[ add Ross ] On Thu, Oct 18, 2018 at 12:15 AM Kees Cook <keesc...@chromium.org> wrote: > > On Wed, Oct 17, 2018 at 5:49 PM, Dan Williams <dan.j.willi...@intel.com> > wrote: > > On Wed, Oct 17, 2018 at 5:29 PM Kees Cook <keesc...@chromium.org> wrote: > >> > >> When ramoops reserved a memory region in the kernel, it had an unhelpful > >> label of "persistent_memory". When reading /proc/iomem, it would be > >> repeated many times, did not hint that it was ramoops in particular, > >> and didn't clarify very much about what each was used for: > >> > >> 400000000-407ffffff : Persistent Memory (legacy) > >> 400000000-400000fff : persistent_memory > >> 400001000-400001fff : persistent_memory > >> ... > >> 4000ff000-4000fffff : persistent_memory > >> > >> Instead, this adds meaningful labels for how the various regions are > >> being used: > >> > >> 400000000-407ffffff : Persistent Memory (legacy) > >> 400000000-400000fff : ramoops:dump(0/252) > >> 400001000-400001fff : ramoops:dump(1/252) > >> ... > >> 4000fc000-4000fcfff : ramoops:dump(252/252) > >> 4000fd000-4000fdfff : ramoops:console > >> 4000fe000-4000fe3ff : ramoops:ftrace(0/3) > >> 4000fe400-4000fe7ff : ramoops:ftrace(1/3) > >> 4000fe800-4000febff : ramoops:ftrace(2/3) > >> 4000fec00-4000fefff : ramoops:ftrace(3/3) > >> 4000ff000-4000fffff : ramoops:pmsg > > > > Hopefully ramoops is doing request_region() before trying to do > > anything with its ranges, because it's going to collide with the pmem > > driver doing a request_region(). If we want to have pstore use pmem as > > a backing store that's a new drivers/nvdimm/ namespace personality > > driver to turn around and register a persistent memory range with > > pstore rather than the pmem block-device driver. > > Yup: it's using request_mem_region() (that's where the labels above > are assigned). > > As for nvdimm specifically, yes, I'd love to get pstore hooked up > correctly to nvdimm. How do the namespaces work? Right now pstore > depends one of platform driver data, device tree specification, or > manual module parameters.
>From the userspace side we have the ndctl utility to wrap personalities on top of namespaces. So for example, I envision we would be able to do: ndctl create-namespace --mode=pstore --size=128M ...and create a small namespace that will register with the pstore sub-system. On the kernel side this would involve registering a 'pstore_dev' child / seed device under each region device. The 'seed-device' sysfs scheme is described in our documentation [1]. The short summary is ndctl finds a seed device assigns a namespace to it and then binding that device to a driver causes it to be initialized by the kernel. [1]: https://www.kernel.org/doc/Documentation/nvdimm/nvdimm.txt