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 93C49C32789 for ; Tue, 23 Aug 2022 18:27:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229494AbiHWS1d (ORCPT ); Tue, 23 Aug 2022 14:27:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231714AbiHWS1K (ORCPT ); Tue, 23 Aug 2022 14:27:10 -0400 Received: from mail-oi1-x22c.google.com (mail-oi1-x22c.google.com [IPv6:2607:f8b0:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D415A4B0D8; Tue, 23 Aug 2022 09:47:20 -0700 (PDT) Received: by mail-oi1-x22c.google.com with SMTP id v125so16737179oie.0; Tue, 23 Aug 2022 09:47:20 -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=F8aKSZv1NL2MA13LWlrkZ0pyLx1poLLo5+Y2auoHrrU=; b=P8Rb6AIUe0BqjayXQEF1C99U0H8YdtTbPpCkW0bERtLUXN9fooVIer4M3R47yIez/U 5go1SSUpqQGPaOv6AsSeoRoo8SSXNjtCuLMuvgFbBFBYml0t9Zq+e/kHUBIQ0wfa8LYs 0fCx1wsNmzKkwaquNleJdBdp/70ylcTVBYNrU8zsojU/8KiNhBozHLIiD/2vU3pbT1wu StvBfAQHmAvHRbTuuK1wfmyQdce5xlUhPz7Wu2Sg+hL+upMM0Ba5GeaTuFECDP5vlgsZ YyBmWB3oQyTquXWCh6CmFcUYquSC+NBylzyFgiUJ+4/FyXltqM8D6PhNC6TwsFN+ykfp 1FEA== 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=F8aKSZv1NL2MA13LWlrkZ0pyLx1poLLo5+Y2auoHrrU=; b=imTmjnlgp7XAz6NZ4y7cee8Lm2aEEqNIJbVPgWBQBgN2kgFBdt1LEe2kkuGllDW47y 8IbxgLMtCtu62EPCpSKeRrLbjI2HsroMke7aZ9bkreKBp7oic8lfHyLAyz1lIbUbT83U QgQYLh7y2re9ko0CSxa+TvANlNZvtS98JxyABC4X61BdCKehvfXikAs7D5BXtFCWoSG8 b+yydJzIWU1+IKfMJ/1kL7FTORWymWh8A4hj6YbbJIny3lTuIUvorVJPO6JqT4lsxuie tlr8HzENzVYdRa7sx726Z/ZfrMUDHNemXT2AFbZic+kkASVw4kGFQ6oMSp2fUijDfjZf mtuQ== X-Gm-Message-State: ACgBeo3rgRuj1EU92w5FsKqUJxuWqBjyAYs5Lodx5XpZKwe27WyEJKdU X5ygXT9958PSes5e2Y/iQKwJqoeAUV8Hl7I5S1E= X-Google-Smtp-Source: AA6agR7cQ1HWOR/GP2rtEG15PGZ/r+13Je3nF5uNZRRMMJwUkE+V9G7UTyql1pmHzDQiRGHyVzqd9qmK0bsICHBqrYU= X-Received: by 2002:a05:6808:238d:b0:344:e5f9:db34 with SMTP id bp13-20020a056808238d00b00344e5f9db34mr1650387oib.183.1661273240141; Tue, 23 Aug 2022 09:47:20 -0700 (PDT) MIME-Version: 1.0 References: <20220701090240.1896131-1-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> <5f118e10-db7a-a128-1e87-c9dddb65b2ac@collabora.com> <2ce5ff0a-9ab2-d146-04db-487a64714fce@gmail.com> <5988bf07-dd2e-a7ad-1ed9-831a402c3c5d@gmail.com> In-Reply-To: <5988bf07-dd2e-a7ad-1ed9-831a402c3c5d@gmail.com> From: Rob Clark Date: Tue, 23 Aug 2022 09:47:53 -0700 Message-ID: Subject: Re: [PATCH v8 2/2] drm/gem: Don't map imported GEMs To: =?UTF-8?Q?Christian_K=C3=B6nig?= Cc: Dmitry Osipenko , =?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 Tue, Aug 23, 2022 at 3:01 AM Christian K=C3=B6nig wrote: > > Am 22.08.22 um 19:26 schrieb Dmitry Osipenko: > > On 8/16/22 22:55, Dmitry Osipenko wrote: > >> On 8/16/22 15:03, Christian K=C3=B6nig wrote: > >>> Am 16.08.22 um 13:44 schrieb Dmitry Osipenko: > >>>> [SNIP] > >>>>> The other complication I noticed is that we don't seem to keep arou= nd > >>>>> the fd after importing to a GEM handle. And I could imagine that > >>>>> doing so could cause issues with too many fd's. So I guess the bes= t > >>>>> thing is to keep the status quo and let drivers that cannot mmap > >>>>> imported buffers just fail mmap? > >>>> That actually should be all the drivers excluding those that use > >>>> DRM-SHMEM because only DRM-SHMEM uses dma_buf_mmap(), that's why it > >>>> works for Panfrost. I'm pretty sure mmaping of imported GEMs doesn't > >>>> work for the MSM driver, isn't it? > >>>> > >>>> Intel and AMD drivers don't allow to map the imported dma-bufs. Both > >>>> refuse to do the mapping. > >>>> > >>>> Although, AMDGPU "succeeds" to do the mapping using > >>>> AMDGPU_GEM_DOMAIN_GTT, but then touching the mapping causes bus faul= t, > >>>> hence mapping actually fails. I think it might be the AMDGPU > >>>> driver/libdrm bug, haven't checked yet. > >>> That's then certainly broken somehow. Amdgpu should nerve ever have > >>> allowed to mmap() imported DMA-bufs and the last time I check it didn= 't. > >> I'll take a closer look. So far I can only tell that it's a kernel > >> driver issue because once I re-applied this "Don't map imported GEMs" > >> patch, AMDGPU began to refuse mapping AMDGPU_GEM_DOMAIN_GTT. > >> > >>>> So we're back to the point that neither of DRM drivers need to map > >>>> imported dma-bufs and this was never tested. In this case this patch= is > >>>> valid, IMO. > >> Actually, I'm now looking at Etnaviv and Nouveau and seems they should > >> map imported dma-buf properly. I know that people ran Android on > >> Etnaviv. So maybe devices with a separated GPU/display need to map > >> imported display BO for Android support. Wish somebody who ran Android > >> on one of these devices using upstream drivers could give a definitive > >> answer. I may try to test Nouveau later on. > >> > > Nouveau+Intel combo doesn't work because of [1] that says: > > > > "Refuse to fault imported pages. This should be handled (if at all) by > > redirecting mmap to the exporter." > > > > [1] > > https://elixir.bootlin.com/linux/v5.19/source/drivers/gpu/drm/ttm/ttm_b= o_vm.c#L154 > > > > Interestingly, I noticed that there are IGT tests which check prime > > mmaping of Nouveau+Intel [2] (added 9 years ago), but they fail as well= , > > as expected. The fact that IGT has such tests is interesting because it > > suggests that the mapping worked in the past. It's also surprising that > > nobody cared to fix the failing tests. For the reference, I checked > > v5.18 and today's linux-next. > > > > [2] > > https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/blob/master/tests/pr= ime_nv_test.c#L132 > > > > Starting subtest: nv_write_i915_cpu_mmap_read > > Received signal SIGBUS. > > Stack trace: > > #0 [fatal_sig_handler+0x163] > > #1 [__sigaction+0x50] > > #2 [__igt_unique____real_main354+0x406] > > #3 [main+0x23] > > #4 [__libc_start_call_main+0x80] > > #5 [__libc_start_main+0x89] > > #6 [_start+0x25] > > Subtest nv_write_i915_cpu_mmap_read: CRASH (0,005s) > > > > Starting subtest: nv_write_i915_gtt_mmap_read > > Received signal SIGBUS. > > Stack trace: > > #0 [fatal_sig_handler+0x163] > > #1 [__sigaction+0x50] > > #2 [__igt_unique____real_main354+0x33d] > > #3 [main+0x23] > > #4 [__libc_start_call_main+0x80] > > #5 [__libc_start_main+0x89] > > #6 [_start+0x25] > > Subtest nv_write_i915_gtt_mmap_read: CRASH (0,004s) > > > > I'm curious about the Etnaviv driver because it uses own shmem > > implementation and maybe it has a working mmaping of imported GEMs sinc= e > > it imports the dma-buf pages into Entaviv BO. Although, it should be > > risking to map pages using a different caching attributes (WC) from the > > exporter, which is prohibited on ARM ad then one may try to map importe= d > > udmabuf. > > > > Apparently, the Intel DG TTM driver should be able to map imported > > dma-buf because it sets TTM_TT_FLAG_EXTERNAL_MAPPABLE. > > Even with that flag set it is illegal to map the pages directly by an > importer. > > If that ever worked then the only real solution is to redirect mmap() > calls on importer BOs to dma_buf_mmap(). Yeah, I think this is the best option. Forcing userspace to hang on to the fd just in case someone calls readpix would be pretty harsh. BR, -R > Regards, > Christian. > > > > > Overall, it still questionable to me whether it's worthwhile to allow > > the mmaping of imported GEMs since only Panfrost/Lima can do it out of > > all drivers and h/w that I tested. Feels like drivers that can do the > > mapping have it just because they can and not because they need. > > >