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Fri, 30 Jan 2026 05:46:10 +0000 Received: from smtpav04.fra02v.mail.ibm.com (smtpav04.fra02v.mail.ibm.com [10.20.54.103]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 60U5k6l036897200 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 30 Jan 2026 05:46:06 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A1BA52004B; Fri, 30 Jan 2026 05:46:06 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9EEC42004D; Fri, 30 Jan 2026 05:46:05 +0000 (GMT) Received: from li-218185cc-29b5-11b2-a85c-9a1300ae2e6e.in.ibm.com (unknown [9.109.215.162]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 30 Jan 2026 05:46:05 +0000 (GMT) From: Donet Tom To: gbatra@linux.ibm.com Cc: linuxppc-dev@lists.ozlabs.org, maddy@linux.ibm.com, Donet Tom Subject: Re: [PATCH] powerpc/iommu: bypass DMA APIs for coherent allocations for pre-mapped memory Date: Fri, 30 Jan 2026 11:16:02 +0530 Message-ID: <20260130054602.21331-1-donettom@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251107161105.85999-1-gbatra@linux.ibm.com> References: <20251107161105.85999-1-gbatra@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Z4vh3XRA c=1 sm=1 tr=0 ts=697c45a3 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=vUbySO9Y5rIA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=5ow3zEcTcvu9A-jyJV8A:9 X-Proofpoint-GUID: fRVW-NjcxcxTKs9xLBhWdFGgVMPwNP2d X-Proofpoint-ORIG-GUID: fRVW-NjcxcxTKs9xLBhWdFGgVMPwNP2d X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTMwMDA0MCBTYWx0ZWRfX7zVsLA0pw/qu jco5lfwMeQ3EceWmnwZNZUyXMs/0fS2ow93RyTW9DdvgQ/rzuI6rAQNs8nbff5uuUfcYZsXbL9R bpqpx/D4aoI5xg5BtjTtWitNPH2A8p/p2UUiCemOujDcwnbgUh6CuktSNZtjz2LYGsptAefpxpO 63sRFjRT5QBz8cYPJrcruX/Xf3/N2YpSDmDo3wcWnSeHrY4uE/H4D+N8XOHKlXIYylbMF3SEb67 I5DjtmK/JJPPS8/1OfLIBbOkEO9ElWse6TXfAL5dhxfEmJEB1Mh3uO/0ZIzpUup7odnZXdpV72A loqPWEp/DzEBOY60scaLz1I3PKKcuhGSdAMRtjdPDY06lx6ju4sCQcvpHmT4OHrVLHMUhqLu/xm MagpczncpqzdlnB4axx0Ew/v5jiLvkS42QUZFtllmlb1tMOAMZudfdsFCBNQ+xV7kZCkCUt1fCA dhFq0cq3zo8d11u4alw== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-01-29_03,2026-01-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 phishscore=0 priorityscore=1501 bulkscore=0 adultscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2601300040 On Fri, 07 Nov 2025 10:11:05 -0600, Gaurav Batra wrote: > Leverage ARCH_HAS_DMA_MAP_DIRECT config option for coherent allocations as > well. This will bypass DMA ops for memory allocations that have been > pre-mapped. > > Always set device bus_dma_limit when memory is pre-mapped. In some > architectures, like PowerPC, pmemory can be converted to regular memory via > daxctl command. This will gate the coherent allocations to pre-mapped RAM > only, by dma_coherent_ok(). > > [...] Even though this patch is now merged. But FWIW, I had verified this on my system and it fixed the iommu_alloc failure problem for me. So Tested-by: Donet Tom -- 2.52.0