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=-3.9 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 F29EDC433E2 for ; Thu, 17 Sep 2020 17:24:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF36E221E3 for ; Thu, 17 Sep 2020 17:24:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="Oe+9XFyi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726419AbgIQRXs (ORCPT ); Thu, 17 Sep 2020 13:23:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726390AbgIQRXX (ORCPT ); Thu, 17 Sep 2020 13:23:23 -0400 Received: from mail-oi1-x242.google.com (mail-oi1-x242.google.com [IPv6:2607:f8b0:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C94B0C061756 for ; Thu, 17 Sep 2020 10:23:14 -0700 (PDT) Received: by mail-oi1-x242.google.com with SMTP id z26so3309697oih.12 for ; Thu, 17 Sep 2020 10:23:14 -0700 (PDT) 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:content-transfer-encoding; bh=F86p0ud99YSiTMCN0ZfJJse9lFQfi+WRyzF06l3LfwA=; b=Oe+9XFyi4XwSdp0c08MIQlmhrPw1Z8ltKB2S7V3IMBblrL34HKoK0b4blCy3ZHSJxj 7IaJJ0RwaRrjJztcw/95TWgK1iToMprnqvda3Cw5Rs+2ciTDAeh8nMCt44s2ulVhn6KN 6sAVjFYZRVuJFjONKZdpeD53O77tF58gs1uyI= 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:content-transfer-encoding; bh=F86p0ud99YSiTMCN0ZfJJse9lFQfi+WRyzF06l3LfwA=; b=iYvHEOo+NPuNfKMDZGAcPIAGtQPBEx9qMVG7jju+i3ZAYZEmi+aKZiot3hpKSqnY85 61+v2EJLAJ3kcXPA5e1VFSuEruUmtouPRb/ksJrY3GQpjGweVQJlwhbrRU7GIw5p++ql PmDMSRJ8KsivnnFyKPqH4DPv/hgvvr35l8YPYPS7sR8nNw0vbjHhp7DGdJ9XZmRT0D6n BxkzEwSavr5bvCh1tjfIH9Y8QoWYcq6Utq3W8XUbVUZsdkDEIXYLGXiIrzKzZrGhhF7u LWwowbv2QXKKEym0pdaVRjGS06rbKaDFu9cxy1Bo7hh4V/9KHbmvnAt+oTQILF96lnPk DheQ== X-Gm-Message-State: AOAM532a0Qw0u8K5N07B8FK3inHbRu9Uuai+J3LadnjJxVRGR14GLtj7 kpubuoP5QDk/ZvuKmyQ0PcPp4+SXQj3NzFd5Z0oKwQ== X-Google-Smtp-Source: ABdhPJwF3dNmQNnc08BdxH8My7DtOBpKWMR10LzO7dt3VFCMGmJE1UwcTFFGHLsdQ5ho5h5wrPc5sUf6w5ZuU6y8//k= X-Received: by 2002:aca:6083:: with SMTP id u125mr7050119oib.14.1600363394219; Thu, 17 Sep 2020 10:23:14 -0700 (PDT) MIME-Version: 1.0 References: <20200917113110.GE8409@ziepe.ca> <6fd74b84-959c-8b3b-c27b-e9fbf66396c7@gmail.com> <20200917121858.GF8409@ziepe.ca> <20200917143551.GG8409@ziepe.ca> <5b330920-c789-fac7-e9b1-49f3bc1097a8@gmail.com> <20200917152456.GH8409@ziepe.ca> <20200917163907.GI8409@ziepe.ca> In-Reply-To: <20200917163907.GI8409@ziepe.ca> From: Daniel Vetter Date: Thu, 17 Sep 2020 19:23:03 +0200 Message-ID: Subject: Re: [Linaro-mm-sig] Changing vma->vm_file in dma_buf_mmap() To: Jason Gunthorpe Cc: =?UTF-8?Q?Christian_K=C3=B6nig?= , Linux Kernel Mailing List , dri-devel , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Linux MM , Andrew Morton , "open list:DMA BUFFER SHARING FRAMEWORK" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 17, 2020 at 6:39 PM Jason Gunthorpe wrote: > > On Thu, Sep 17, 2020 at 06:06:14PM +0200, Christian K=C3=B6nig wrote: > > > > If it is already taking a page fault I'm not sure the extra functio= n > > > > call indirection is going to be a big deal. Having a uniform VMA > > > > sounds saner than every driver custom rolling something. > > > > > > > > When I unwound a similar mess in RDMA all the custom VMA stuff in t= he > > > > drivers turned out to be generally buggy, at least. > > > > > > > > Is vma->vm_file->private_data universally a dma_buf pointer at leas= t? > > > Nope. I think if you want this without some large scale rewrite of a > > > lot of code we'd need a vmops->get_dmabuf or similar. Not pretty, but > > > would get the job done. > > > > Yeah, agree that sounds like the simplest approach. > > I don't think that will fly, it is clearly only papering over a mess > inside DRM/dma buf :\ dma-buf started out as something to paper over the disjoint mess of allocators, since it was pretty clear to anyone involved we're not going to unify them anytime soon, if ever. So the mess pretty much is bound to stay. I think most reasonable thing would be to throw a common vmops in there somehow, but even that means some large scale surgery across every driver/subsystem involved in dma-buf. It wouldn't unify anything, all it would give you is a constant vma->vm_ops to do some kind of upcasting. And that would still only give you a slightly less opaque pointer with a callback to upcast to a dma-buf in some driver/subsystem specific way. -Daniel --=20 Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch 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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 D82FBC43461 for ; Thu, 17 Sep 2020 17:23:17 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0DDA0221EC for ; Thu, 17 Sep 2020 17:23:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="Oe+9XFyi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0DDA0221EC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0F24689173; Thu, 17 Sep 2020 17:23:16 +0000 (UTC) Received: from mail-oi1-x241.google.com (mail-oi1-x241.google.com [IPv6:2607:f8b0:4864:20::241]) by gabe.freedesktop.org (Postfix) with ESMTPS id E356989173 for ; Thu, 17 Sep 2020 17:23:14 +0000 (UTC) Received: by mail-oi1-x241.google.com with SMTP id w16so3371360oia.2 for ; Thu, 17 Sep 2020 10:23:14 -0700 (PDT) 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:content-transfer-encoding; bh=F86p0ud99YSiTMCN0ZfJJse9lFQfi+WRyzF06l3LfwA=; b=Oe+9XFyi4XwSdp0c08MIQlmhrPw1Z8ltKB2S7V3IMBblrL34HKoK0b4blCy3ZHSJxj 7IaJJ0RwaRrjJztcw/95TWgK1iToMprnqvda3Cw5Rs+2ciTDAeh8nMCt44s2ulVhn6KN 6sAVjFYZRVuJFjONKZdpeD53O77tF58gs1uyI= 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:content-transfer-encoding; bh=F86p0ud99YSiTMCN0ZfJJse9lFQfi+WRyzF06l3LfwA=; b=RsvxR4LhHo+27ryWYQDEoQEqqH0KAJi0FVVErxEca05qTbEb2P6pppvC7SBERG2pHw WFyT1II9V4jyjVJNUNo4zMg77NpvpNc9XBP0JfCPFL1abfwqFZbySzkWPDk9Jja7VpUo vZNS/zgNTyidmcLPO2sxj6xI2pz0CFvabQii7fj+x6y1NIKtiTOhY1H/jc19B1fvPKm+ nKmSUOiujbgqTj8aVhcGiOC/DOUSUmlrUkoGr58H4y9an1I9lu5C/UIhRBw74ksySEax xWV2xJVEm0bcz66gqxnOdfOHtcV4J6q6QSmXbIYS5E8IFy7+83MGUieHHw45YBhGGDEZ 53og== X-Gm-Message-State: AOAM5314fzHAfkXs2Dz1Q8g/6Rd3O+bJET5c8J040EHZ2m8AbBtg3qJg IQNtNUOTZNHVpQw3tqEjT3Y12F0e7rFOFPxYZL+new== X-Google-Smtp-Source: ABdhPJwF3dNmQNnc08BdxH8My7DtOBpKWMR10LzO7dt3VFCMGmJE1UwcTFFGHLsdQ5ho5h5wrPc5sUf6w5ZuU6y8//k= X-Received: by 2002:aca:6083:: with SMTP id u125mr7050119oib.14.1600363394219; Thu, 17 Sep 2020 10:23:14 -0700 (PDT) MIME-Version: 1.0 References: <20200917113110.GE8409@ziepe.ca> <6fd74b84-959c-8b3b-c27b-e9fbf66396c7@gmail.com> <20200917121858.GF8409@ziepe.ca> <20200917143551.GG8409@ziepe.ca> <5b330920-c789-fac7-e9b1-49f3bc1097a8@gmail.com> <20200917152456.GH8409@ziepe.ca> <20200917163907.GI8409@ziepe.ca> In-Reply-To: <20200917163907.GI8409@ziepe.ca> From: Daniel Vetter Date: Thu, 17 Sep 2020 19:23:03 +0200 Message-ID: Subject: Re: [Linaro-mm-sig] Changing vma->vm_file in dma_buf_mmap() To: Jason Gunthorpe X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux Kernel Mailing List , dri-devel , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Linux MM , Andrew Morton , =?UTF-8?Q?Christian_K=C3=B6nig?= , "open list:DMA BUFFER SHARING FRAMEWORK" Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" T24gVGh1LCBTZXAgMTcsIDIwMjAgYXQgNjozOSBQTSBKYXNvbiBHdW50aG9ycGUgPGpnZ0B6aWVw ZS5jYT4gd3JvdGU6Cj4KPiBPbiBUaHUsIFNlcCAxNywgMjAyMCBhdCAwNjowNjoxNFBNICswMjAw LCBDaHJpc3RpYW4gS8O2bmlnIHdyb3RlOgo+ID4gPiA+IElmIGl0IGlzIGFscmVhZHkgdGFraW5n IGEgcGFnZSBmYXVsdCBJJ20gbm90IHN1cmUgdGhlIGV4dHJhIGZ1bmN0aW9uCj4gPiA+ID4gY2Fs bCBpbmRpcmVjdGlvbiBpcyBnb2luZyB0byBiZSBhIGJpZyBkZWFsLiBIYXZpbmcgYSB1bmlmb3Jt IFZNQQo+ID4gPiA+IHNvdW5kcyBzYW5lciB0aGFuIGV2ZXJ5IGRyaXZlciBjdXN0b20gcm9sbGlu ZyBzb21ldGhpbmcuCj4gPiA+ID4KPiA+ID4gPiBXaGVuIEkgdW53b3VuZCBhIHNpbWlsYXIgbWVz cyBpbiBSRE1BIGFsbCB0aGUgY3VzdG9tIFZNQSBzdHVmZiBpbiB0aGUKPiA+ID4gPiBkcml2ZXJz IHR1cm5lZCBvdXQgdG8gYmUgZ2VuZXJhbGx5IGJ1Z2d5LCBhdCBsZWFzdC4KPiA+ID4gPgo+ID4g PiA+IElzIHZtYS0+dm1fZmlsZS0+cHJpdmF0ZV9kYXRhIHVuaXZlcnNhbGx5IGEgZG1hX2J1ZiBw b2ludGVyIGF0IGxlYXN0Pwo+ID4gPiBOb3BlLiBJIHRoaW5rIGlmIHlvdSB3YW50IHRoaXMgd2l0 aG91dCBzb21lIGxhcmdlIHNjYWxlIHJld3JpdGUgb2YgYQo+ID4gPiBsb3Qgb2YgY29kZSB3ZSdk IG5lZWQgYSB2bW9wcy0+Z2V0X2RtYWJ1ZiBvciBzaW1pbGFyLiBOb3QgcHJldHR5LCBidXQKPiA+ ID4gd291bGQgZ2V0IHRoZSBqb2IgZG9uZS4KPiA+Cj4gPiBZZWFoLCBhZ3JlZSB0aGF0IHNvdW5k cyBsaWtlIHRoZSBzaW1wbGVzdCBhcHByb2FjaC4KPgo+IEkgZG9uJ3QgdGhpbmsgdGhhdCB3aWxs IGZseSwgaXQgaXMgY2xlYXJseSBvbmx5IHBhcGVyaW5nIG92ZXIgYSBtZXNzCj4gaW5zaWRlIERS TS9kbWEgYnVmIDpcCgpkbWEtYnVmIHN0YXJ0ZWQgb3V0IGFzIHNvbWV0aGluZyB0byBwYXBlciBv dmVyIHRoZSBkaXNqb2ludCBtZXNzIG9mCmFsbG9jYXRvcnMsIHNpbmNlIGl0IHdhcyBwcmV0dHkg Y2xlYXIgdG8gYW55b25lIGludm9sdmVkIHdlJ3JlIG5vdApnb2luZyB0byB1bmlmeSB0aGVtIGFu eXRpbWUgc29vbiwgaWYgZXZlci4gU28gdGhlIG1lc3MgcHJldHR5IG11Y2ggaXMKYm91bmQgdG8g c3RheS4KCkkgdGhpbmsgbW9zdCByZWFzb25hYmxlIHRoaW5nIHdvdWxkIGJlIHRvIHRocm93IGEg Y29tbW9uIHZtb3BzIGluCnRoZXJlIHNvbWVob3csIGJ1dCBldmVuIHRoYXQgbWVhbnMgc29tZSBs YXJnZSBzY2FsZSBzdXJnZXJ5IGFjcm9zcwpldmVyeSBkcml2ZXIvc3Vic3lzdGVtIGludm9sdmVk IGluIGRtYS1idWYuIEl0IHdvdWxkbid0IHVuaWZ5CmFueXRoaW5nLCBhbGwgaXQgd291bGQgZ2l2 ZSB5b3UgaXMgYSBjb25zdGFudCB2bWEtPnZtX29wcyB0byBkbyBzb21lCmtpbmQgb2YgdXBjYXN0 aW5nLiBBbmQgdGhhdCB3b3VsZCBzdGlsbCBvbmx5IGdpdmUgeW91IGEgc2xpZ2h0bHkgbGVzcwpv cGFxdWUgcG9pbnRlciB3aXRoIGEgY2FsbGJhY2sgdG8gdXBjYXN0IHRvIGEgZG1hLWJ1ZiBpbiBz b21lCmRyaXZlci9zdWJzeXN0ZW0gc3BlY2lmaWMgd2F5LgotRGFuaWVsCi0tIApEYW5pZWwgVmV0 dGVyClNvZnR3YXJlIEVuZ2luZWVyLCBJbnRlbCBDb3Jwb3JhdGlvbgpodHRwOi8vYmxvZy5mZnds bC5jaApfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpkcmkt ZGV2ZWwgbWFpbGluZyBsaXN0CmRyaS1kZXZlbEBsaXN0cy5mcmVlZGVza3RvcC5vcmcKaHR0cHM6 Ly9saXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9kcmktZGV2ZWwK