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 82D49C433E1 for ; Thu, 14 May 2020 11:39:11 +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 5A7642074A for ; Thu, 14 May 2020 11:39:11 +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="q8byuDEV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5A7642074A 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 140BF6E32B; Thu, 14 May 2020 11:39:08 +0000 (UTC) Received: from mail-oo1-xc41.google.com (mail-oo1-xc41.google.com [IPv6:2607:f8b0:4864:20::c41]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2D1776E180; Thu, 14 May 2020 11:39:05 +0000 (UTC) Received: by mail-oo1-xc41.google.com with SMTP id z26so282306oog.8; Thu, 14 May 2020 04:39:05 -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=ZSwtCexk9nrc5wXHZb6xl7x3Ukus0pVklq+X0lXtP9M=; b=q8byuDEV/HBaHutEfKPBCsOyJyKXLTe4fdppUu5YAyVeuJZ/cfy0kQWEcbAeRjIVy6 AZkToLQ6x/5AVr9U+gRwDb9fIvkuXhFu+VIWabcrx71puBIQSHn8hH7/T08WuZAGb2B7 Yn2cYkz3VxMdDJbOOAyk7jH906xTaQoGoFsaxjiRg+KFqP1wIS1AldxFzTqZs2TIC8F3 HdlclyNH5C5/2cRr3L16eW33oGDt2+ZZuwoot7brtKW68FMdUhy5Vm/2oO1mPQ2NKV8s yuUbUGhQxHy2Dmp+DUlMBgnV8IwEZIzwfAfefoJkjWWveDDJSK548DuLRV7v6Pqr5Zw0 Rb2Q== 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=ZSwtCexk9nrc5wXHZb6xl7x3Ukus0pVklq+X0lXtP9M=; b=Qj07GzRDmOLBPGO8r4Saf5UBrHkhEpO57pPNmWLkf/CO5tueYFR6VaXJtWXjDO/6yb 5SaANoatNOWTHbjQG4V3WahPicGe6k669PbHvKliQsIe3Xj2b99xqTMTV7j25E5MvQXX +XqJQQFLvG2FhxZabVhnrsoKksDBI6BM5jgLhWHJ93gvycz6BPZ9T5Fq5pUQ/yTc3aFF xbGh5cexZmaDcqn8vfq+/706aKn9U28l6WoKtY6mIsTI2nOIDwqyJ//mIY1SyzCrNgzI NG35azU99FzckG9Jxx3gVutw71NEZr2xXKmoZ+dyu/zxeej31yPKZxV94T/PO2yyXRzr a+eg== X-Gm-Message-State: AOAM531Zn6v5ouruNaurBpPwZku01Xa6vNoPdOlW64Ro0oOV/zqTTcFh zR7kH9s+BkBoMyq1uEHHlePmSuAU9z+DOVmKbM4= X-Google-Smtp-Source: ABdhPJzpF/j77VZ1mUAB6oImvLDs5y+yw8Ffqf9KnZIjayJc7xQ/fTQmYbxSeR6K0/KuM1T7We9orB4e+Fb4bfMi4ag= X-Received: by 2002:a4a:a50e:: with SMTP id v14mr3145833ook.27.1589456345130; Thu, 14 May 2020 04:39:05 -0700 (PDT) MIME-Version: 1.0 References: <20200511091142.208787-1-daniel.vetter@ffwll.ch> <20200511091142.208787-3-daniel.vetter@ffwll.ch> In-Reply-To: From: Oded Gabbay Date: Thu, 14 May 2020 14:38:38 +0300 Message-ID: To: Daniel Vetter 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: 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" 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. Thanks, Oded > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx