On 16/03/2023 23:54, Dan Williams wrote: > Li Zhijian wrote: >> nvdimm_bus_register() could be called from other modules, such as nfit, >> but it can only be called after the nvdimm_bus_type is registered. >> >> BUG: kernel NULL pointer dereference, address: 0000000000000098 >> #PF: supervisor read access in kernel mode >> #PF: error_code(0x0000) - not-present page >> PGD 0 P4D 0 >> Oops: 0000 [#1] PREEMPT SMP PTI >> CPU: 0 PID: 117 Comm: systemd-udevd Not tainted 6.2.0-rc6-pmem+ #97 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS >> rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 >> RIP: 0010:bus_add_device+0x58/0x150 >> Call Trace: >> <TASK> >> device_add+0x3ac/0x980 >> nvdimm_bus_register+0x16d/0x1d0 >> acpi_nfit_init+0xb72/0x1f90 [nfit] >> acpi_nfit_add+0x1d5/0x200 [nfit] >> acpi_device_probe+0x45/0x160 > > Can you explain a bit more how to hit this crash? This has not been a > problem historically and the explanation above makes it sound like this > is a theoretical issue. >
Dan, Configure the kconfig with ACPI_NFIT [=m] && LIBNVDIMM [=y], and add extra kernel booting parameter 'initcall_blacklist=libnvdimm_init'. Then kernel panic! Theoretically, it will also happen if nvdimm_bus_register() failed. For kdump purpose[1], we need to disable libnvdimm driver to ensure metadata in pmem will not be updated again in kdump kernel [1]https://lore.kernel.org/linux-mm/3c752fc2-b6a0-2975-ffec-dba3edcf4...@fujitsu.com/T/ Thanks Zhijian > libnvdimm_init() *should* be done before the nfit driver can attempt > nvdimm_bus_register(). So, something else is broken if > nvdimm_bus_register() can be called before libnvdimm_init(), or after > libnvdimm_exit().
