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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 3E4D6C388F2 for ; Fri, 6 Nov 2020 10:28:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3C4121707 for ; Fri, 6 Nov 2020 10:28:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="bzj83Mf9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726692AbgKFK2N (ORCPT ); Fri, 6 Nov 2020 05:28:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727037AbgKFK2M (ORCPT ); Fri, 6 Nov 2020 05:28:12 -0500 Received: from mail-oi1-x243.google.com (mail-oi1-x243.google.com [IPv6:2607:f8b0:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 455D8C0613D3 for ; Fri, 6 Nov 2020 02:28:11 -0800 (PST) Received: by mail-oi1-x243.google.com with SMTP id u127so855642oib.6 for ; Fri, 06 Nov 2020 02:28:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GZSvjJXJ5NeS3xeVpOYrkTBUqUJmeylcGC99/vSxMgE=; b=bzj83Mf9zM2hSbE8EWsBjDPrQihAyugYzXs6/XtzMk42mlteKogf38yikrIVtP0YIp 1PpqGJ83G8CMqUOSy0c+3J2x07vzzrc1y+f0AiA/gsD366OU8Q4TqDzYqRuPe+cWSz/V V9A5M3N3kUQY2mHkFVy5IQrEsMOk51+osCoGc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GZSvjJXJ5NeS3xeVpOYrkTBUqUJmeylcGC99/vSxMgE=; b=tEO2zNv9hfwBL6J9Rfpm57ziSHeIsJhb7KCuuQTcb+o41wr1cHupObHULdqiBTOekA TETaSNKGA/R3riyokX9AqdhhkZ9vUC9FzHpqogM2/OOacWXNe/Ykx0dG0iCKZ7+pwhh/ 75UPcskQLnwEN102hEptdjzOifN2TBStmS2F897VXHJUYgolTwLIgRT3x5dAzf1pfN6z KFG0gADkHYeRJZv0qnRwji0KVL0sexHMGZudmWE8jnob4QwHh9zsfH5DBBiHyvAEmuH0 rJ9pNsBz3H9EI2ua0DGP/QxFoDYhxSXQzPmrdn7JcJUAsGgij7WXBkqMJQV8u57BOnNz 1P7g== X-Gm-Message-State: AOAM533kBkC9CxSOGDnE4ucZKX9hQkdeMDid0q0S1453DLBoeiQ79cv6 Pmj1bfdbshNsNCMs6VR9iZHzx9RF9Oi8PjIZheWonw== X-Google-Smtp-Source: ABdhPJxaH0jX6R8wLLVMSL6X5ZRgt3aYM2nGlRnlOOpo51kJ5ZLuq1XuS09rdAP7rLsL8i/ky1hkd4FCo7S1HBbLmlY= X-Received: by 2002:aca:b141:: with SMTP id a62mr626467oif.101.1604658490602; Fri, 06 Nov 2020 02:28:10 -0800 (PST) MIME-Version: 1.0 References: <20201104140023.GQ36674@ziepe.ca> <20201104162125.GA13007@infradead.org> <20201104163758.GA17425@infradead.org> <20201104164119.GA18218@infradead.org> <20201104181708.GU36674@ziepe.ca> <20201105092524.GQ401619@phenom.ffwll.local> <20201105124950.GZ36674@ziepe.ca> <7ae3486d-095e-cf4e-6b0f-339d99709996@nvidia.com> In-Reply-To: From: Daniel Vetter Date: Fri, 6 Nov 2020 11:27:59 +0100 Message-ID: Subject: Re: [PATCH v5 05/15] mm/frame-vector: Use FOLL_LONGTERM To: John Hubbard , Thomas Hellstrom Cc: Jason Gunthorpe , Christoph Hellwig , "J??r??me Glisse" , linux-samsung-soc , Jan Kara , Pawel Osciak , KVM list , Mauro Carvalho Chehab , LKML , DRI Development , Tomasz Figa , Linux MM , Kyungmin Park , Daniel Vetter , Andrew Morton , Marek Szyprowski , Dan Williams , Linux ARM , "open list:DMA BUFFER SHARING FRAMEWORK" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On Fri, Nov 6, 2020 at 11:01 AM Daniel Vetter wrote: > > On Fri, Nov 6, 2020 at 5:08 AM John Hubbard wrote: > > > > On 11/5/20 4:49 AM, Jason Gunthorpe wrote: > > > On Thu, Nov 05, 2020 at 10:25:24AM +0100, Daniel Vetter wrote: > > >>> /* > > >>> * If we can't determine whether or not a pte is special, then fail immediately > > >>> * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not > > >>> * to be special. > > >>> * > > >>> * For a futex to be placed on a THP tail page, get_futex_key requires a > > >>> * get_user_pages_fast_only implementation that can pin pages. Thus it's still > > >>> * useful to have gup_huge_pmd even if we can't operate on ptes. > > >>> */ > > >> > > >> We support hugepage faults in gpu drivers since recently, and I'm not > > >> seeing a pud_mkhugespecial anywhere. So not sure this works, but probably > > >> just me missing something again. > > > > > > It means ioremap can't create an IO page PUD, it has to be broken up. > > > > > > Does ioremap even create anything larger than PTEs? > > gpu drivers also tend to use vmf_insert_pfn* directly, so we can do > on-demand paging and move buffers around. From what I glanced for > lowest level we to the pte_mkspecial correctly (I think I convinced > myself that vm_insert_pfn does that), but for pud/pmd levels it seems > just yolo. So I dug around a bit more and ttm sets PFN_DEV | PFN_MAP to get past the various pft_t_devmap checks (see e.g. vmf_insert_pfn_pmd_prot()). x86-64 has ARCH_HAS_PTE_DEVMAP, and gup.c seems to handle these specially, but frankly I got totally lost in what this does. The comment above the pfn_t_devmap check makes me wonder whether doing this is correct or not. Also adding Thomas Hellstrom, who implemented the huge map support in ttm. -Daniel > remap_pfn_range seems to indeed split down to pte level always. > > > From my reading, yes. See ioremap_try_huge_pmd(). > > The ioremap here shouldn't matter, since this is for kernel-internal > mappings. So that's all fine I think. > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch