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

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Date:   Wed, 25 Apr 2018 10:55:57 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Eric Blake <eblake@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        qemu-devel@...gnu.org, linux-nvdimm@...1.01.org,
        linux-mm@...ck.org, kwolf@...hat.com,
        haozhong zhang <haozhong.zhang@...el.com>, jack@...e.cz,
        xiaoguangrong eric <xiaoguangrong.eric@...il.com>,
        riel@...riel.com, niteshnarayanlal@...mail.com, david@...hat.com,
        ross zwisler <ross.zwisler@...el.com>, lcapitulino@...hat.com,
        hch@...radead.org, mst@...hat.com, stefanha@...hat.com,
        pbonzini@...hat.com, marcel@...hat.com, imammedo@...hat.com,
        dan j williams <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'.

I see.

Thanks!
> 
> 
> > +++ 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.

o.k

> 
> > +              '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
> 
>