linux-kernel - Re: [PATCH v6 07/21] libnvdimm, nfit: regions (block-data-window, persistent memory, volatile memory)

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Date:	Thu, 18 Jun 2015 00:03:50 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	linux-nvdimm@...ts.01.org, mingo@...nel.org, sfr@...b.auug.org.au,
	rafael@...nel.org, neilb@...e.de, gregkh@...uxfoundation.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	jmoyer@...hat.com, axboe@...nel.dk, linux-api@...r.kernel.org,
	akpm@...ux-foundation.org, hch@....de
Subject: Re: [PATCH v6 07/21] libnvdimm, nfit: regions (block-data-window, persistent memory, volatile memory)

On Thursday, June 11, 2015 04:10:47 PM Dan Williams wrote:
> A "region" device represents the maximum capacity of a BLK range (mmio
> block-data-window(s)), or a PMEM range (DAX-capable persistent memory or
> volatile memory), without regard for aliasing.  Aliasing, in the
> dimm-local address space (DPA), is resolved by metadata on a dimm to
> designate which exclusive interface will access the aliased DPA ranges.
> Support for the per-dimm metadata/label arrvies is in a subsequent
> patch.
> 
> The name format of "region" devices is "regionN" where, like dimms, N is
> a global ida index assigned at discovery time.  This id is not reliable
> across reboots nor in the presence of hotplug.  Look to attributes of
> the region or static id-data of the sub-namespace to generate a
> persistent name.  However, if the platform configuration does not change
> it is reasonable to expect the same region id to be assigned at the next
> boot.
> 
> "region"s have 2 generic attributes "size", and "mapping"s where:
> - size: the BLK accessible capacity or the span of the
>   system physical address range in the case of PMEM.
> 
> - mappingN: a tuple describing a dimm's contribution to the region's
>   capacity in the format (<nmemX>,<dpa>,<size>).  For a PMEM-region
>   there will be at least one mapping per dimm in the interleave set.  For
>   a BLK-region there is only "mapping0" listing the starting DPA of the
>   BLK-region and the available DPA capacity of that space (matches "size"
>   above).
> 
> The max number of mappings per "region" is hard coded per the
> constraints of sysfs attribute groups.  That said the number of mappings
> per region should never exceed the maximum number of possible dimms in
> the system.  If the current number turns out to not be enough then the
> "mappings" attribute clarifies how many there are supposed to be. "32
> should be enough for anybody...".
> 
> Cc: Neil Brown <neilb@...e.de>
> Cc: <linux-acpi@...r.kernel.org>
> Cc: Greg KH <gregkh@...uxfoundation.org>
> Cc: Robert Moore <robert.moore@...el.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

For the ACPI part:

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

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