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[209.132.180.67]) by mx.google.com with ESMTP id ce19si318757plb.13.2018.12.20.21.47.58; Thu, 20 Dec 2018 21:48:13 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@ffwll.ch header.s=google header.b=T6pg698U; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389251AbeLTSf2 (ORCPT + 99 others); Thu, 20 Dec 2018 13:35:28 -0500 Received: from mail-it1-f196.google.com ([209.85.166.196]:56081 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725355AbeLTSf1 (ORCPT ); Thu, 20 Dec 2018 13:35:27 -0500 Received: by mail-it1-f196.google.com with SMTP id m62so3438992ith.5 for ; Thu, 20 Dec 2018 10:35:27 -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=LtumSwBzP2k2ql4LvJowB4lWSEg8+PLtrSCsqa/4qIg=; b=T6pg698UH0hUr4kZRSAnuMETvkzpYmQ1zzdoKn/KwTGUkR+3CU6gZ5FGdS4enf+X0W Y4qbxehoVIOqGrNyBhhZml9KOd5HG1IHKJQv8HK5NpUlTiga83EHflauZW4FssxPB4aB GjalL+pGXMSCBogvPapQgH0ygBJO8v9wW7kOU= 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=LtumSwBzP2k2ql4LvJowB4lWSEg8+PLtrSCsqa/4qIg=; b=UxeWf8JD2bh+Jf0StsqGdqAFLRNIBvqz4Y7AV0oGGNnqexecjvwcQSfDISkUbqvHUx ZBle07M+1zfeurJ9RcWqjWnyPEPYSQUzD12aSrZN/+9xP8j4ciq020Mn47tCQeh3owrt zIbHt/P6slMg0NsGJGqmAAGcvqKqmXOtJQL7HbUpl7UcSYjOpwENuYvwX9HO8kNTLUJl +EXkZxi4/2INFMrS29fWtH09asmK7tCg5kRJPDdJccnjBv9YkKm8h4Se18v3HX/6ZgD5 WQmyxXP94zLNNC2y8027s5vKRR1eP1i51fs009jrmFdWvpBt2dnwNPBPGDDuvjwrf5SL xfwg== X-Gm-Message-State: AA+aEWaMVJ9UPikNZlpQlwHNP6SSKmy8zvxDQqMZlfJy+PkRpnufLPl8 3pC25qcoduaanD1MjFVLyt3FhHDzLhtkzBy7PXceFg== X-Received: by 2002:a05:660c:344:: with SMTP id b4mr10575456itl.51.1545330926649; Thu, 20 Dec 2018 10:35:26 -0800 (PST) MIME-Version: 1.0 References: <20181127103252.20994-1-andr2000@gmail.com> <17640791-5306-f7e4-8588-dd39c14e975b@tronnes.org> <20181220153646.GA22997@infradead.org> <20181220173950.GA19641@infradead.org> <20181220183311.GA30801@infradead.org> In-Reply-To: <20181220183311.GA30801@infradead.org> From: Daniel Vetter Date: Thu, 20 Dec 2018 19:35:15 +0100 Message-ID: Subject: Re: [PATCH] drm/xen-front: Make shmem backed display buffer coherent To: Christoph Hellwig Cc: Oleksandr Andrushchenko , Juergen Gross , Oleksandr Andrushchenko , Linux Kernel Mailing List , dri-devel , Daniel Vetter , xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 20, 2018 at 7:33 PM Christoph Hellwig wrote: > > On Thu, Dec 20, 2018 at 07:29:37PM +0100, Daniel Vetter wrote: > > What we most definitely not want to end up with though is actually > > streaming dma, because with that all the zero copy buffer sharing > > tricks become pointless. There's pretty epic amounts of hacks to work > > around this, I have no idea what's supposed to give here. > > Err, with streaming DMA buffer sharing is trivial. The coherent DMA > allocator is what causes all kinds of horrible hacks that can't actually > work on various platforms. Hm, I thought the streaming dma api is the one that causes bounce buffers and all that fun. If you're unlucky at least. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch