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Thu, 13 Aug 2026 07:10:51 -0700 (PDT) Received: from hu-pkondeti-hyd.qualcomm.com ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-31ec082633fsm8518276eec.28.2026.08.13.07.10.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Aug 2026 07:10:51 -0700 (PDT) Date: Thu, 13 Aug 2026 19:40:41 +0530 From: Pavan Kondeti To: Will Deacon Cc: Catalin Marinas , Pavan Kondeti , Suzuki K Poulose , Steven Price , kvm@vger.kernel.org, kvmarm@lists.linux.dev, Marc Zyngier , James Morse , Oliver Upton , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo Pieralisi Subject: Re: [PATCH v16 07/45] arm64: mm: Handle Granule Protection Faults (GPFs) Message-ID: <8db602b8-7fd3-4c11-8fbd-3b8251648eb8@quicinc.com> References: <20260803134403.80630-1-steven.price@arm.com> <20260803134403.80630-8-steven.price@arm.com> <7d4e5920-aa20-40cd-954e-037631bd0d6c@quicinc.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Authority-Analysis: v=2.4 cv=EujiaycA c=1 sm=1 tr=0 ts=6a7dd06d cx=c_pps a=cmESyDAEBpBGqyK7t0alAg==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=VwQbUJbxAAAA:8 a=vggBfdFIAAAA:8 a=dIWtD5pVMjQwIhOhhukA:9 a=CjuIK1q_8ugA:10 a=1OuFwYUASf3TG4hYMiVC:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEzMDEwMSBTYWx0ZWRfX6jCE8XLcU3qD sDXwY1Br2yceP45nJJzC6CCXedtO9iBq3uI/rByX/B2FbnjfVGzm2OsTtLRc88q8k82EYBBsyvO AOYD3V+sNaX4Id4xiRXWJ4/BGS7Qhx8SNxYZhnVLShVqxRknFym9HNqwXK7hAgVDxMLvMltJyI6 OB6MP6vR4QsZGWgnyyQFKpSHpNGixLdj0wvnQV1M4qJWRUbxwMrhWt+hj2eeF82xR5xBIGNyfbV ACAK5pKDlVkNP1MMBGonZ0ny4YfGGx+Jy0AdDGpLPddN9H3QZgzOxjQCaQa4c3JuhOLE4oz0YGu pf5L3DHN39REI5iDigmYtZp21nrKeT9YLCf2U4dmRjZ7/tdZw5RfQ+5Vop2D0F1Ueii7cJjTTfr wGS1VKF1CTRy0lMZnmHlAUalcd/lF8gR4/oI3ZjE1K5KNw3HWoDe7X/FFXo1DnIcHMKUk+FNCkv /3SDVu45d1BtM3rwiGQ== X-Proofpoint-GUID: KcgRlEaIXeVL8jPg95kbhY-a3d1Wx3_t X-Proofpoint-ORIG-GUID: KcgRlEaIXeVL8jPg95kbhY-a3d1Wx3_t X-Proofpoint-Spam-Info: AW1haW4tMjYwODEzMDEwMSBTYWx0ZWRfX38GTdmNrTwdN l7QaDyBnU7aUzlzX1HdF9v14YUw9niu2ElhTd7sfw/H/RNe1/0q5qrneDDu7+oK76vcW7le9Tni Tf3AU+ivCvEKV/oThahaxgd3yMaLmhA= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-13_04,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 lowpriorityscore=0 suspectscore=0 bulkscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 adultscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608130101 On Thu, Aug 13, 2026 at 11:11:03AM +0100, Will Deacon wrote: > On Wed, Aug 12, 2026 at 02:51:29PM +0100, Catalin Marinas wrote: > > On Wed, Aug 12, 2026 at 06:12:09PM +0530, Pavan Kondeti wrote: > > > There is a valid case for fixup_exception() to be needed here in GPF > > > handling. > > > > > > -000 |load_unaligned_zeropad(inline) > > > -000 |hash_name(inline) > > > -000 |link_path_walk() > > > -001 |path_lookupat() > > > -002 |filename_lookup() > > > -003 |vfs_statx() > > > -004 |vfs_fstatat() > > > > > > We observed this in Android running Gunyah when the page is mapped in > > > EL1 but unmapped at EL2. path_lookupat() can actually handle this > > > via fixup_exeption() when a word load crosses the page boundary. > > > However, Gunyah injects a Synchronous External Abort and we have > > > a downstream patch [1] that adds fixup_exception() in do_sea(). pKVM > > > injects [2] such faults back to EL1 and fixup_exception() is taken care. > > > > Ah, good point, completely forgot about load_unaligned_zeropad(). Since > > we don't unmap the linear map for delegated pages, we'll need the > > fixup_exception(). And I guess warning in this case is not desirable > > either. We could limit it to EX_TYPE_KACCESS_ERR_ZERO and > > EX_TYPE_LOAD_UNALIGNED_ZEROPAD, though not sure it's worth it. > > Alternatively, I think the series to unmap guest memory from the linear > map would solve that for gmem: > > https://lore.kernel.org/all/20260410151746.61150-1-kalyazin@amazon.com/ > Thanks Will for sharing this information. There are use cases outside gmem like FF-A lend to Secure Partition. we may not be enforcing all such memory to be unmapped at EL1, correct? Thanks, Pavan