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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 197C8C433E2 for ; Wed, 9 Sep 2020 17:12:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B67C921919 for ; Wed, 9 Sep 2020 17:12:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="BztXimA7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731281AbgIIRM3 (ORCPT ); Wed, 9 Sep 2020 13:12:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730287AbgIIPcg (ORCPT ); Wed, 9 Sep 2020 11:32:36 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1CDCC06123A; Wed, 9 Sep 2020 08:00:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=MVAeHe5FDtxLkhCRtWl5/1qAQHWmRELNofFvInrKy68=; b=BztXimA7lzcj8i0a7Hfb2iCsRV 8Jbc1EgSgRrX823PDBzAnIPcQVx1llIRGOg31njOV1ZiixejTgKPCIhqyh0B3oBbBpMbZyUaKkipa d4wtX8Tb7QBsK4SVuh/xnFcyvlxnCr+IByHYj0nmLwfWMfGltfZbuzMnMWoJeOLvLdSKJ+UMBXkA0 AYMCECsJvVfCxvGEGhvsd0I849jKePnGGTbkI4Rwm/zWQNSCbCnBDFhthuvRhbgd4wdm8mwYwkLpO SyGu2Y7hhxmqb35g1sqzEm9EVWr3ddpLrMPlUOkGm4u0F1TiB2CThO7OMYC3vv78PrfGZDG1i91d4 tR/q5t7w==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kG1a3-0007u9-24; Wed, 09 Sep 2020 15:00:15 +0000 Date: Wed, 9 Sep 2020 16:00:15 +0100 From: Matthew Wilcox To: Christoph Hellwig Cc: Jason Gunthorpe , Ming Mao , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, alex.williamson@redhat.com, akpm@linux-foundation.org, cohuck@redhat.com, jianjay.zhou@huawei.com, weidong.huang@huawei.com, peterx@redhat.com, aarcange@redhat.com, wangyunjian@huawei.com, jhubbard@nvidia.com Subject: Re: [PATCH V4 1/2] vfio dma_map/unmap: optimized for hugetlbfs pages Message-ID: <20200909150015.GI6583@casper.infradead.org> References: <20200908133204.1338-1-maoming.maoming@huawei.com> <20200908133204.1338-2-maoming.maoming@huawei.com> <20200909080114.GA8321@infradead.org> <20200909130518.GE87483@ziepe.ca> <20200909142941.GA23553@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200909142941.GA23553@infradead.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 09, 2020 at 03:29:41PM +0100, Christoph Hellwig wrote: > On Wed, Sep 09, 2020 at 10:05:18AM -0300, Jason Gunthorpe wrote: > > How to use? The VMAs can have mixed page sizes so the caller would > > have to somehow switch and call twice? Not sure this is faster. > > We can find out the page size based on the page. Right now it is > rather cumbersome, but one of willys pending series has a nicer helper > for that. Actually already merged. There's page_size() which went into 5.4, and is the one you'd want to use (also page_shift() and compound_nr()). The thp_* equivalents (merged in 5.9) compile away to nothing if you don't have CONFIG_TRANSPARENT_HUGEPAGE enabled, but since there are many ways of getting a compound page mapped into userspace, page_size() is the helper to use for VFIO.