linux-kernel - Re: [Linux-nvdimm] [PATCH 04/21] nd: create an 'nd_bus' from an 'nfit

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Date:	Tue, 21 Apr 2015 13:35:46 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-nvdimm] [PATCH 04/21] nd: create an 'nd_bus' from an 'nfit_desc'

On Tue, Apr 21, 2015 at 12:55 PM, Toshi Kani <toshi.kani@...com> wrote:
> On Tue, 2015-04-21 at 12:58 -0700, Dan Williams wrote:
>> On Tue, Apr 21, 2015 at 12:35 PM, Toshi Kani <toshi.kani@...com> wrote:
>> > On Fri, 2015-04-17 at 21:35 -0400, Dan Williams wrote:
>> >  :
>> >> +
>> >> +static int nd_mem_init(struct nd_bus *nd_bus)
>> >> +{
>> >> +     struct nd_spa *nd_spa;
>> >> +
>> >> +     /*
>> >> +      * For each SPA-DCR address range find its corresponding
>> >> +      * MEMDEV(s).  From each MEMDEV find the corresponding DCR.
>> >> +      * Then, try to find a SPA-BDW and a corresponding BDW that
>> >> +      * references the DCR.  Throw it all into an nd_mem object.
>> >> +      * Note, that BDWs are optional.
>> >> +      */
>> >> +     list_for_each_entry(nd_spa, &nd_bus->spas, list) {
>> >> +             u16 spa_index = readw(&nd_spa->nfit_spa->spa_index);
>> >> +             int type = nfit_spa_type(nd_spa->nfit_spa);
>> >> +             struct nd_mem *nd_mem, *found;
>> >> +             struct nd_memdev *nd_memdev;
>> >> +             u16 dcr_index;
>> >> +
>> >> +             if (type != NFIT_SPA_DCR)
>> >> +                     continue;
>> >
>> > This function requires NFIT_SPA_DCR, SPA Range Structure with NVDIMM
>> > Control Region GUID, for initializing an nd_mem object.  However,
>> > battery-backed DIMMs do not have such control region SPA.  IIUC, the
>> > NFIT spec does not require NFIT_SPA_DCR.
>> >
>> > Can you change this function to work with NFIT_SPA_PM as well?
>>
>> NFIT_SPA_PM ranges are handled separately from nd_mem_init().  See
>> nd_region_create() in patch 10.
>
> If nd_mem_init() does not initialize nd_mem objects, nd_bus_probe() in
> core.c fails in nd_bus_init_interleave_sets() and skips all subsequent
> nd_bus_xxx() calls.  So, nd_region_create() won't be called.
>
> nd_bus_init_interleave_sets() fails because init_interleave_set()
> returns -ENODEV if (!nd_mem).

Ah, ok  your test case is specifying PMEM backed by memory device
info.  We have a test case for simple ranges (nfit_test1_setup()), but
it doesn't hit this bug because it does not specify any memory-device
tables.

Thanks, will fix this in v2 of the patch set.

> BTW, there are two nd_bus_probe() in bus.c and core.c, which is
> confusing.

Ok, will fix this as well in the v2 posting.
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