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

[Pankaj Gupta <pagupta@redhat.com>]

> 
> On Wed, Jun 19, 2019 at 03:19:00PM +0530, Pankaj Gupta wrote:
> > 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
> >
> 
> Hi, Pankaj

Hi Wei,

> 
> I tried this series with v14 kernel driver, while getting some error on using
> this. Not sure this is my error configuration.
> 
> The qemu command line is:
> 
>     -object
>     memory-backend-file,id=mem1,share=on,mem-path=/dev/dax0.0,size=1G,align=2M
>     -device virtio-pmem-pci,memdev=mem1,id=nv1

Are you using host backing on real NVDIMM? Currently, we only support backing image 
file on regular SSD. We have plans to support backing file on real NVDIMM device
as well but this is part of future work.

Can you please try by allocating a raw image file on regular SSD. It is working fine
for me.

> 
> The guest boots up and I can see /dev/pmem0 device. But when I want to
> partition this device, I got the error:
> 
>     # parted /dev/pmem0 mklabel gpt
>     Warning: Error fsyncing/closing /dev/pmem0: Input/output error
> 
> Also I see an error when running "ndctl list":
> 
>     libndctl: __sysfs_device_parse: ndctl0: add_dev() failed

Will look at this if it is related.

Thanks,
Pankaj
> 
> Would you mind letting me know which part I am wrong?
> 
> > (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(-)
> >----
> 
> --
> Wei Yang
> Help you, Help me
> 
>