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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: aN4T9DGkggG4gTSFxpsFy0li-llBHITp X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIxMDAxOCBTYWx0ZWRfX4/ekYuLP0jTS gfp9csY5GMnBqfzt50/Jn0pvXDa/D3GQiPkoyfw9lrPWTCQCTznGBLoDZKAB8z7LbHQzxOdf0UD ZdXJvkKI5gb/WQKn38y5OeTcQRu3DsA= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIxMDAxOCBTYWx0ZWRfX5YLm0P8pI1zz RNMCP7xdAfJDzf6yT+bJ8sqjcs6HWse3K0afsDQVQAkCCAvwv+Ixqc95IjdBlLrlD7y6H8va/jH EisrwZ+tOCB4MBQribT3Ihbg3mfRHwdKCFc4X8bZwSgvKkAxo/gEtxwmmIhnoPQSQg1+pVLg0ge p1i2cfPBHjvApCj/NXfv5/7HddSbCpoeznez/Ffmy/F1xZn8B6uSluPEFydSDLHSYrLRPQU0/9P a9ZDMYfTb62gPBJIi07HTVB+rtfBKVgLQl4xRdx43mjuqqgztl9Ff3tv9QDfRV669HE2KalqMSO y0tc7po+mOHLZux8FuHF/c6SVgufpcer4Aciw5qLNWozZvW9686//g1I+1QpSm9zIE/7/pow6tW uLrfiLZXzIQIqoV3YSpb2C6i08R/VV2pmlEKHzsXGELNEkR51PlQdVXmfujpRXg7RIDVYiYMi1J D+UmGl+6+95y29KzsYA== X-Proofpoint-ORIG-GUID: 3_2FMnQbRqIzSRLEGfDujs0GFUx0wl7r X-Authority-Analysis: v=2.4 cv=Ob4NnRTY c=1 sm=1 tr=0 ts=6ad84695 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=vggBfdFIAAAA:8 a=Z4Rwk6OoAAAA:8 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=7ipKWUHlAAAA:8 a=voM4FWlXAAAA:8 a=rxpbpe3YEeMVxz9nh0AA:9 a=QEXdDO2ut3YA:10 a=HkZW87K1Qel5hWWM3VKY:22 a=gpc5p9EgBqZVLdJeV_V1:22 a=IC2XNlieTeVoXbcui8wp:22 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=2026-10-21_01,2026-10-19_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 phishscore=0 spamscore=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 priorityscore=1501 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610210018 X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 12/10/26 20:00, Pratyush Yadav wrote: > On Mon, Sep 28 2026, Sourabh Jain wrote: > >> KHO requires the scratch alignment to be at least CMA_MIN_ALIGNMENT_BYTES, >> and this is currently enforced with a static_assert(). >> >> That assertion breaks the build on powerpc once CONFIG_KEXEC_HANDOVER is >> enabled together with CONFIG_TRANSPARENT_HUGEPAGE or CONFIG_HUGETLB_PAGE: >> >> kernel/liveupdate/kexec_handover.c:49:39: error: expression in static assertion is not constant >> 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); >> ./include/linux/build_bug.h:80:56: note: in definition of macro '__static_assert' >> 80 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg) >> | ^~~~ >> kernel/liveupdate/kexec_handover.c:49:1: note: in expansion of macro 'static_assert' >> 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); >> >> CMA_MIN_ALIGNMENT_BYTES depends on pageblock_order, which is not a >> compile-time constant with certain configs, such as >> CONFIG_HUGETLB_PAGE_SIZE_VARIABLE on powerpc. The next patch in this >> series enables KHO on powerpc, so the alignment must be checked at >> runtime instead. >> >> Replace the static_assert() with a runtime check at the start of >> kho_reserve_scratch(), before any scratch memory is reserved. If the >> scratch alignment is smaller than the CMA minimum alignment, warn once >> and disable KHO rather than continue with a misaligned reservation. >> >> 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: linux-kernel@vger.kernel.org >> Cc: linuxppc-dev@lists.ozlabs.org >> Signed-off-by: Sourabh Jain >> --- >> kernel/liveupdate/kexec_handover.c | 23 +++++++++++++++-------- >> 1 file changed, 15 insertions(+), 8 deletions(-) >> >> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c >> index 7c4d86daf86d..dc76dd6b74da 100644 >> --- a/kernel/liveupdate/kexec_handover.c >> +++ b/kernel/liveupdate/kexec_handover.c >> @@ -39,15 +39,7 @@ >> #include "../kexec_internal.h" >> #include "kexec_handover_internal.h" >> >> -/* >> - * This is the minimal alignment required by deferred struct page init. >> - * deferred_init_memmap_chunk frees memory to the buddy allocator, which looks >> - * at the neighboring pages (up to MAX_PAGE_ORDER) to merge them. >> - * If KHO scratch is not aligned to that value, buddy can access uninitialized >> - * struct pages, which can cause a crash. >> - */ >> #define SCRATCH_ALIGNMENT_BYTES (PAGE_SIZE * MAX_ORDER_NR_PAGES) >> -static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); >> >> /* The magic token for preserved pages */ >> #define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */ >> @@ -836,6 +828,21 @@ static void __init kho_reserve_scratch(void) >> if (!kho_enable) >> return; >> >> + /* >> + * This is the minimal alignment required by deferred struct page init. >> + * deferred_init_memmap_chunk frees memory to the buddy allocator, which looks >> + * at the neighboring pages (up to MAX_PAGE_ORDER) to merge them. >> + * If KHO scratch is not aligned to that value, buddy can access uninitialized >> + * struct pages, which can cause a crash. >> + */ >> + if (WARN_ON_ONCE(SCRATCH_ALIGNMENT_BYTES < CMA_MIN_ALIGNMENT_BYTES)) { > Nit: do we need both the WARN_ON_ONCE() and the pr_err()? Can't we drop > the WARN and keep the pr_err only? Yes pr_err is good enough. I will remove WARN_ON_ONCE()... > > LGTM otherwise. Thanks for the review. - Sourabh Jain > >> + pr_err("scratch alignment %lu < CMA minimum %lu, disabling\n", >> + (unsigned long)SCRATCH_ALIGNMENT_BYTES, >> + (unsigned long)CMA_MIN_ALIGNMENT_BYTES); >> + kho_enable = false; >> + return; >> + } >> + >> scratch_size_update(); >> >> /* FIXME: deal with node hot-plug/remove */