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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429952d5768sm26116915f8f.24.2025.10.29.02.57.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Oct 2025 02:57:16 -0700 (PDT) Message-ID: <6bbdf4ce-10e3-429b-89fc-ef000f118fec@redhat.com> Date: Wed, 29 Oct 2025 10:57:15 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] s390: fix HugeTLB vmemmap optimization crash To: Luiz Capitulino , hca@linux.ibm.com, borntraeger@linux.ibm.com, joao.m.martins@oracle.com, mike.kravetz@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com Cc: osalvador@suse.de, akpm@linux-foundation.org, aneesh.kumar@kernel.org References: <20251028211533.47694-1-luizcap@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20251028211533.47694-1-luizcap@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28.10.25 22:15, Luiz Capitulino wrote: > A reproducible crash occurs when enabling HugeTLB vmemmap optimization (HVO) > on s390. The crash and the proposed fix were worked on an s390 KVM guest > running on an older hypervisor, as I don't have access to an LPAR. However, > the same issue should occur on bare-metal. > > Reproducer (it may take a few runs to trigger): > > # sysctl vm.hugetlb_optimize_vmemmap=1 > # echo 1 > /proc/sys/vm/nr_hugepages > # echo 0 > /proc/sys/vm/nr_hugepages > > Crash log: > > [ 52.340369] list_del corruption. prev->next should be 000000d382110008, but was 000000d7116d3880. (prev=000000d7116d3910) > [ 52.340420] ------------[ cut here ]------------ > [ 52.340424] kernel BUG at lib/list_debug.c:62! > [ 52.340566] monitor event: 0040 ilc:2 [#1]SMP > [ 52.340573] Modules linked in: ctcm fsm qeth ccwgroup zfcp scsi_transport_fc qdio dasd_fba_mod dasd_eckd_mod dasd_mod xfs ghash_s390 prng des_s390 libdes sha3_512_s390 sha3_256_s390 virtio_net virtio_blk net_failover sha_common failover dm_mirror dm_region_hash dm_log dm_mod paes_s390 crypto_engine pkey_cca pkey_ep11 zcrypt pkey_pckmo pkey aes_s390 > [ 52.340606] CPU: 1 UID: 0 PID: 1672 Comm: root-rep2 Kdump: loaded Not tainted 6.18.0-rc3 #1 NONE > [ 52.340610] Hardware name: IBM 3931 LA1 400 (KVM/Linux) > [ 52.340611] Krnl PSW : 0704c00180000000 0000015710cda7fe (__list_del_entry_valid_or_report+0xfe/0x128) > [ 52.340619] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 > [ 52.340622] Krnl GPRS: c0000000ffffefff 0000000100000027 000000000000006d 0000000000000000 > [ 52.340623] 000000d7116d35d8 000000d7116d35d0 0000000000000002 000000d7116d39b0 > [ 52.340625] 000000d7116d3880 000000d7116d3910 000000d7116d3910 000000d382110008 > [ 52.340626] 000003ffac1ccd08 000000d7116d39b0 0000015710cda7fa 000000d7116d37d0 > [ 52.340632] Krnl Code: 0000015710cda7ee: c020003e496f larl %r2,00000157114a3acc > 0000015710cda7f4: c0e5ffd5280e brasl %r14,000001571077f810 > #0000015710cda7fa: af000000 mc 0,0 > >0000015710cda7fe: b9040029 lgr %r2,%r9 > 0000015710cda802: c0e5ffe5e193 brasl %r14,0000015710996b28 > 0000015710cda808: e34090080004 lg %r4,8(%r9) > 0000015710cda80e: b9040059 lgr %r5,%r9 > 0000015710cda812: b9040038 lgr %r3,%r8 > [ 52.340643] Call Trace: > [ 52.340645] [<0000015710cda7fe>] __list_del_entry_valid_or_report+0xfe/0x128 > [ 52.340649] ([<0000015710cda7fa>] __list_del_entry_valid_or_report+0xfa/0x128) > [ 52.340652] [<0000015710a30b2e>] hugetlb_vmemmap_restore_folios+0x96/0x138 > [ 52.340655] [<0000015710a268ac>] update_and_free_pages_bulk+0x64/0x150 > [ 52.340659] [<0000015710a26f8a>] set_max_huge_pages+0x4ca/0x6f0 > [ 52.340662] [<0000015710a273ba>] hugetlb_sysctl_handler_common+0xea/0x120 > [ 52.340665] [<0000015710a27484>] hugetlb_sysctl_handler+0x44/0x50 > [ 52.340667] [<0000015710b53ffa>] proc_sys_call_handler+0x17a/0x280 > [ 52.340672] [<0000015710a90968>] vfs_write+0x2c8/0x3a0 > [ 52.340676] [<0000015710a90bd2>] ksys_write+0x72/0x100 > [ 52.340679] [<00000157111483a8>] __do_syscall+0x150/0x318 > [ 52.340682] [<0000015711153a5e>] system_call+0x6e/0x90 > [ 52.340684] Last Breaking-Event-Address: > [ 52.340684] [<000001571077f85c>] _printk+0x4c/0x58 > [ 52.340690] Kernel panic - not syncing: Fatal exception: panic_on_oops > > This issue was introduced by commit f13b83fdd996 ("hugetlb: batch TLB > flushes when freeing vmemmap"). Before that change, the HVO > implementation called flush_tlb_kernel_range() each time a vmemmap > PMD split and remapping was performed. The mentioned commit changed this > to issue a few flush_tlb_all() calls after performing all remappings. > > However, on s390, flush_tlb_kernel_range() expands to > __tlb_flush_kernel() while flush_tlb_all() is not implemented. As a > result, we went from flushing the TLB for every remapping to no flushing > at all. > > This commit fixes this by implementing flush_tlb_all() on s390 as an > alias to __tlb_flush_global(). This should cause a flush on all TLB > entries on all CPUs as expected by the flush_tlb_all() semantics. > > Fixes: f13b83fdd996 ("hugetlb: batch TLB flushes when freeing vmemmap") > Signed-off-by: Luiz Capitulino > --- Nice finding! Makes me wonder whether the default flush_tlb_all() should actually map to a BUILD_BUG(), such that we don't silently not-flush on archs that don't implement it. Reviewed-by: David Hildenbrand -- Cheers David / dhildenb