linux-kernel - Re: [Qemu-devel] [RFC v2] qemu: Add virtio pmem device

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Message-ID: <25f3e433-cfa6-4a62-ba7f-47aef1119dfc@redhat.com>
Date:   Wed, 25 Apr 2018 09:25:37 -0500
From:   Eric Blake <eblake@...hat.com>
To:     Pankaj Gupta <pagupta@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, qemu-devel@...gnu.org,
        linux-nvdimm@...1.01.org, linux-mm@...ck.org
Cc:     kwolf@...hat.com, haozhong.zhang@...el.com, jack@...e.cz,
        xiaoguangrong.eric@...il.com, riel@...riel.com,
        niteshnarayanlal@...mail.com, david@...hat.com,
        ross.zwisler@...el.com, lcapitulino@...hat.com, hch@...radead.org,
        mst@...hat.com, stefanha@...hat.com, imammedo@...hat.com,
        marcel@...hat.com, pbonzini@...hat.com, dan.j.williams@...el.com,
        nilal@...hat.com
Subject: Re: [Qemu-devel] [RFC v2] qemu: Add virtio pmem device

On 04/25/2018 06:24 AM, Pankaj Gupta wrote:
> This patch adds virtio-pmem Qemu device.
> 
> This device presents memory address range 
> information to guest which is backed by file 
> backend type. It acts like persistent memory 
> device for KVM guest. Guest can perform read 
> and persistent write operations on this memory 
> range with the help of DAX capable filesystem.
> 
> Persistent guest writes are assured with the 
> help of virtio based flushing interface. When 
> guest userspace space performs fsync on file 
> fd on pmem device, a flush command is send to 
> Qemu over VIRTIO and host side flush/sync is 
> done on backing image file.
> 
> This PV device code is dependent and tested 
> with 'David Hildenbrand's ' patchset[1] to 
> map non-PCDIMM devices to guest address space.

This sentence doesn't belong in git history.  It is better to put
information like this...

> There is still upstream discussion on using 
> among PCI bar vs memory device, will update 
> as per concensus.

s/concensus/consensus/

> 
> [1] https://marc.info/?l=qemu-devel&m=152450249319168&w=2
> 
> Signed-off-by: Pankaj Gupta <pagupta@...hat.com>
> ---

...here, where it is part of the email, but not picked up by 'git am'.


> +++ b/qapi/misc.json
> @@ -2871,6 +2871,29 @@
>            }
>  }
>  
> +##
> +# @VirtioPMemDeviceInfo:
> +#
> +# VirtioPMem state information
> +#
> +# @id: device's ID
> +#
> +# @start: physical address, where device is mapped
> +#
> +# @size: size of memory that the device provides
> +#
> +# @memdev: memory backend linked with device
> +#
> +# Since: 2.13
> +##
> +{ 'struct': 'VirtioPMemDeviceInfo',
> +    'data': { '*id': 'str',
> +	      'start': 'size',
> +	      'size': 'size',

TAB damage.

> +              'memdev': 'str'
> +	    }
> +}
> +
>  ##
>  # @MemoryDeviceInfo:
>  #
> @@ -2880,7 +2903,8 @@
>  ##
>  { 'union': 'MemoryDeviceInfo',
>    'data': { 'dimm': 'PCDIMMDeviceInfo',
> -            'nvdimm': 'PCDIMMDeviceInfo'
> +            'nvdimm': 'PCDIMMDeviceInfo',
> +	    'virtio-pmem': 'VirtioPMemDeviceInfo'
>            }
>  }
>  
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org



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