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 772F2C25B0E for ; Fri, 12 Aug 2022 14:57:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232828AbiHLO52 (ORCPT ); Fri, 12 Aug 2022 10:57:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232085AbiHLO5Z (ORCPT ); Fri, 12 Aug 2022 10:57:25 -0400 Received: from mail-io1-xd32.google.com (mail-io1-xd32.google.com [IPv6:2607:f8b0:4864:20::d32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38A7F9C210; Fri, 12 Aug 2022 07:57:24 -0700 (PDT) Received: by mail-io1-xd32.google.com with SMTP id v185so980143ioe.11; Fri, 12 Aug 2022 07:57:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc; bh=zKjSj2wTsw/rznrfDfUfY+1E6AA9/o4ZtfsJOOVevII=; b=I0hYDAQhR6fZiGQJpTRTzwuIV7C2zNpXtIo1w4Znh1k2YeTNw1apiK2zkUfv0NrswJ ImnfizLL+jBzIUA5S0nSjhWI4mIrInUl1pNo+cjA5XFipGL4B6nuWTz7H1eOrAOmDflJ IU93NK5XEK9vuM2SNjqmgQkXjbLECjKFk2d5dUv8YcT53dCZwbxnNG+AOuDJFmfEtOTO cXC7PknC37U43S2F1oYjlHyXfVdcTCiZy3guMRpK+lg2maL2K6yeLwmZMgEP1gQiNWDB dwS+EnmM0RNc5h4b8vAvGb4l7OXFr3WgZo8Arje190utWbbH4kKqo9XmybzOABmSPH0M euwA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc; bh=zKjSj2wTsw/rznrfDfUfY+1E6AA9/o4ZtfsJOOVevII=; b=b7QP2WjSuT2S3bW9L2rKX8qKYzFK51PnhBk/+pQ8ZqKZy23vL27NmNtYZ/JcJOfuew C4QIV4lOLTyIr/5FWwoue8MjFzY63dNUE2LN3WFl6epg0m9GN+B/l/yhjo8hvMJV+3XI GFcUPd9iTlwPPZt3MA6OofOFDpViDLFEDe3dNAp4Ks+mG+sc8mfKs2EK4zltn5jCJwNg 6NVs/FLe/67fnZzN3mhwse85SW9d07s1+8eoEd2YVfu68MT7FGWUTfP0EQb4OUfa9LQR bNKb/vjb6oEQuR2YLpIgbd8IssCumpsEmYAa4kve9xE0JTpPue4mbgFgUxwsl8Ibwda1 MkkQ== X-Gm-Message-State: ACgBeo0rkeABZiI0guUkezDokJpt3ExACQ/VXqncZJjq0F8DmKWSlUhm KACjn0wp1q7km4dJCcmEYRFv7dI6MTWcR1zIX0w= X-Google-Smtp-Source: AA6agR53abgJhbrjrkXXm8aoDOdt5N7ApLUDf8l8gdXWC5K0h+8H6Vmqk/EXucLiIPfbZRv7mEND0MbYtsaU/4RpswI= X-Received: by 2002:a05:6602:26c7:b0:67b:72ef:b87b with SMTP id g7-20020a05660226c700b0067b72efb87bmr1846439ioo.175.1660316243533; Fri, 12 Aug 2022 07:57:23 -0700 (PDT) MIME-Version: 1.0 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> <9674d00e-c0d6-ceba-feab-5dc475bda694@collabora.com> <73b51dde-689f-64ce-a1c8-0d7c84a2ed66@collabora.com> In-Reply-To: <73b51dde-689f-64ce-a1c8-0d7c84a2ed66@collabora.com> From: Rob Clark Date: Fri, 12 Aug 2022 07:57:11 -0700 Message-ID: Subject: Re: [PATCH v8 2/2] drm/gem: Don't map imported GEMs To: Dmitry Osipenko Cc: =?UTF-8?Q?Christian_K=C3=B6nig?= , =?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, Daniel Vetter 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 Fri, Aug 12, 2022 at 4:26 AM Dmitry Osipenko wrote: > > On 8/11/22 02:19, Rob Clark wrote: > > On Wed, Aug 10, 2022 at 3:23 PM Dmitry Osipenko > > wrote: > >> > >> On 8/11/22 01:03, Rob Clark wrote: > >>> On Wed, Aug 10, 2022 at 12:26 PM Dmitry Osipenko > >>> wrote: > >>>> > >>>> On 8/10/22 18:08, Rob Clark wrote: > >>>>> On Wed, Aug 10, 2022 at 4:47 AM Daniel Vetter wro= te: > >>>>>> > >>>>>> 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 K=C3=B6nig 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 i= mported into > >>>>>>>>>> Tegra's DRM GEM. > >>>>>>>>>> > >>>>>>>>>> Majority of DRM drivers prohibit mapping of the imported GEM o= bjects. > >>>>>>>>>> Mapping of imported GEMs require special care from userspace s= ince 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 D= RM drivers > >>>>>>>>>> for consistency. > >>>>>>>>>> > >>>>>>>>>> Suggested-by: Thomas Hellstr=C3=B6m > >>>>>>>>>> Signed-off-by: Dmitry Osipenko > >>>>>>>>> > >>>>>>>>> I'm pretty sure that this is the right approach, but it's certa= inly more > >>>>>>>>> than possible that somebody abused this already. > >>>>>>>> > >>>>>>>> I suspect that this is abused if you run deqp cts on android.. i= e. 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 displ= ay (or > >>>>>>>> dGPU+iGPU) because self-imports are handled differently in > >>>>>>>> drm_gem_prime_import_dev().. and maybe not in cases where you en= d 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 coul= d've > >>>>>>> map imported dma-bufs (Panfrost, Lima) and they already don't all= ow to > >>>>>>> do that, I think we're good. > >>>>>> > >>>>>> So can I have an ack from Rob here or are there still questions th= at 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'v= e 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 wo= n't > >>>>> be self-imports.. but I guess no one has tried to run android cts o= n > >>>>> panfrost). > >>>> > >>>> The last time I tried to mmap dma-buf imported to Panfrost didn't wo= rk > >>>> because Panfrost didn't implement something needed for that. I'll ne= ed > >>>> to take a look again because can't recall what it was. > Upd: I re-checked Panfrost using today's linux-next and mapping of > imported dma-buf works, I mapped imported buf from video decoder. > Apparently previously I had some local kernel change that broke the mappi= ng. > > >>>>> 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 initiall= y. > >>>> If neither of upstream DRM drivers need to map imported dma-bufs and > >>>> never needed, then why do we need this? > >>> > >>> oh, tegra isn't using shmem helpers? I assumed it was. Well my poin= t > >>> was to make a more targeted fail on tegra, and a WARN_ON for everyone > >>> else to make it clear that what they are doing is undefined behavior. > >>> Because so far existing userspace (or well, panfrost and freedreno at > >>> least, those are the two I know or checked) don't make special cases > >>> for mmap'ing against the dmabuf fd against the dmabuf fd instead of > >>> the drm device fd. > >> > >> It's not clear to me what bad Android does form yours comments. Does i= t > >> export dma-buf from GPU and then import it to GPU? If yes, then DRM co= re > >> has a check for the self-importing [1]. > >> > >> [1] > >> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_pri= me.c#L918 > >> > >> If you're meaning something else, then please explain in a more detail= s. > > > > So, android/gralloc allocates buffers externally to the driver and > > imports them into driver. (And that seems to not just be window > > surfaces, but in cases random textures, etc) > > > > In the normal case these should be allocated from drm/msm so it should > > hit [1].. this is the "dumb luck" I mentioned earlier. But I'm not > > confident enough to say that there is no other case. > > > >> > >>> I *think* it should work out that we don't hit this path with > >>> freedreno but on android I can't really guarantee or prove it. So > >>> your patch would potentially break existing working userspace. Maybe > >>> it is userspace that isn't portable (but OTOH it isn't like you are > >>> going to be using freedreno on tegra). So why don't you go for a mor= e > >>> targeted fix that only returns an error on hw where this is > >>> problematic? > >> > >> That's what the first versions of the patch did and Christian suggeste= d > >> that it's not a good approach. In fact it should be not only Tegra tha= t > >> has a broken dma-buf mapping, but apparently OMAP driver too. > > > > Hmm, I guess I'm a bit more conservative when it comes to potentially > > breaking userspace. > > If such userspace exists, then of course the mapping should continue to > work. Still will be great to know what that userpsace is. Definitely existing mesa does not have a special mmap path for imported dma-bufs (both in the case of panfrost and freedreno, I didn't check any others). The only question is whether there is a case where some app/test/etc imports a foreign dma-buf fd and then does something that would trigger mmap'ing, like readpix. BR, -R > Alright, let's keep the dma-buf mapping as-is for now. I'll fix just the > Tegra driver then. > > -- > Best regards, > Dmitry