From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bharata B Rao Subject: Re: PROBLEM: Power9: kernel oops on memory hotunplug from ppc64le guest Date: Sat, 18 May 2019 19:44:35 +0530 Message-ID: <20190518141434.GA22939@in.ibm.com> References: <16a7a635-c592-27e2-75b4-d02071833278@linux.vnet.ibm.com> Reply-To: bharata@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <16a7a635-c592-27e2-75b4-d02071833278@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: srikanth Cc: linuxppc-dev@lists.ozlabs.org, bharata@linux.vnet.ibm.com, mpe@ellerman.id.au, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org, npiggin@gmail.com, aneesh.kumar@linux.ibm.com List-Id: linux-next.vger.kernel.org On Thu, May 16, 2019 at 07:44:20PM +0530, srikanth wrote: > Hello, > > On power9 host, performing memory hotunplug from ppc64le guest results in > kernel oops. > > Kernel used : https://github.com/torvalds/linux/tree/v5.1 built using > ppc64le_defconfig for host and ppc64le_guest_defconfig for guest. > > Recreation steps: > > 1. Boot a guest with below mem configuration: >   33554432 >   8388608 >   4194304 >   >     >       >     >   > > 2. From host hotplug 8G memory -> verify memory hotadded succesfully -> now > reboot guest -> once guest comes back try to unplug 8G memory > > mem.xml used: > > > 8 > 0 > > > > Memory attach and detach commands used: >     virsh attach-device vm1 ./mem.xml --live >     virsh detach-device vm1 ./mem.xml --live > > Trace seen inside guest after unplug, guest just hangs there forever: > > [   21.962986] kernel BUG at arch/powerpc/mm/pgtable-frag.c:113! > [   21.963064] Oops: Exception in kernel mode, sig: 5 [#1] > [   21.963090] LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA > pSeries > [   21.963131] Modules linked in: xt_tcpudp iptable_filter squashfs fuse > vmx_crypto ib_iser rdma_cm iw_cm ib_cm ib_core libiscsi scsi_transport_iscsi > ip_tables x_tables autofs4 btrfs zstd_decompress zstd_compress lzo_compress > raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx > xor raid6_pq multipath crc32c_vpmsum > [   21.963281] CPU: 11 PID: 316 Comm: kworker/u64:5 Kdump: loaded Not > tainted 5.1.0-dirty #2 > [   21.963323] Workqueue: pseries hotplug workque pseries_hp_work_fn > [   21.963355] NIP:  c000000000079e18 LR: c000000000c79308 CTR: > 0000000000008000 > [   21.963392] REGS: c0000003f88034f0 TRAP: 0700   Not tainted (5.1.0-dirty) > [   21.963422] MSR:  800000000282b033   CR: > 28002884  XER: 20040000 > [   21.963470] CFAR: c000000000c79304 IRQMASK: 0 > [   21.963470] GPR00: c000000000c79308 c0000003f8803780 c000000001521000 > 0000000000fff8c0 > [   21.963470] GPR04: 0000000000000001 00000000ffe30005 0000000000000005 > 0000000000000020 > [   21.963470] GPR08: 0000000000000000 0000000000000001 c00a000000fff8e0 > c0000000016d21a0 > [   21.963470] GPR12: c0000000016e7b90 c000000007ff2700 c00a000000a00000 > c0000003ffe30100 > [   21.963470] GPR16: c0000003ffe30000 c0000000014aa4de c00a0000009f0000 > c0000000016d21b0 > [   21.963470] GPR20: c0000000014de588 0000000000000001 c0000000016d21b8 > c00a000000a00000 > [   21.963470] GPR24: 0000000000000000 ffffffffffffffff c00a000000a00000 > c0000003ffe96000 > [   21.963470] GPR28: c00a000000a00000 c00a000000a00000 c0000003fffec000 > c00a000000fff8c0 > [   21.963802] NIP [c000000000079e18] pte_fragment_free+0x48/0xd0 > [   21.963838] LR [c000000000c79308] remove_pagetable+0x49c/0x5b4 > [   21.963873] Call Trace: > [   21.963890] [c0000003f8803780] [c0000003ffe997f0] 0xc0000003ffe997f0 > (unreliable) > [   21.963933] [c0000003f88037b0] [0000000000000000] (null) > [   21.963969] [c0000003f88038c0] [c00000000006f038] > vmemmap_free+0x218/0x2e0 > [   21.964006] [c0000003f8803940] [c00000000036f100] > sparse_remove_one_section+0xd0/0x138 > [   21.964050] [c0000003f8803980] [c000000000383a50] > __remove_pages+0x410/0x560 > [   21.964093] [c0000003f8803a90] [c000000000c784d8] > arch_remove_memory+0x68/0xdc > [   21.964136] [c0000003f8803ad0] [c000000000385d74] > __remove_memory+0xc4/0x110 > [   21.964180] [c0000003f8803b10] [c0000000000d44e4] > dlpar_remove_lmb+0x94/0x140 > [   21.964223] [c0000003f8803b50] [c0000000000d52b4] > dlpar_memory+0x464/0xd00 > [   21.964259] [c0000003f8803be0] [c0000000000cd5c0] > handle_dlpar_errorlog+0xc0/0x190 > [   21.964303] [c0000003f8803c50] [c0000000000cd6bc] > pseries_hp_work_fn+0x2c/0x60 > [   21.964346] [c0000003f8803c80] [c00000000013a4a0] > process_one_work+0x2b0/0x5a0 > [   21.964388] [c0000003f8803d10] [c00000000013a818] > worker_thread+0x88/0x610 > [   21.964434] [c0000003f8803db0] [c000000000143884] kthread+0x1a4/0x1b0 > [   21.964468] [c0000003f8803e20] [c00000000000bdc4] > ret_from_kernel_thread+0x5c/0x78 > [   21.964506] Instruction dump: > [   21.964527] fbe1fff8 f821ffd1 78638502 78633664 ebe90000 7fff1a14 > 395f0020 813f0020 > [   21.964569] 7d2907b4 7d2900d0 79290fe0 69290001 <0b090000> 7c0004ac > 7d205028 3129ffff > [   21.964613] ---[ end trace aaa571aa1636fee6 ]--- > [   21.966349] > [   21.966383] Sending IPI to other CPUs > [   21.978335] IPI complete > [   21.981354] kexec: Starting switchover sequence. > I'm in purgatory git bisect points to commit 4231aba000f5a4583dd9f67057aadb68c3eca99d Author: Nicholas Piggin Date: Fri Jul 27 21:48:17 2018 +1000 powerpc/64s: Fix page table fragment refcount race vs speculative references The page table fragment allocator uses the main page refcount racily with respect to speculative references. A customer observed a BUG due to page table page refcount underflow in the fragment allocator. This can be caused by the fragment allocator set_page_count stomping on a speculative reference, and then the speculative failure handler decrements the new reference, and the underflow eventually pops when the page tables are freed. Fix this by using a dedicated field in the struct page for the page table fragment allocator. Fixes: 5c1f6ee9a31c ("powerpc: Reduce PTE table memory wastage") Cc: stable@vger.kernel.org # v3.10+ Regards, Bharata.