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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-771f9f289c3sm1329536b3a.19.2025.08.26.02.44.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Aug 2025 02:44:46 -0700 (PDT) Message-ID: Date: Tue, 26 Aug 2025 17:44:42 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US From: Baochen Qiang Subject: is dma_mapping_error() check necessary for dma_alloc_noncoherent()? To: Marek Szyprowski , Robin Murphy , Jeff Johnson Cc: iommu@lists.linux.dev, "linux-kernel@vger.kernel.org >> linux-kernel" , "ath11k@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODIzMDAzNCBTYWx0ZWRfX0cKkk+L7om7q hb4ZJtAFlWz5+AIlQWC+WPbqtlBZhbvzMAOyG/M4N24F6V/SiuwqWDVyJKy/RSQguCW8p0qrk1d 5w4mImnavnRxIwWmpPpFArJD7d7KSIzOpCAp9edfZcsn0yoYuVFrt0uX80K5Upensb8FhWLiFJc ASHGDIFXPTEE2C/53VFisxiacNdzmZdPyf8npSnVQOYFtjMnkj9wqq6qf9eSNs7NxBBYSU1lMoI fFcbFl2XZXKLN8rfI64e4uz4g+5bCQMM93S5QGZBazDuZnCIJIXkMhbKCRo3W9k9tCUqoxq9GLx CjDN4plCHXrQ90akiWIPmvo7AXGR237ZGUVcMk+rI2Z26kU7kP7jBLZJhUufNnr3znX6va1pVib bg0Cw6R3 X-Proofpoint-GUID: bjKeJhQtm_BlDqBASYzr9Ze3swkuCcaP X-Authority-Analysis: v=2.4 cv=K+AiHzWI c=1 sm=1 tr=0 ts=68ad8210 cx=c_pps a=rEQLjTOiSrHUhVqRoksmgQ==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=Q74vz0maYr0LruRLZiwA:9 a=QEXdDO2ut3YA:10 a=2VI0MkxyNR6bbpdq8BZq:22 X-Proofpoint-ORIG-GUID: bjKeJhQtm_BlDqBASYzr9Ze3swkuCcaP 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 malwarescore=0 suspectscore=0 bulkscore=0 clxscore=1015 adultscore=0 impostorscore=0 priorityscore=1501 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508230034 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()?