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.
> >
> 
> I created a file with 2G on my disk.
> 
> #ll -h 2G-file
> -rw-r--r-- 1 richard richard 2.0G 6月  26 09:26 2G-file
> 
> The command line is changed to:
> 
>     -object
>     memory-backend-file,id=mem1,share,mem-path=/home/richard/guest/2G-file,size=2G
>     -device virtio-pmem-pci,memdev=mem1,id=nv1
> 
> The behavior in guest is the same.

Are you still facing an error with this? or its working fine for you?

> 
> I took a look into the directory /sys/bus/nd/device. These files are listed.
> Compared with normal system, one device file is missed.

virtio pmem does not support namespace/region mappings which ACPI NFIT supports.

> 
> btt0.0  dax0.0  namespace0.0  ndbus0  pfn0.0  region0
> 
> But the sysfs shows pmem0 block device is created.
> 
> /sys/devices/pci0000:00/0000:00:04.0/virtio0/ndbus0/region0/namespace0.0/block/pmem0
> 
> Then I took a look into the pci device:
> 
> # lspci -vs 00:04.0
> 00:04.0 Unclassified device [00ff]: Red Hat, Inc. Device 1013
>         Subsystem: Red Hat, Inc. Device 001b
>         Physical Slot: 4
>         Flags: bus master, fast devsel, latency 0, IRQ 11
>         I/O ports at c040 [size=64]
>         Memory at fe000000 (64-bit, prefetchable) [size=16K]
>         Capabilities: [84] Vendor Specific Information: VirtIO: 
>         Capabilities: [70] Vendor Specific Information: VirtIO: Notify
>         Capabilities: [60] Vendor Specific Information: VirtIO: DeviceCfg
>         Capabilities: [50] Vendor Specific Information: VirtIO: ISR
>         Capabilities: [40] Vendor Specific Information: VirtIO: CommonCfg
>         Kernel driver in use: virtio-pci
> 
> This looks good.

Good to know.

> 
> >> 
> >> 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.
> 
> This log still there.

It looks to me libndctl needs to be taught about about virtio pmem
data parsing. But this is unrelated to kernel and qemu patch series.

> 
> >
> >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
> >> 
> >> 
> 
> --
> Wei Yang
> Help you, Help me
> 
>