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Subject[PATCH 0/8] Introduce a device-dax bus-based device-model
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Prompted by the review of "[PATCH 0/9] Allow persistent memory to be
used like normal RAM" [1] introduce a new bus / device-driver-model
for device-dax.

Currently device-dax instances result from attaching an nvdimm namespace
device to the dax_pmem driver. These instances are registered with the
/sys/class/dax sub-system. With the expectation that platforms will
describe performance differentiated memory [2] for ranges other than
persistent memory (pmem) a new device-model is needed.

Arrange for dax_pmem to be one of potentially several drivers that know
how to discover differentiated memory and register a device instance on
the dax bus. The expectation is that, by default, this device is
consumed by the typical device-dax driver that will expose the range
through a /dev/daxX.Y character device. Optionally other drivers can
consume the dax device instance. For example, the kmem driver [1] can
attach to device-dax device instance to hot-add the related memory range
to the core page-allocator.

Going forward, provider drivers outside of dax_pmem can be created to
register other memories with unique performance properties.

Since /sys/class/dax is a released ABI, a compat driver is provided so
that distros can opt-in to the new bus based ABI. The /sys/class/dax
interface is then deprecated and scheduled to be removed.

[1]: https://lkml.org/lkml/2018/10/23/9
[2]: Section 5.2.27 Heterogeneous Memory Attribute Table (HMAT)
http://www.uefi.org/sites/default/files/resources/ACPI%206_2_A_Sept29.pdf

---

Dan Williams (8):
device-dax: Kill dax_region ida
device-dax: Kill dax_region base
device-dax: Remove multi-resource infrastructure
device-dax: Start defining a dax bus model
device-dax: Introduce bus + driver model
device-dax: Move resource pinning+mapping into the common driver
device-dax: Add support for a dax override driver
device-dax: Add /sys/class/dax backwards compatibility


Documentation/ABI/obsolete/sysfs-class-dax | 22 +
drivers/dax/Kconfig | 12 +
drivers/dax/Makefile | 5
drivers/dax/bus.c | 449 ++++++++++++++++++++++++++++
drivers/dax/bus.h | 60 ++++
drivers/dax/dax-private.h | 30 +-
drivers/dax/dax.h | 18 -
drivers/dax/device-dax.h | 25 --
drivers/dax/device.c | 365 +++++------------------
drivers/dax/pmem.c | 161 ----------
drivers/dax/pmem/Makefile | 7
drivers/dax/pmem/compat.c | 73 +++++
drivers/dax/pmem/core.c | 69 ++++
drivers/dax/pmem/pmem.c | 40 ++
drivers/dax/super.c | 41 ++-
tools/testing/nvdimm/Kbuild | 7
tools/testing/nvdimm/dax-dev.c | 16 -
17 files changed, 880 insertions(+), 520 deletions(-)
create mode 100644 Documentation/ABI/obsolete/sysfs-class-dax
create mode 100644 drivers/dax/bus.c
create mode 100644 drivers/dax/bus.h
delete mode 100644 drivers/dax/dax.h
delete mode 100644 drivers/dax/device-dax.h
delete mode 100644 drivers/dax/pmem.c
create mode 100644 drivers/dax/pmem/Makefile
create mode 100644 drivers/dax/pmem/compat.c
create mode 100644 drivers/dax/pmem/core.c
create mode 100644 drivers/dax/pmem/pmem.c

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