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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-246687b521bsm108143455ad.60.2025.08.26.18.55.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Aug 2025 18:55:26 -0700 (PDT) Message-ID: Date: Wed, 27 Aug 2025 09:55:20 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: is dma_mapping_error() check necessary for dma_alloc_noncoherent()? To: Marek Szyprowski , Baochen Qiang , Robin Murphy , Jeff Johnson Cc: iommu@lists.linux.dev, "linux-kernel@vger.kernel.org >> linux-kernel" , "ath11k@lists.infradead.org" References: <89954593-8236-464e-8848-e7cdcf639c0a@samsung.com> Content-Language: en-US From: Baochen Qiang In-Reply-To: <89954593-8236-464e-8848-e7cdcf639c0a@samsung.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODIzMDAzMyBTYWx0ZWRfXxBLR3ON2Bq+c 9leJcVXapTns3KVhnXZsZ/6Kuy+LgSP8yzAVkYc78Kp32yKhfUgeUmFPC03IqKNkQrqS8ragabF UEb19R99W3PIlZqgXPUs//0Y6KHMylNIn3t/DBZlKIJpuw7WsUNv4IDz1iiWVdSebZHBI37V+/4 KkzeEK/bskvtOaNoFzMBtA8ZSC9r2bXJ8Pgm4epvmIyA4AdFgFjpIZHsHHRi/zkc9nmwl9VTJXm KlpC0GA8rsdlwJ8chYFQnxx1d9mWzj2IRLdgGvdGg+btKSpsiF3U1+5+sMxSN7VnAUCrl7bLOaM hdRdNj7vZuBAY0s3M0ehq4lja/oQQmTcr+UDF0oNyTxy6kUl408ibDdGuZAuwpR4CNkk0mLMgDV h6sO2iy4 X-Authority-Analysis: v=2.4 cv=Lco86ifi c=1 sm=1 tr=0 ts=68ae6591 cx=c_pps a=Oh5Dbbf/trHjhBongsHeRQ==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=v1NiFcvVahR_jOWWQrIA:9 a=QEXdDO2ut3YA:10 a=_Vgx9l1VpLgwpw_dHYaR:22 X-Proofpoint-GUID: Q27ZIkOR2LoUK1qM9h7JUfjnE0wcnRAU X-Proofpoint-ORIG-GUID: Q27ZIkOR2LoUK1qM9h7JUfjnE0wcnRAU X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-26_02,2025-08-26_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 clxscore=1015 malwarescore=0 spamscore=0 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508230033 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250826_185530_225078_5A965AD7 X-CRM114-Status: GOOD ( 15.32 ) X-BeenThere: ath11k@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "ath11k" Errors-To: ath11k-bounces+ath11k=archiver.kernel.org@lists.infradead.org On 8/26/2025 10:09 PM, Marek Szyprowski wrote: > On 26.08.2025 11:44, Baochen Qiang wrote: >> Hi guys, >> >> I have a driver which allocate noncoherent DMA buffer and get the returned CPU addr tested: >> >> vaddr_unaligned = dma_alloc_noncoherent(ab->dev, rx_tid->unaligned_size, &paddr, >> DMA_BIDIRECTIONAL, GFP_ATOMIC); >> if (!vaddr_unaligned) { >> spin_unlock_bh(&ab->base_lock); >> return -ENOMEM; >> } >> >> while free the buffer >> >> dma_free_noncoherent(ab->dev, rx_tid->unaligned_size, >> rx_tid->vaddr_unaligned, >> rx_tid->paddr_unaligned, DMA_BIDIRECTIONAL); >> >> I get below warnings: >> >> DMA-API: ath11k_pci 0000:03:00.0: device driver failed to check map error[device >> address=0x00000000f3ad7000] [size=639 bytes] [mapped as single] >> WARNING: CPU: 15 PID: 64303 at kernel/dma/debug.c:1036 check_unmap+0x7e2/0x950 >> RIP: 0010:check_unmap+0x7e2/0x950 >> Call Trace: >> >> ? free_to_partial_list+0x9d/0x350 >> debug_dma_unmap_page+0xac/0xc0 >> ? debug_smp_processor_id+0x17/0x20 >> ? rcu_is_watching+0x13/0x70 >> dma_free_pages+0x56/0x180 >> [...] >> >> ---[ end trace 0000000000000000 ]--- >> DMA-API: Mapped at: >> debug_dma_map_page+0x7c/0x140 >> dma_alloc_pages+0x74/0x220 >> [...] >> >> Checking code gives me the impression that I should do dma_mapping_error() check as well. >> And indeed with below diff the warning is gone: >> >> + dma_mapping_error(ab->dev, paddr); >> >> However this does not make sense to me since IMO testing the CPU address is good enough, I >> can not imagine a valid case where DMA alloc/map fails while returning a valid CPU >> address, no? >> >> If I was right, should we remove invocation to debug_dma_map_page() in dma_alloc_pages()? > > Simply replace "if (!vaddr_unaligned)" with "if > dma_mapping_error(ab->dev, paddr)" and the debug code will be happy. Thanks, much better! But I am wondering if the debug code is worrying too much? isn't the CPU addr test already good enough? > > Best regards