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Fri, 21 Aug 2026 10:56:18 +0000 (GMT) Received: from li-4f5ba44c-27d4-11b2-a85c-a08f5b49eada.bl1-in.ibm.com (unknown [9.123.14.142]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 21 Aug 2026 10:56:18 +0000 (GMT) From: Sourabh Jain To: linuxppc-dev@lists.ozlabs.org Cc: Sourabh Jain , Aditya Gupta , Alexander Graf , Andrew Morton , Baoquan He , "Christophe Leroy (CS GROUP)" , Hari Bathini , Madhavan Srinivasan , Mahesh Salgaonkar , Michael Ellerman , Mike Rapoport , Nicholas Piggin , Pasha Tatashin , Pratyush Yadav , "Ritesh Harjani (IBM)" , Shivang Upadhyay , Shrikanth Hegde , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 0/3] powerpc: initial support for Kexec HandOver (KHO) Date: Fri, 21 Aug 2026 16:26:06 +0530 Message-ID: <20260821105609.983622-1-sourabhjain@linux.ibm.com> X-Mailer: git-send-email 2.55.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=CpuPtH4D c=1 sm=1 tr=0 ts=6a882edb cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=vggBfdFIAAAA:8 a=Z4Rwk6OoAAAA:8 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=7ipKWUHlAAAA:8 a=JfrnYn6hAAAA:8 a=itPyUPzOZQCiFHcQqVsA:9 a=HkZW87K1Qel5hWWM3VKY:22 a=gpc5p9EgBqZVLdJeV_V1:22 a=1CNFftbPRP8L7MoqJWF3:22 X-Proofpoint-ORIG-GUID: tBgUdosthgsI5jkqkI59kDQIsTYp6i8S X-Proofpoint-GUID: kYZIQBmvG2oGwz1yYgI-96BusQj3Yuzy X-Proofpoint-Spam-Info: AW1haW4tMjYwODIxMDA3OCBTYWx0ZWRfX5+DmDqg9LvvX lT6QS5/Ud5155aFWHfylCLDeWHFdHAi0i7zSayZYF0ygMAEKMK9iv511FiIlsIep0xd6K2yNDI/ ZBjpkD31gOYUhDrPzoAvInfXZuaRUPU= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIxMDA3OCBTYWx0ZWRfX5RvJ/H9s3RmN GbTxMJX/2kqIh+84r5Zxx17qqnTSj4iXSPwSbXhC0WproFwHOr+A56AGcqJ7K/xGsTgu1JOi2nv 1BDjVUXhA0ApEp0MIcC5XdiOQbN0f93WjxsBzLRHt2MHDT/e9ZTqOcCjAeyptjpv5IlBC2rVzOo bhoSOW3+Z+vhty2GA3jQ2jLzWt9W5eb5DBA9eAI/9BzrJh4v3smM8l6KspN6rEJnvxvnmXxalwi jQ4CXo118VEBq/CProbt0sCTvQ4qkfzfJ5Q+mPGlPJKnl8GBhqnoZ46DQtqmmE9yi82anL7pADT Uzkvtxa98QEFrbA0cxFAm5rSNgUn/V3eNWfg/wIvI9aCycSuBs1PNbAYMK17wcWIm652KpV0KyT bjTEmrx3oY31V4hycV+3RPeFBzejOTTBiBRPOV3BMFAxIFqNm8iMZ3ywKIukznwq5nx3aUdGXUm M4P0x4Ey2wEWTcVBQBw== 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=2026-08-21_03,2026-08-21_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 bulkscore=0 malwarescore=0 phishscore=0 lowpriorityscore=0 spamscore=0 clxscore=1011 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608210078 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260821_035653_290672_ACC90558 X-CRM114-Status: GOOD ( 18.81 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org This series adds initial powerpc support for Kexec HandOver (KHO), allowing state to be preserved across kexec on powerpc. Posting as RFC because some of the patches are workarounds for issues I ran into, and I'd like input on how best to address them. Patch 1 is a small Kconfig fix needed to unblock patch 2. It won't be needed once the ordering problem described under patch 2 is addressed properly. Patch 2 wires up ARCH_SUPPORTS_KEXEC_HANDOVER and adds the code to retrieve the KHO FDT and scratch region from /chosen on boot. On powerpc, crashkernel memory is reserved very early, from arch-specific code, while KHO's scratch region is reserved later, from generic code (kho_memory_init()). Crashkernel reservation always runs first, so by the time KHO reserves its scratch region, not enough memory is left and the reservation fails. Until scratch reservation can be moved ahead of crashkernel reservation, this patch makes KHO and CRASH_DUMP mutually exclusive on powerpc as a stopgap. The failure scenario and the reasoning behind this restriction are described in the commit message with an example. Patch 3 excludes TRANSPARENT_HUGEPAGE and HUGETLB_PAGE from ARCH_SUPPORTS_KEXEC_HANDOVER, since KHO's static_assert() on SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES fails to build when either is enabled -- pageblock_order isn't a compile-time constant on powerpc in that configuration. With all three patches applied, CONFIG_TEST_KEXEC_HANDOVER passes on powerpc. Open questions I'd appreciate feedback on: - How should KHO scratch reservation and powerpc's crashkernel reservation be ordered so both can be enabled together, given that scratch reservation currently happens in generic code (kho_memory_init())? - Excluding THP/HUGETLB_PAGE is a workaround for the build failure. Looking for input on how to handle CMA_MIN_ALIGNMENT_BYTES when pageblock_order is non-constant. Cc: Aditya Gupta Cc: Alexander Graf Cc: Andrew Morton Cc: Baoquan He Cc: Christophe Leroy (CS GROUP) Cc: Hari Bathini Cc: Madhavan Srinivasan Cc: Mahesh Salgaonkar Cc: Michael Ellerman Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Pasha Tatashin Cc: Pratyush Yadav Cc: Ritesh Harjani (IBM) Cc: Shivang Upadhyay Cc: Shrikanth Hegde Cc: Sourabh Jain Cc: kexec@lists.infradead.org Cc: linux-kernel@vger.kernel.org Sourabh Jain (3): kernel/liveupdate: make KEXEC_HANDOVER depend on KEXEC_FILE instead of selecting it powerpc: add support for Kexec HandOver (KHO) powerpc/kho: exclude THP and HUGETLB_PAGE arch/powerpc/Kconfig | 6 ++++++ arch/powerpc/kernel/setup-common.c | 33 ++++++++++++++++++++++++++++++ kernel/liveupdate/Kconfig | 2 +- 3 files changed, 40 insertions(+), 1 deletion(-) -- 2.55.0