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From: Pankaj Gupta <pagupta@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org
Cc: jack@suse.cz, stefanha@redhat.com, dan.j.williams@intel.com,
	riel@surriel.com, haozhong.zhang@intel.com, nilal@redhat.com,
	kwolf@redhat.com, pbonzini@redhat.com, ross.zwisler@intel.com,
	david@redhat.com, xiaoguangrong.eric@gmail.com,
	hch@infradead.org, marcel@redhat.com, mst@redhat.com,
	niteshnarayanlal@hotmail.com, imammedo@redhat.com,
Subject: [RFC 0/2] kvm "fake DAX" device flushing
Date: Thu,  5 Apr 2018 16:18:31 +0530	[thread overview]
Message-ID: <20180405104834.10457-1-pagupta@redhat.com> (raw)

We are sharing RFC version of 'fake DAX' flushing
interface for feedback. This is still work in progress
and not yet ready for merging.

Prototype implements two major parts:

- Qemu virtio-pmem device
  It exposes a persistent memory range to KVM guest which at host side is file
  backed memory and works as persistent memory device. In addition to this it
  provides a virtio flushing interface for KVM guest to do a Qemu side sync for
  guest DAX persistent memory range.  

- Guest virtio-pmem driver
  Reads persistent memory range from paravirt device and registers with 'nvdimm_bus'.
  'nvdimm/pmem' driver uses this information to allocate persistent memory range. 
  Also, we have implemented guest side of VIRTIO flushing interface.
Changes from previous RFC:

- Reuse existing 'pmem' code instead of creating an entirely new block driver.
- Use VIRTIO driver to register memory information with nvdimm_bus and create
  region_type accordingly. 
- Use VIRTIO flushing interface from existing pmem driver code based on
  registered flushign mechanism.

We have done the implementation based on suggestions here [1]. Previous RFC is
shared here [2]. Details of project idea for 'fake DAX' flushing is shared 
here [3] & [4].

[1] https://marc.info/?l=linux-mm&m=150782346802290&w=2
[2] https://marc.info/?l=kvm&m=151630416506527&w=2
[3] https://www.spinics.net/lists/kvm/msg149761.html
[4] https://www.spinics.net/lists/kvm/msg153095.html

Work yet to be done:

- Qemu RAM address handling independent of PC-DIMM so that memory
  operations(get_free_address) can be used for VIRTIO device type as well. 
  (David Hildenbrand CCed has a prototype for this).
- Qemu device flush functionality trigger with guest fsync on file.
- Qemu live migration work when host page cache is used.
- Multiple virtio-pmem disks support.
- Prepare virtio spec after we get feedback on current approach.

 drivers/nvdimm/region_devs.c     |    7 ++
 drivers/virtio/Kconfig           |   12 +++
 drivers/virtio/Makefile          |    1 
 drivers/virtio/virtio_pmem.c     |  122 +++++++++++++++++++++++++++++++++++++++
 include/linux/libnvdimm.h        |    2 
 include/uapi/linux/virtio_ids.h  |    1 
 include/uapi/linux/virtio_pmem.h |   61 +++++++++++++++++++
 7 files changed, 206 insertions(+)

             reply	other threads:[~2018-04-05 10:48 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-05 10:48 Pankaj Gupta [this message]
     [not found] ` <20180405104834.10457-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-05 10:48   ` [RFC 1/2] kvm: add virtio pmem driver Pankaj Gupta
2018-04-05 10:48   ` [RFC 2/2] pmem: device flush over VIRTIO Pankaj Gupta
2018-04-05 10:48   ` [RFC] qemu: Add virtio pmem device Pankaj Gupta
     [not found]     ` <20180405104834.10457-4-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-05 11:26       ` David Hildenbrand
     [not found]         ` <ad08ca09-71ee-08d5-3479-8b3d06380a03-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-05 12:09           ` [Qemu-devel] " Pankaj Gupta
     [not found]             ` <416823501.16310251.1522930166070.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-05 12:19               ` David Hildenbrand
2018-04-09  3:26             ` Stefan Hajnoczi
     [not found]               ` <20180409032601.GA1648-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
2018-04-09  6:42                 ` David Hildenbrand
  -- strict thread matches above, loose matches on Subject: below --
2017-10-12 15:50 [RFC 0/2] KVM "fake DAX" device flushing Pankaj Gupta

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