linux-kernel - Re: [PATCH RFC 10/10] nvdimm/e820: add multiple namespaces support

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Message-ID: <CAPcyv4iiSsEOsfEwLQcV3bNDjBSxw1OgWoBdEWPQEymq6=xm-A@mail.gmail.com>
Date:   Tue, 4 Feb 2020 08:44:31 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Barret Rhoden <brho@...gle.com>
Cc:     Joao Martins <joao.m.martins@...cle.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        KVM list <kvm@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Liran Alon <liran.alon@...cle.com>,
        Nikita Leshenko <nikita.leshchenko@...cle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH RFC 10/10] nvdimm/e820: add multiple namespaces support

On Tue, Feb 4, 2020 at 7:30 AM Barret Rhoden <brho@...gle.com> wrote:
>
> Hi -
>
> On 1/10/20 2:03 PM, Joao Martins wrote:
> > User can define regions with 'memmap=size!offset' which in turn
> > creates PMEM legacy devices. But because it is a label-less
> > NVDIMM device we only have one namespace for the whole device.
> >
> > Add support for multiple namespaces by adding ndctl control
> > support, and exposing a minimal set of features:
> > (ND_CMD_GET_CONFIG_SIZE, ND_CMD_GET_CONFIG_DATA,
> > ND_CMD_SET_CONFIG_DATA) alongside NDD_ALIASING because we can
> > store labels.
>
> FWIW, I like this a lot.  If we move away from using memmap in favor of
> efi_fake_mem, ideally we'd have the same support for full-fledged
> pmem/dax regions and namespaces that this patch brings.

No, efi_fake_mem only supports creating dax-regions. What's the use
case that can't be satisfied by just specifying multiple memmap=
ranges?