From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 35A94471400; Thu, 24 Sep 2026 10:28:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790245704; cv=none; b=eiqFQCbGGkkrWlIG558rnaVr+ubRWr6a9/mT+Dm1H45cFzod2sN1TzijFP1L6PoeuCjn06UhtvIFjtl6EETjEYtFBKn6TWr4NIeVIeLfdDX82xUdtKr29k8AL4l7gGzbqvVycE9FoE7c958H0YDv7GE/WKtgpDn6t6DcWBYbfSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790245704; c=relaxed/simple; bh=TFe/rkio0Xb7YAAPo9GyCH1G11f02LaQiYMT79+8PkE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RiR++rqoFICTi5q0A9HakfKUAOqJcBw5mZUUqxE+VXBbYV8QRmdVU0nzlCT4terptARR1k41gy3qOHdwkbgw5+TKRDCPjBXuBZkNK8+M8RazzpgWSDygdPwdWIaejPppOpQKHTF4G7AxEwilUcQSjBrjKjXEGBarSwMndmxtTQ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ehN9kY3S; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ehN9kY3S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37CA21F000FF; Thu, 24 Sep 2026 10:28:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790245702; bh=RO3pD7Q9+eQAPt4mIEHLCPHWj9ylSpQSd8EUvJUV68k=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ehN9kY3S16mwiPpWIqXUBkd5hPCW7NXCUfm9dHVmmKs4VS6gwEyV4j4nHHdB+cYCq smsa3uzpTXcx7YKAzxQk6HHTQ//Ny2fNiiO3UgY4qY0oXBC0fbqcxW4LbvNnqbRLgd Fxy36ADnplqbxDgOAPCO7KWlW5sOPi1dz1GMuiwRJazYJvcZCYM3ebKF/AotMiau7N 50lAdyTvxvOOCn5e3y6C2VUacOASKaVi+8smHAh3g+dQSzGsvdX6Y2i0IbvLPQ4Q0P yXNKFB7X9cBLMsdR1N0cmttdd9NOplVn2yGzyY/5Wje2139C1/kKvbME3lAvh36cOH g1xCKrxl/idMw== Message-ID: <19a05a1e-6d27-40ad-bb61-b7ff4e3ddbb9@kernel.org> Date: Thu, 24 Sep 2026 11:28:17 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 1/2] dma-buf: keep DMABUF_DEBUG off by default To: Jianfeng Liu , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Cc: linux-arm-msm@vger.kernel.org, Jessica Zhang , Sumit Semwal , linaro-mm-sig@lists.linaro.org, =?UTF-8?Q?Christian_K=C3=B6nig?= , Rob Clark , Sean Paul , Simona Vetter , freedreno@lists.freedesktop.org, Marijn Suijten , David Airlie , Dmitry Baryshkov , Abhinav Kumar , Karl Mehltretter References: <20260923074256.9357-1-liujianfeng1994@gmail.com> <20260923074256.9357-2-liujianfeng1994@gmail.com> From: Bryan O'Donoghue Content-Language: en-GB Autocrypt: addr=bod@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 23/09/2026 08:42, Jianfeng Liu wrote: > Commit 143755bdabaa9 ("dma-buf: Make DMABUF_DEBUG default to y on > DEBUG_KERNEL kernels") fixed a dangling reference in the DMABUF_DEBUG > default, which had the side effect of enabling the option (and with it > the page-stripping sg_table wrapper handed to importers) on every > kernel with DEBUG_KERNEL=y - i.e. virtually every distro kernel. > > drm/msm is broken by this: it maps imported dma-bufs into the GPU's > own pagetables with iommu_map_sgtable(), which needs the struct page > of the attachment sg_table, and it fills the GEM object's page array > through drm_prime_sg_to_page_array(). With the debug wrapper in > place both silently produce garbage (the wrapper zeroes sg->length, > so the page iterator yields nothing and an uninitialized array is > kept). The VM_BIND map job then fails asynchronously after userspace > has already enqueued GPU work referencing the mapping, which shows up > as an arm-smmu translation fault from UCHE, e.g.: > > gpu fault: ttbr0=000000088a889000 iova=000000010741c000 dir=READ > type=TRANSLATION source=UCHE > > This breaks hardware video decode (clapper, chromium) on Adreno > systems; bisected on a Snapdragon laptop as v7.3-rc3 good, > v7.3-rc4 bad, culprit 143755bdabaa9. > > Revert the default until importers that legitimately need to build > phys-based mappings have been converted. > > Fixes: 143755bdabaa9 ("dma-buf: Make DMABUF_DEBUG default to y on DEBUG_KERNEL kernels") > Signed-off-by: Jianfeng Liu This is a very obviously LLM generated patch. Please state so in the commit log. Also I don't believe reverting the change is correct. Fix the bug where it exists in Adreno. --- bod