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Subject: Re: [PATCH v2 06/10] nvme/core: add mdev interfaces
To:     Christoph Hellwig <hch@infradead.org>,
        Maxim Levitsky <mlevitsk@redhat.com>
CC:     Fam Zheng <fam@euphon.net>, <kvm@vger.kernel.org>,
        Wolfram Sang <wsa@the-dreams.de>,
        <linux-nvme@lists.infradead.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>,
        "Liang Cunming" <cunming.liang@intel.com>,
        Jens Axboe <axboe@fb.com>,
        "Alex Williamson" <alex.williamson@redhat.com>,
        John Ferlan <jferlan@redhat.com>,
        Liu Changpeng <changpeng.liu@intel.com>,
        Jens Axboe <axboe@kernel.dk>,
        "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>
References: <20190502114801.23116-1-mlevitsk@redhat.com>
 <20190502114801.23116-7-mlevitsk@redhat.com>
 <20190503122902.GA5081@infradead.org>
From:   Max Gurtovoy <maxg@mellanox.com>
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Date:   Fri, 3 May 2019 22:00:54 +0300
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On 5/3/2019 3:29 PM, Christoph Hellwig wrote:
> On Thu, May 02, 2019 at 02:47:57PM +0300, Maxim Levitsky wrote:
>> If the mdev device driver also sets the
>> NVME_F_MDEV_DMA_SUPPORTED, the mdev core will
>> dma map all the guest memory into the nvme device,
>> so that nvme device driver can use dma addresses as passed
>> from the mdev core driver
> We really need a proper block layer interface for that so that
> uring or the nvme target can use pre-mapping as well.

I think we can also find a way to use nvme-mdev for the target offload 
p2p feature.

Don't see a big difference of taking NVMe queue and namespace/partition 
to guest OS or to P2P since IO is issued by external entity and pooled 
outside the pci driver.

thoughts ?


>
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