On 17/03/2023 14:12, Dan Williams wrote: > lizhijian@xxxxxxxxxxx wrote: > [..] >> Case D: unsupported && need your input To support this situation, the >> makedumpfile needs to know the location of metadata for each pmem >> namespace and the address and size of metadata in the pmem [start, >> end) > > My first reaction is that you should copy what the ndctl utility does > when it needs to manipulate or interrogate the metadata space. > > For example, see namespace_rw_infoblock():> > https://github.com/pmem/ndctl/blob/main/ndctl/namespace.c#L2022 > > That facility uses the force_raw attribute > ("/sys/bus/nd/devices/namespaceX.Y/force_raw") to arrange for the > namespace to initalize without considering any pre-existing metdata > *and* without overwriting it. In that mode makedumpfile can walk the > namespaces and retrieve the metadata written by the previous kernel. For the dumping application(makedumpfile or cp), it will/should reads /proc/vmcore to construct the dumpfile, So makedumpfile need to know the *address* and *size/end* of metadata in the view of 1st kernel address space. I haven't known much about namespace_rw_infoblock() , so it is also an option if we can know such information from it. My current WIP propose is to export a list linking all pmem namespaces to vmcore, with this, the kdump kernel don't need to rely on the pmem driver. Thanks Zhijian > > The module to block to allow makedumpfile to access the namespace in raw > mode is the nd_pmem module, or if it is builtin the > nd_pmem_driver_init() initcall.
