Re: [RFC v3 0/2] kvm "fake DAX" device flushing
From: David Hildenbrand
Date: Tue Aug 28 2018 - 08:13:38 EST
On 13.07.2018 09:52, Pankaj Gupta wrote:
> This is RFC V3 for 'fake DAX' flushing interface sharing
> for review. This patchset has two parts:
> - Guest virtio-pmem driver
> Guest driver reads persistent memory range from paravirt device
> and registers with 'nvdimm_bus'. 'nvdimm/pmem' driver uses this
> information to allocate persistent memory range. Also, we have
> implemented guest side of VIRTIO flushing interface.
> - Qemu virtio-pmem device
> It exposes a persistent memory range to KVM guest which at host
> side is file backed memory and works as persistent memory device.
> In addition to this it provides virtio device handling of flushing
> interface. KVM guest performs Qemu side asynchronous sync using
> this interface.
> Changes from RFC v2:
> - Add flush function in the nd_region in place of switching
> on a flag - Dan & Stefan
> - Add flush completion function with proper locking and wait
> for host side flush completion - Stefan & Dan
> - Keep userspace API in uapi header file - Stefan, MST
> - Use LE fields & New device id - MST
> - Indentation & spacing suggestions - MST & Eric
> - Remove extra header files & add licensing - Stefan
> Changes from RFC v1:
> - Reuse existing 'pmem' code for registering persistent
> memory and other operations instead of creating an entirely
> new block driver.
> - Use VIRTIO driver to register memory information with
> nvdimm_bus and create region_type accordingly.
> - Call VIRTIO flush from existing pmem driver.
> Details of project idea for 'fake DAX' flushing interface is
> shared  & .
> Pankaj Gupta (2):
> Add virtio-pmem guest driver
> pmem: device flush over VIRTIO
>  https://marc.info/?l=linux-mm&m=150782346802290&w=2
>  https://www.spinics.net/lists/kvm/msg149761.html
>  https://www.spinics.net/lists/kvm/msg153095.html
> drivers/nvdimm/nd.h | 1
> drivers/nvdimm/pmem.c | 4
> drivers/nvdimm/region_devs.c | 24 +++-
> drivers/virtio/Kconfig | 9 +
> drivers/virtio/Makefile | 1
> drivers/virtio/virtio_pmem.c | 190 +++++++++++++++++++++++++++++++++++++++
> include/linux/libnvdimm.h | 5 -
> include/linux/virtio_pmem.h | 44 +++++++++
> include/uapi/linux/virtio_ids.h | 1
> include/uapi/linux/virtio_pmem.h | 40 ++++++++
> 10 files changed, 310 insertions(+), 9 deletions(-)
do you have a branch for the QEMU part somewhere available? I want to
see how this works with MemoryDevice changes.
David / dhildenb