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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 7D473C624D0 for ; Wed, 2 Sep 2026 10:47:09 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B601F10E4A3; Wed, 2 Sep 2026 10:47:08 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="fZLwp5TZ"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id D62CA10E4A3 for ; Wed, 2 Sep 2026 10:47:06 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id E4072600D0; Wed, 2 Sep 2026 10:47:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3077A1F000E9; Wed, 2 Sep 2026 10:47:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788346025; bh=NMPfVN5CbaC96HtvVa8DpidRZa0TUnpKn2VRTVdV5ec=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fZLwp5TZrTiJ6QaK1nT8Uvuxd7F/m4iNUe4BaGRVzrqqkV/AEe2h29PAydWpqzWQs lFdlIjUmcRuF6eg6qGCTnjq0pBx/I5QgwP4oxJqqS/l87HMIt9FAhh14jpeNgBzazS ClOrKUJFgNFXnSE2ZUSysf5HwJ4OqShQWrBLgorw6WNEVVBzXxsEh4OL/pPGfxVavp i7Uii98uCb7VI3GLSNoxqsBLnMjAyvEOErZ+EHgoQ4pm+FfGwSlIeqgSepYMLfTK3R XZBEAByyFzXf5Nrp19c67P+hhLP0wFJnGfU5XPbLwUy8HgG3DqUQRNzBhowj2cN1pi 4uBYg4WeK+3sA== Message-ID: <275a55e8-543e-466d-a6a1-84776e763024@kernel.org> Date: Wed, 2 Sep 2026 12:47:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/9] dma-buf: add dma_fence_was_initialized function v2 To: phasta@kernel.org, =?UTF-8?Q?Christian_K=C3=B6nig?= , tursulin@ursulin.net, matthew.brost@intel.com, sumit.semwal@linaro.org Cc: dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org References: <20260120105655.7134-1-christian.koenig@amd.com> <20260120105655.7134-2-christian.koenig@amd.com> <0d40243b-0929-46d2-be85-e3248d4bd09c@kernel.org> <9edeaa17aebc284f1f171b1dd4d9ffee4721b750.camel@mailbox.org> <4b5b6dda-43a4-4488-9dbd-b0f92fcead61@kernel.org> <0b84716fa6bec4e38d811dc76926dd81e31e0c81.camel@mailbox.org> <5dd4248bccb446ef390e7149649632657db4aaae.camel@mailbox.org> <0df59c80-ae58-47d3-a96b-e878a17766a7@kernel.org> <5be2d5f9-579f-4c5c-8463-a2505a6f0c74@kernel.org> <307d764629d7c5d2704b7897c8c0c32c1ef4ce33.camel@mailbox.org> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 02. 09. 26, 9:03, Philipp Stanner wrote: > On Wed, 2026-09-02 at 08:56 +0200, Jiri Slaby wrote: >> On 02. 09. 26, 8:52, Philipp Stanner wrote: >>> On Fri, 2026-08-28 at 10:32 +0200, Jiri Slaby wrote: >>>> On 28. 08. 26, 9:46, Jiri Slaby wrote: >>>>> What helps is indeed the revert back to: >>>>> >>>>> --- a/drivers/gpu/drm/qxl/qxl_release.c >>>>> +++ b/drivers/gpu/drm/qxl/qxl_release.c >>>>> @@ -147,7 +147,7 @@ qxl_release_free(struct qxl_device *qdev, >>>>>           idr_remove(&qdev->release_idr, release->id); >>>>>           spin_unlock(&qdev->release_idr_lock); >>>>> >>>>> -       if (dma_fence_was_initialized(&release->base)) { >>>>> +       if (release->base.ops) { >>>> >>>> Crap, the flags simple got garbage from previous freed buffer, so: >>>> -       release = kmalloc(size, GFP_KERNEL); >>>> +       release = kzalloc(size, GFP_KERNEL); >>>> >>>> fixes this of course. Patch coming. >>>> >>>> Now, the ops and initialized are either both set or unset: >>>> qxl_release_free 1: release->base.ops=0x0 initialized=0 id=6 type=2 >>>> qxl_release_free 1: release->base.ops=qxl_fence_ops initialized=1 id=2 >>>> type=0 >>>> >>>> Unlike before. >>>> >>>> FTR release->base.ops were NULLed after that kmalloc. Unlike >>>> release->base.flags. >>> >>> You're saying that QXL is re-using that fence if it were uninitialized? >> >> Sort of. The fence was dropped and freed. Then a new memory was >> allocated. And garbage from that allocation was used -- it might be the >> old (freed) fence. Or anything else freed previously. Simply garbage. > > > Maybe even dma_fence_init() should zero out the memory for maximum > robustness. That would not help as dma_fence_init() is called too late or not at all here... dma_fence_init() is called late as the driver wants to call dma_fence_was_initialized() to distinguish the cases when the init was called and when not. > We do that in drm_sched at a few places. > > Opinions? @Christian? -- js suse labs