Re: [Qemu-devel] [PATCH v2 0/7] Qemu virtio pmem device

[Pankaj Gupta]

Ping.

> 
> 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=240,maxmem=20G
>  -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.
> 
> Changes from PATCH v1:
>  - Change proposed version from qemu 4.0 to 4.1 - Eric
>  - Remove virtio queue_add from unrealize function - Cornelia
> 
> [1] https://lkml.org/lkml/2019/6/12/624
> [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&m=153572228719237&w=2
> [5] https://marc.info/?l=qemu-devel&m=153555721901824&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                      |  189
>  +++++++++++++++++++++++++++
>  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, 580 insertions(+), 26 deletions(-)
> ----
> 
>