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Date:   Thu, 21 Mar 2019 10:21:40 -0600
From:   Keith Busch <kbusch@kernel.org>
To:     Stefan Hajnoczi <stefanha@redhat.com>
Cc:     Maxim Levitsky <mlevitsk@redhat.com>, Fam Zheng <fam@euphon.net>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Wolfram Sang <wsa@the-dreams.de>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Keith Busch <keith.busch@intel.com>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "Paul E . McKenney" <paulmck@linux.ibm.com>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        "Harris, James R" <james.r.harris@intel.com>,
        Felipe Franciosi <felipe@nutanix.com>,
        Liang Cunming <cunming.liang@intel.com>,
        Jens Axboe <axboe@fb.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Thanos Makatos <thanos.makatos@nutanix.com>,
        John Ferlan <jferlan@redhat.com>,
        Liu Changpeng <changpeng.liu@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Amnon Ilan <ailan@redhat.com>,
        "David S . Miller" <davem@davemloft.net>
Subject: Re: 
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On Thu, Mar 21, 2019 at 04:12:39PM +0000, Stefan Hajnoczi wrote:
> mdev-nvme seems like a duplication of SPDK.  The performance is not
> better and the features are more limited, so why focus on this approach?
> 
> One argument might be that the kernel NVMe subsystem wants to offer this
> functionality and loading the kernel module is more convenient than
> managing SPDK to some users.
> 
> Thoughts?

Doesn't SPDK bind a controller to a single process? mdev binds to
namespaces (or their partitions), so you could have many mdev's assigned
to many VMs accessing a single controller.