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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Fri, 1 Feb 2019 21:26:25 -0800
Message-ID: <CAPcyv4g6mC09QZoPVbvuFuccovc-umdxHePXkKM2UQPo51gnZg@mail.gmail.com>
Subject: Re: [PATCH v2] nfit: add Hyper-V NVDIMM DSM command set to white list
To:     Dexuan Cui <decui@microsoft.com>
Cc:     Josh Poulson <jopoulso@microsoft.com>,
        "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "driverdev-devel@linuxdriverproject.org" 
        <driverdev-devel@linuxdriverproject.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Michael Kelley <mikelley@microsoft.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        Ross Zwisler <zwisler@kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>, Len Brown <lenb@kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Fri, Feb 1, 2019 at 7:32 PM Dexuan Cui <decui@microsoft.com> wrote:
>
> > From: Dan Williams <dan.j.williams@intel.com>
> > Sent: Friday, February 1, 2019 5:29 PM
> > ...
> > Honestly, the quickest path to something functional for Linux is to
> > simply delete the _LSR support and use raw mode defined namespaces.
> > Why have labels if they are read-only and the region is sufficient for
> > defining boundaries?
> Hyper-V Virtual NVDIMM can already work with Ubuntu 19.04 virtual machine
> running on Hyper-V, i.e. I can create a raw or fsdax namesapce, and create a
> xfs or ext4 file sysetm in /dev/pmem0p1, and mount the file system with and
> without "-o dax". The basic functionality is good.

Only in label-less mode apparently.

> My recent work is mainly for ndctl support, i.e. get the health info by ndctl,
> and use ndctl to monitor the error events (if applicable).

Right, but the recent fixes have exposed Linux to a labelled namespace
implementation that violates some of the driver's basic assumptions.

To preserve the level of operation you're currently seeing Linux might
need to add a hyper-v-specific quirk to force label-less operation.