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=-0.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 3BE41C433DF for ; Wed, 20 May 2020 18:10:14 +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 F2B9920671 for ; Wed, 20 May 2020 18:10:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dZP/+Ezy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2B9920671 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8798A8932D; Wed, 20 May 2020 18:10:13 +0000 (UTC) Received: from mail-ot1-x343.google.com (mail-ot1-x343.google.com [IPv6:2607:f8b0:4864:20::343]) by gabe.freedesktop.org (Postfix) with ESMTPS id 211EC8932D; Wed, 20 May 2020 18:10:13 +0000 (UTC) Received: by mail-ot1-x343.google.com with SMTP id x22so3273834otq.4; Wed, 20 May 2020 11:10:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=tx9re6lXGFdfxVUAVwva8EahuEz3Z+j2jfuKERIypGA=; b=dZP/+Ezyao2q+g8UeMH7UCWOKPM2rUJz762yFGC8HBceR93568dZwtO5olvMji49Kw hEFJyjeG4dsi9+JmPSTjCeXXKuiqj0hGeAE1EhgcsbqTtFzlb2YXv/Kpftg/fF1kcRi3 rEYiIiO6n0Hjllej82qDcasPEHahE1iPUkKzmdTzhZsddaMzMVqJp/jUsszHB4I9K4wM TnqWaN21p2xUge4/Ie4sNg6PVHtDFnBcO1bVtsdn30YyGe2g5q1Ph5HD0mi3FNrqcHct iwweP+6OfIZsahDggQGT/c92eZhpe1SDn/glDgk9w2BziuLYJPYzqcV2oh2ADOUoUSdZ Izvg== 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=tx9re6lXGFdfxVUAVwva8EahuEz3Z+j2jfuKERIypGA=; b=GN87LLnqzVosvj+gTrQRmFsZjKH+yc/tssfbehjKVF+hceuWUTqZA79NbcIN+gys/N uynfcTAxKzPx0ay4Iplmcc75OubfgSd6trnrpkaWqv/X1R+yHyH0TadvWFiPYlLkZuJn XsO80RtL/IW3HGfrEgpfBf8+HKmZwKzvSrF8Ft5tHaTxd/LdhBzrRVMN8RrYLZb8FkY2 GQE8U6IisonROdtUK1P803CtHjeQKsiGNIleayQYFUkQgLYqIOmq7LcSQWTjPdeTBoLi D5WsENp2oxtPDTCwf24tzTJXvZRi5OUm53YS/laRM12EwPVj/B3RYVPYa9/5+ssez20C QfRg== X-Gm-Message-State: AOAM533Bs4gZDkOpQauKxwNNWmLIgHkrxoi/VLJ/A4i6tqJ78zuTPLLr 7KNRObyH1fj4p/r4E50a1uLW4yk9o+6JaCOJ1uk= X-Google-Smtp-Source: ABdhPJwoSeRQqKhyxkLlOF1QXnKRkw6Q0I8K11tOPLyQ2ECm09g1/OdzJ2KuQAmdH5Tb6w7Z2yIJxgImrYj8J+weL4M= X-Received: by 2002:a4a:88e4:: with SMTP id q33mr4005168ooh.27.1589998212250; Wed, 20 May 2020 11:10:12 -0700 (PDT) MIME-Version: 1.0 References: <20200511091142.208787-1-daniel.vetter@ffwll.ch> <20200511091142.208787-3-daniel.vetter@ffwll.ch> <20200520180456.GC206103@phenom.ffwll.local> In-Reply-To: <20200520180456.GC206103@phenom.ffwll.local> From: Oded Gabbay Date: Wed, 20 May 2020 21:09:42 +0300 Message-ID: To: Oded Gabbay , Dave Airlie , Greg Kroah-Hartman , Intel Graphics Development , LKML , DRI Development , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Olof Johansson , Daniel Vetter , Sumit Semwal , Linux Media Mailing List Subject: Re: [Intel-gfx] [PATCH 3/3] misc/habalabs: don't set default fence_ops->wait X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, May 20, 2020 at 9:05 PM Daniel Vetter wrote: > > On Thu, May 14, 2020 at 02:38:38PM +0300, Oded Gabbay wrote: > > On Tue, May 12, 2020 at 9:12 AM Daniel Vetter wrote: > > > > > > On Tue, May 12, 2020 at 4:14 AM Dave Airlie wrote: > > > > > > > > On Mon, 11 May 2020 at 19:37, Oded Gabbay wrote: > > > > > > > > > > On Mon, May 11, 2020 at 12:11 PM Daniel Vetter wrote: > > > > > > > > > > > > It's the default. > > > > > Thanks for catching that. > > > > > > > > > > > > > > > > > Also so much for "we're not going to tell the graphics people how to > > > > > > review their code", dma_fence is a pretty core piece of gpu driver > > > > > > infrastructure. And it's very much uapi relevant, including piles of > > > > > > corresponding userspace protocols and libraries for how to pass these > > > > > > around. > > > > > > > > > > > > Would be great if habanalabs would not use this (from a quick look > > > > > > it's not needed at all), since open source the userspace and playing > > > > > > by the usual rules isn't on the table. If that's not possible (because > > > > > > it's actually using the uapi part of dma_fence to interact with gpu > > > > > > drivers) then we have exactly what everyone promised we'd want to > > > > > > avoid. > > > > > > > > > > We don't use the uapi parts, we currently only using the fencing and > > > > > signaling ability of this module inside our kernel code. But maybe I > > > > > didn't understand what you request. You want us *not* to use this > > > > > well-written piece of kernel code because it is only used by graphics > > > > > drivers ? > > > > > I'm sorry but I don't get this argument, if this is indeed what you meant. > > > > > > > > We would rather drivers using a feature that has requirements on > > > > correct userspace implementations of the feature have a userspace that > > > > is open source and auditable. > > > > > > > > Fencing is tricky, cross-device fencing is really tricky, and having > > > > the ability for a closed userspace component to mess up other people's > > > > drivers, think i915 shared with closed habana userspace and shared > > > > fences, decreases ability to debug things. > > > > > > > > Ideally we wouldn't offer users known untested/broken scenarios, so > > > > yes we'd prefer that drivers that intend to expose a userspace fencing > > > > api around dma-fence would adhere to the rules of the gpu drivers. > > > > > > > > I'm not say you have to drop using dma-fence, but if you move towards > > > > cross-device stuff I believe other drivers would be correct in > > > > refusing to interact with fences from here. > > > > > > The flip side is if you only used dma-fence.c "because it's there", > > > and not because it comes with an uapi attached and a cross-driver > > > kernel internal contract for how to interact with gpu drivers, then > > > there's really not much point in using it. It's a custom-rolled > > > wait_queue/event thing, that's all. Without the gpu uapi and gpu > > > cross-driver contract it would be much cleaner to just use wait_queue > > > directly, and that's a construct all kernel developers understand, not > > > just gpu folks. From a quick look at least habanalabs doesn't use any > > > of these uapi/cross-driver/gpu bits. > > > -Daniel > > > > Hi Daniel, > > I want to say explicitly that we don't use the dma-buf uapi parts, nor > > we intend to use them to communicate with any GPU device. We only use > > it as simple completion mechanism as it was convenient to use. > > I do understand I can exchange that mechanism with a simpler one, and > > I will add an internal task to do it (albeit not in a very high > > priority) and upstream it, its just that it is part of our data path > > so we need to thoroughly validate it first. > > Sounds good. > > Wrt merging this patch here, can you include that in one of your next > pulls? Or should I toss it entirely, waiting for you to remove dma_fence > outright? I'll include it in the next pull. Thanks, Oded > > Thanks, Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx