linux-kernel - Re: [Linux-nvdimm] another pmem variant

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Message-ID: <20150325170430.GA2223@lst.de>
Date:	Wed, 25 Mar 2015 18:04:30 +0100
From:	Christoph Hellwig <hch@....de>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Christoph Hellwig <hch@....de>,
	linux-nvdimm <linux-nvdimm@...1.01.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Jens Axboe <axboe@...nel.dk>
Subject: Re: [Linux-nvdimm] another pmem variant

On Wed, Mar 25, 2015 at 10:00:26AM -0700, Dan Williams wrote:
> The kernel command line would simply be the standard/existing memmap=
> to reserve a memory range.  Then, when the platform device loads, it
> does a request_firmware() to inject a binary table that further carves
> memory into ranges to which the pmem driver attaches.  No need for the
> legacy system BIOS to be upgraded to the "new way".

Ewww...

> It does do the right thing in kernel space.  The userspace utility
> creates the binary table (once) that can be compiled into the platform
> device driver or auto-loaded by an initrd.  The problem with a new
> memmap= is that it is too coarse.  For example you can't do things
> like specify a pmem range per-NUMA node.

Sure you can as long as you know the layout.  memmap= can be specified
multiple times.   Again, I see absolutely zero benefit of doing crap
like request_firmware() to convert interface, and I'm also tired of
having this talk about code that will eventually be released and should
be superior (and from all that I can guess so far will actually be far
worse).
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