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Subject[RFC v3 0/2] kvm "fake DAX" device flushing
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 [2] & [3].

Pankaj Gupta (2):
Add virtio-pmem guest driver
pmem: device flush over VIRTIO


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(-)

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