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List:       qemu-devel
Subject:    [Qemu-devel] [PATCH 0/7] Qemu virtio pmem device
From:       Pankaj Gupta <pagupta () redhat ! com>
Date:       2019-05-23 10:36:42
Message-ID: 20190523102449.2642-1-pagupta () redhat ! com
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 This patch series has implementation for "virtio pmem"
 device. "virtio pmem" is persistent memory(nvdimm) device in
 guest which allows to bypass the guest page cache. This
 also implements a VIRTIO based asynchronous flush mechanism.
 Details of project idea for 'virtio pmem' flushing interface
 is shared [2] & [3].

 Sharing Qemu device emulation in this patchset. Tested with
 guest kernel driver [1]. This series is based on David's
 memory device refactoring [5] work with modified version of
 my initial virtio pmem [4] series.

 Usage:
 ./qemu -name test -machine pc -m 8G,slots$0,maxmem G
 -object memory-backend-file,id=mem1,share,mem-path=test.img,
  size=4G,share
 -device virtio-pmem-pci,memdev=mem1,id=nv1

 (qemu) info memory-devices
  Memory device [virtio-pmem]: "nv1"
  memaddr: 0x240000000
  size: 4294967296
  memdev: /objects/mem1

 Implementation is divided into two parts:
 New virtio pmem guest driver and qemu code changes for new
 virtio pmem paravirtualized device. In this series we are
 sharing Qemu device emulation.

1. Guest virtio-pmem kernel driver
---------------------------------
   - Reads persistent memory range from paravirt device and
     registers with 'nvdimm_bus'.
   - 'nvdimm/pmem' driver uses this information to allocate
     persistent memory region and setup filesystem operations
     to the allocated memory.
   - virtio pmem driver implements asynchronous flushing
     interface to flush from guest to host.

2. Qemu virtio-pmem device
---------------------------------
   - Creates virtio pmem device and exposes a memory range to
     KVM guest.
   - At host side this is file backed memory which acts as
     persistent memory.
   - Qemu side flush uses aio thread pool API's and virtio
     for asynchronous guest multi request handling.

 Virtio-pmem security implications and suggested countermeasures:
 ---------------------------------------------------------------

 In previous posting of kernel driver, there was discussion [7]
 on possible implications of page cache side channel attacks with
 virtio pmem. After thorough analysis of details of known side
 channel attacks, below are the suggestions:

 - Depends entirely on how host backing image file is mapped
   into guest address space.

 - virtio-pmem device emulation, by default shared mapping is used
   to map host backing file. It is recommended to use separate
   backing file at host side for every guest. This will prevent
   any possibility of executing common code from multiple guests
   and any chance of inferring guest local data based based on
   execution time.

 - If backing file is required to be shared among multiple guests
   it is recommended to don't support host page cache eviction
   commands from the guest driver. This will avoid any possibility
   of inferring guest local data or host data from another guest.

 - Proposed device specification [6] for virtio-pmem device with
   details of possible security implications and suggested
   countermeasures for device emulation.

[1] https://lkml.org/lkml/2019/5/21/569
[2] https://www.spinics.net/lists/kvm/msg149761.html
[3] https://www.spinics.net/lists/kvm/msg153095.html
[4] https://marc.info/?l=linux-kernel&m3572228719237&w=2
[5] https://marc.info/?l=qemu-devel&m3555721901824&w=2
[6] https://lists.oasis-open.org/archives/virtio-dev/201903/msg00083.html
[7] https://lkml.org/lkml/2019/1/9/1191

 Pankaj Gupta (3):
  virtio-pmem: add virtio device
  virtio-pmem: sync linux headers
  virtio-pci: proxy for virtio-pmem

 David Hildenbrand (4):
  virtio-pci: Allow to specify additional interfaces for the base type
  hmp: Handle virtio-pmem when printing memory device infos
  numa: Handle virtio-pmem in NUMA stats
  pc: Support for virtio-pmem-pci

 hmp.c                                        |   27 ++-
 hw/i386/Kconfig                              |    1
 hw/i386/pc.c                                 |   72 ++++++++++
 hw/virtio/Kconfig                            |   10 +
 hw/virtio/Makefile.objs                      |    2
 hw/virtio/virtio-pci.c                       |    1
 hw/virtio/virtio-pci.h                       |    1
 hw/virtio/virtio-pmem-pci.c                  |  131 ++++++++++++++++++
 hw/virtio/virtio-pmem-pci.h                  |   34 ++++
 hw/virtio/virtio-pmem.c                      |  190 +++++++++++++++++++++++++++
 include/hw/pci/pci.h                         |    1
 include/hw/virtio/virtio-pmem.h              |   49 ++++++
 include/standard-headers/linux/virtio_ids.h  |    1
 include/standard-headers/linux/virtio_pmem.h |   35 ++++
 numa.c                                       |   24 +--
 qapi/misc.json                               |   28 +++
 16 files changed, 581 insertions(+), 26 deletions(-)
----

 P.S: Sending this patch series before going for vacations, please
 expect a delay in response.


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