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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D3DEC00140 for ; Wed, 10 Aug 2022 19:26:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231978AbiHJT0X (ORCPT ); Wed, 10 Aug 2022 15:26:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231214AbiHJT0Q (ORCPT ); Wed, 10 Aug 2022 15:26:16 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A8BF6A492; Wed, 10 Aug 2022 12:26:15 -0700 (PDT) Received: from [192.168.2.145] (109-252-119-13.nat.spd-mgts.ru [109.252.119.13]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id F1FD86601C73; Wed, 10 Aug 2022 20:26:12 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1660159574; bh=lKDS+8XGWYTEUMy9n4JVlMo+97ehb8hPjoaSdgmoHsI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Ca0mCEqTwate7hBwX9o+nUz8JpwDmjo7nQv6ySUjKW4CuE+Dqzg/nDRpy81WSU6M5 Qw2/brgHxEM0B+o02EXi9Oc+za8LOWC/FRPkNpwDs/kuw4cSemcG9/JeKb5qwDQ5+U Fu3nRb90Vr2zl75fQ20Q9xbpueW701PD5qYzncovk4c469mTYTKp8FWnTf9hSRboIR LXmoYbtLP3KEO6vY1cWhbl48eVmbdI1srieFfshO9SzFs2votZ8WJUk8/s1abNXikv 7jsTeKWR5qg9FcQh+h6fbIo5yFFZQpBrMlCPdHGZMKsx0QYtuikd2lOguvkgz6rkO0 uY+tlcbpmfQmw== Message-ID: <9674d00e-c0d6-ceba-feab-5dc475bda694@collabora.com> Date: Wed, 10 Aug 2022 22:26:11 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH v8 2/2] drm/gem: Don't map imported GEMs Content-Language: en-US To: Rob Clark , =?UTF-8?Q?Christian_K=c3=b6nig?= , David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Emil Velikov , =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= , Linux Kernel Mailing List , dri-devel , "open list:VIRTIO GPU DRIVER" , linux-tegra@vger.kernel.org, Dmitry Osipenko , kernel@collabora.com Cc: Daniel Vetter References: <20220701090240.1896131-1-dmitry.osipenko@collabora.com> <20220701090240.1896131-3-dmitry.osipenko@collabora.com> <2bb95e80-b60a-36c0-76c8-a06833032c77@amd.com> <2a646ce4-c2ec-3b11-77a0-cc720afd6fe1@collabora.com> From: Dmitry Osipenko In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/10/22 18:08, Rob Clark wrote: > On Wed, Aug 10, 2022 at 4:47 AM Daniel Vetter wrote: >> >> On Wed, Jul 06, 2022 at 10:02:07AM +0300, Dmitry Osipenko wrote: >>> On 7/6/22 00:48, Rob Clark wrote: >>>> On Tue, Jul 5, 2022 at 4:51 AM Christian König wrote: >>>>> >>>>> Am 01.07.22 um 11:02 schrieb Dmitry Osipenko: >>>>>> Drivers that use drm_gem_mmap() and drm_gem_mmap_obj() helpers don't >>>>>> handle imported dma-bufs properly, which results in mapping of something >>>>>> else than the imported dma-buf. On NVIDIA Tegra we get a hard lockup when >>>>>> userspace writes to the memory mapping of a dma-buf that was imported into >>>>>> Tegra's DRM GEM. >>>>>> >>>>>> Majority of DRM drivers prohibit mapping of the imported GEM objects. >>>>>> Mapping of imported GEMs require special care from userspace since it >>>>>> should sync dma-buf because mapping coherency of the exporter device may >>>>>> not match the DRM device. Let's prohibit the mapping for all DRM drivers >>>>>> for consistency. >>>>>> >>>>>> Suggested-by: Thomas Hellström >>>>>> Signed-off-by: Dmitry Osipenko >>>>> >>>>> I'm pretty sure that this is the right approach, but it's certainly more >>>>> than possible that somebody abused this already. >>>> >>>> I suspect that this is abused if you run deqp cts on android.. ie. all >>>> winsys buffers are dma-buf imports from gralloc. And then when you >>>> hit readpix... >>>> >>>> You might only hit this in scenarios with separate gpu and display (or >>>> dGPU+iGPU) because self-imports are handled differently in >>>> drm_gem_prime_import_dev().. and maybe not in cases where you end up >>>> with a blit from tiled/compressed to linear.. maybe that narrows the >>>> scope enough to just fix it in userspace? >>> >>> Given that that only drivers which use DRM-SHMEM potentially could've >>> map imported dma-bufs (Panfrost, Lima) and they already don't allow to >>> do that, I think we're good. >> >> So can I have an ack from Rob here or are there still questions that this >> might go boom? >> >> Dmitry, since you have a bunch of patches merged now I think would also be >> good to get commit rights so you can drive this more yourself. I've asked >> Daniel Stone to help you out with getting that. > > I *think* we'd be ok with this on msm, mostly just by dumb luck. > Because the dma-buf's we import will be self-import. I'm less sure > about panfrost (src/panfrost/lib/pan_bo.c doesn't seem to have a > special path for imported dma-bufs either, and in that case they won't > be self-imports.. but I guess no one has tried to run android cts on > panfrost). The last time I tried to mmap dma-buf imported to Panfrost didn't work because Panfrost didn't implement something needed for that. I'll need to take a look again because can't recall what it was. > What about something less drastic to start, like (apologies for > hand-edited patch): > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index 86d670c71286..fc9ec42fa0ab 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -1034,6 +1034,10 @@ int drm_gem_mmap_obj(struct drm_gem_object > *obj, unsigned long obj_size, > { > int ret; > > + WARN_ON_ONCE(obj->import_attach); This will hang NVIDIA Tegra, which is what this patch fixed initially. If neither of upstream DRM drivers need to map imported dma-bufs and never needed, then why do we need this? -- Best regards, Dmitry