > return old_pmd; > > } > > So it seems the discussions have settled down and pmdp_establish() can be > implemented in generic way as above and it will suffice if arch doesn't have > a special need. It would be nice to add the comment above generic version > that it only needs to be implemented if hardware sets the accessed/dirty > bits ! > > Then nothing special is needed for ARC - right ? I will define generic version as Catalin proposed with a comment, but under the name generic_pmdp_establish. An arch can make use of it by #define pmdp_establish generic_pmdp_establish I don't want it to be used by default without attention from architecture maintainer. It can lead unnoticied breakage if THP got enabled on new arch. -- Kirill A. Shutemov -- 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