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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6184DC47257 for ; Fri, 8 May 2020 19:51:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 44E7C24954 for ; Fri, 8 May 2020 19:51:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726906AbgEHTve (ORCPT ); Fri, 8 May 2020 15:51:34 -0400 Received: from verein.lst.de ([213.95.11.211]:54154 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726767AbgEHTve (ORCPT ); Fri, 8 May 2020 15:51:34 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 6EAA068C7B; Fri, 8 May 2020 21:51:30 +0200 (CEST) Date: Fri, 8 May 2020 21:51:30 +0200 From: Christoph Hellwig To: Ralph Campbell Cc: nouveau@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Jerome Glisse , John Hubbard , Christoph Hellwig , Jason Gunthorpe , Ben Skeggs , Andrew Morton , Shuah Khan , willy@infradead.org Subject: Re: [PATCH 4/6] mm/hmm: add output flag for compound page mapping Message-ID: <20200508195129.GA19740@lst.de> References: <20200508192009.15302-1-rcampbell@nvidia.com> <20200508192009.15302-5-rcampbell@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200508192009.15302-5-rcampbell@nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Fri, May 08, 2020 at 12:20:07PM -0700, Ralph Campbell wrote: > hmm_range_fault() returns an array of page frame numbers and flags for > how the pages are mapped in the requested process' page tables. The PFN > can be used to get the struct page with hmm_pfn_to_page() and the page size > order can be determined with compound_order(page) but if the page is larger > than order 0 (PAGE_SIZE), there is no indication that the page is mapped > using a larger page size. To be fully general, hmm_range_fault() would need > to return the mapping size to handle cases like a 1GB compound page being > mapped with 2MB PMD entries. However, the most common case is the mapping > size the same as the underlying compound page size. > Add a new output flag to indicate this so that callers know it is safe to > use a large device page table mapping if one is available. Why do you need the flag? The caller should be able to just use page_size() (or willys new thp_size helper). From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 4/6] mm/hmm: add output flag for compound page mapping Date: Fri, 8 May 2020 21:51:30 +0200 Message-ID: <20200508195129.GA19740@lst.de> References: <20200508192009.15302-1-rcampbell@nvidia.com> <20200508192009.15302-5-rcampbell@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200508192009.15302-5-rcampbell-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ralph Campbell Cc: nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kselftest-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jerome Glisse , John Hubbard , Christoph Hellwig , Jason Gunthorpe , Ben Skeggs , Andrew Morton , Shuah Khan , willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org List-Id: nouveau.vger.kernel.org On Fri, May 08, 2020 at 12:20:07PM -0700, Ralph Campbell wrote: > hmm_range_fault() returns an array of page frame numbers and flags for > how the pages are mapped in the requested process' page tables. The PFN > can be used to get the struct page with hmm_pfn_to_page() and the page size > order can be determined with compound_order(page) but if the page is larger > than order 0 (PAGE_SIZE), there is no indication that the page is mapped > using a larger page size. To be fully general, hmm_range_fault() would need > to return the mapping size to handle cases like a 1GB compound page being > mapped with 2MB PMD entries. However, the most common case is the mapping > size the same as the underlying compound page size. > Add a new output flag to indicate this so that callers know it is safe to > use a large device page table mapping if one is available. Why do you need the flag? The caller should be able to just use page_size() (or willys new thp_size helper).