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

[Wei Yang <richardw.yang@linux.intel.com>]

On Tue, Jul 02, 2019 at 09:31:43PM -0400, Pankaj Gupta wrote:
>
>> >
>> >> 
>> >> 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 can partition and mkfs with /dev/pmem0 after I use the SSD backend.

>> 
>> 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.
>

Ok, thanks.

>> 
>> 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.
>

Ok, if it works, we could list those regions? and change pmem0 mode to dax
mode, right?

>> 
>> >
>> >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
>> 
>> 

-- 
Wei Yang
Help you, Help me