| 059edcc4 | 27-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Parent dax_hmem devices
For test purposes it is useful to be able to determine which
"hmem_platform" device is hosting a given sub-device.
Register hmem devices underneath "hmem_platform"
dax/hmem: Parent dax_hmem devices
For test purposes it is useful to be able to determine which
"hmem_platform" device is hosting a given sub-device.
Register hmem devices underneath "hmem_platform".
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260327052821.440749-8-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
show more ...
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| f8dc1bde | 27-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Fix singleton confusion between dax_hmem_work and hmem devices
dax_hmem (ab)uses a platform device to allow for a module to autoload in
the presence of "Soft Reserved" resources. The dax_h
dax/hmem: Fix singleton confusion between dax_hmem_work and hmem devices
dax_hmem (ab)uses a platform device to allow for a module to autoload in
the presence of "Soft Reserved" resources. The dax_hmem driver had no
dependencies on the "hmem_platform" device being a singleton until the
recent "dax_hmem vs dax_cxl" takeover solution.
Replace the layering violation of dax_hmem_work assuming that there will
never be more than one "hmem_platform" device associated with a global work
item with a dax_hmem local workqueue that can theoretically support any
number of hmem_platform devices.
Fixup the reference counting to only pin the device while it is live in the
queue.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260327052821.440749-7-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| 3cba30ee | 27-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Reduce visibility of dax_cxl coordination symbols
No other module or use case should be using dax_hmem_initial_probe or
dax_hmem_flush_work(). Limit their use to dax_hmem, and dax_cxl
resp
dax/hmem: Reduce visibility of dax_cxl coordination symbols
No other module or use case should be using dax_hmem_initial_probe or
dax_hmem_flush_work(). Limit their use to dax_hmem, and dax_cxl
respectively.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260327052821.440749-6-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| 471d8844 | 27-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
cxl/region: Constify cxl_region_resource_contains()
The call to cxl_region_resource_contains() in hmem_register_cxl_device()
need not cast away 'const'. The problem is the usage of the
bus_for_each_
cxl/region: Constify cxl_region_resource_contains()
The call to cxl_region_resource_contains() in hmem_register_cxl_device()
need not cast away 'const'. The problem is the usage of the
bus_for_each_dev() API which does not mark its @data parameter as 'const'.
Switch to bus_find_device() which does take 'const' @data, fixup
cxl_region_resource_contains() and its caller.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260327052821.440749-5-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| b6a61d5b | 27-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
cxl/region: Limit visibility of cxl_region_contains_resource()
The dax_hmem dependency on cxl_region_contains_resource() is a one-off
special case. It is not suitable for other use cases.
Move the
cxl/region: Limit visibility of cxl_region_contains_resource()
The dax_hmem dependency on cxl_region_contains_resource() is a one-off
special case. It is not suitable for other use cases.
Move the definition to the other CONFIG_CXL_REGION guarded definitions in
drivers/cxl/cxl.h and include that by a relative path include. This matches
what drivers/dax/cxl.c does for its limited private usage of CXL core
symbols.
Reduce the symbol export visibility from global to just dax_hmem, to
further clarify its applicability.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260327052821.440749-4-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| e4de6b91 | 22-Mar-2026 |
Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> |
dax/hmem, cxl: Defer and resolve Soft Reserved ownership
The current probe time ownership check for Soft Reserved memory based
solely on CXL window intersection is insufficient. dax_hmem probing is
dax/hmem, cxl: Defer and resolve Soft Reserved ownership
The current probe time ownership check for Soft Reserved memory based
solely on CXL window intersection is insufficient. dax_hmem probing is not
always guaranteed to run after CXL enumeration and region assembly, which
can lead to incorrect ownership decisions before the CXL stack has
finished publishing windows and assembling committed regions.
Introduce deferred ownership handling for Soft Reserved ranges that
intersect CXL windows. When such a range is encountered during the
initial dax_hmem probe, schedule deferred work to wait for the CXL stack
to complete enumeration and region assembly before deciding ownership.
Once the deferred work runs, evaluate each Soft Reserved range
individually: if a CXL region fully contains the range, skip it and let
dax_cxl bind. Otherwise, register it with dax_hmem. This per-range
ownership model avoids the need for CXL region teardown and
alloc_dax_region() resource exclusion prevents double claiming.
Introduce a boolean flag dax_hmem_initial_probe to live inside device.c
so it survives module reload. Ensure dax_cxl defers driver registration
until dax_hmem has completed ownership resolution. dax_cxl calls
dax_hmem_flush_work() before cxl_driver_register(), which both waits for
the deferred work to complete and creates a module symbol dependency that
forces dax_hmem.ko to load before dax_cxl.
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260322195343.206900-9-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| edfcf1e2 | 22-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Gate Soft Reserved deferral on DEV_DAX_CXL
Replace IS_ENABLED(CONFIG_CXL_REGION) with IS_ENABLED(CONFIG_DEV_DAX_CXL)
so that HMEM only defers Soft Reserved ranges when CXL DAX support is
e
dax/hmem: Gate Soft Reserved deferral on DEV_DAX_CXL
Replace IS_ENABLED(CONFIG_CXL_REGION) with IS_ENABLED(CONFIG_DEV_DAX_CXL)
so that HMEM only defers Soft Reserved ranges when CXL DAX support is
enabled. This makes the coordination between HMEM and the CXL stack more
precise and prevents deferral in unrelated CXL configurations.
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260322195343.206900-5-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| 7b4bcaad | 22-Mar-2026 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Request cxl_acpi and cxl_pci before walking Soft Reserved ranges
Ensure cxl_acpi has published CXL Window resources before HMEM walks Soft
Reserved ranges.
Replace MODULE_SOFTDEP("pre: cx
dax/hmem: Request cxl_acpi and cxl_pci before walking Soft Reserved ranges
Ensure cxl_acpi has published CXL Window resources before HMEM walks Soft
Reserved ranges.
Replace MODULE_SOFTDEP("pre: cxl_acpi") with an explicit, synchronous
request_module("cxl_acpi"). MODULE_SOFTDEP() only guarantees eventual
loading, it does not enforce that the dependency has finished init
before the current module runs. This can cause HMEM to start before
cxl_acpi has populated the resource tree, breaking detection of overlaps
between Soft Reserved and CXL Windows.
Also, request cxl_pci before HMEM walks Soft Reserved ranges. Unlike
cxl_acpi, cxl_pci attach is asynchronous and creates dependent devices
that trigger further module loads. Asynchronous probe flushing
(wait_for_device_probe()) is added later in the series in a deferred
context before HMEM makes ownership decisions for Soft Reserved ranges.
Add an additional explicit Kconfig ordering so that CXL_ACPI and CXL_PCI
must be initialized before DEV_DAX_HMEM. This prevents HMEM from consuming
Soft Reserved ranges before CXL drivers have had a chance to claim them.
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Tomasz Wolski <tomasz.wolski@fujitsu.com>
Link: https://patch.msgid.link/20260322195343.206900-4-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
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| 09d09e04 | 10-Feb-2023 |
Dan Williams <dan.j.williams@intel.com> |
cxl/dax: Create dax devices for CXL RAM regions
While platform firmware takes some responsibility for mapping the RAM
capacity of CXL devices present at boot, the OS is responsible for
mapping the r
cxl/dax: Create dax devices for CXL RAM regions
While platform firmware takes some responsibility for mapping the RAM
capacity of CXL devices present at boot, the OS is responsible for
mapping the remainder and hot-added devices. Platform firmware is also
responsible for identifying the platform general purpose memory pool,
typically DDR attached DRAM, and arranging for the remainder to be 'Soft
Reserved'. That reservation allows the CXL subsystem to route the memory
to core-mm via memory-hotplug (dax_kmem), or leave it for dedicated
access (device-dax).
The new 'struct cxl_dax_region' object allows for a CXL memory resource
(region) to be published, but also allow for udev and module policy to
act on that event. It also prevents cxl_core.ko from having a module
loading dependency on any drivers/dax/ modules.
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/167602003896.1924368.10335442077318970468.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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| e9ee9fe3 | 10-Feb-2023 |
Dan Williams <dan.j.williams@intel.com> |
dax: Assign RAM regions to memory-hotplug by default
The default mode for device-dax instances is backwards for RAM-regions
as evidenced by the fact that it tends to catch end users by surprise.
"Wh
dax: Assign RAM regions to memory-hotplug by default
The default mode for device-dax instances is backwards for RAM-regions
as evidenced by the fact that it tends to catch end users by surprise.
"Where is my memory?". Recall that platforms are increasingly shipping
with performance-differentiated memory pools beyond typical DRAM and
NUMA effects. This includes HBM (high-bandwidth-memory) and CXL (dynamic
interleave, varied media types, and future fabric attached
possibilities).
For this reason the EFI_MEMORY_SP (EFI Special Purpose Memory => Linux
'Soft Reserved') attribute is expected to be applied to all memory-pools
that are not the general purpose pool. This designation gives an
Operating System a chance to defer usage of a memory pool until later in
the boot process where its performance properties can be interrogated
and administrator policy can be applied.
'Soft Reserved' memory can be anything from too limited and precious to
be part of the general purpose pool (HBM), too slow to host hot kernel
data structures (some PMEM media), or anything in between. However, in
the absence of an explicit policy, the memory should at least be made
usable by default. The current device-dax default hides all
non-general-purpose memory behind a device interface.
The expectation is that the distribution of users that want the memory
online by default vs device-dedicated-access by default follows the
Pareto principle. A small number of enlightened users may want to do
userspace memory management through a device, but general users just
want the kernel to make the memory available with an option to get more
advanced later.
Arrange for all device-dax instances not backed by PMEM to default to
attaching to the dax_kmem driver. From there the baseline memory hotplug
policy (CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE / memhp_default_state=)
gates whether the memory comes online or stays offline. Where, if it
stays offline, it can be reliably converted back to device-mode where it
can be partitioned, or fronted by a userspace allocator.
So, if someone wants device-dax instances for their 'Soft Reserved'
memory:
1/ Build a kernel with CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=n or boot
with memhp_default_state=offline, or roll the dice and hope that the
kernel has not pinned a page in that memory before step 2.
2/ Write a udev rule to convert the target dax device(s) from
'system-ram' mode to 'devdax' mode:
daxctl reconfigure-device $dax -m devdax -f
Cc: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Gregory Price <gregory.price@memverge.com>
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/167602003336.1924368.6809503401422267885.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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| 7dab174e | 10-Feb-2023 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Move hmem device registration to dax_hmem.ko
In preparation for the CXL region driver to take over the responsibility
of registering device-dax instances for CXL regions, move the
registra
dax/hmem: Move hmem device registration to dax_hmem.ko
In preparation for the CXL region driver to take over the responsibility
of registering device-dax instances for CXL regions, move the
registration of "hmem" devices to dax_hmem.ko.
Previously the builtin component of this enabling
(drivers/dax/hmem/device.o) would register platform devices for each
address range and trigger the dax_hmem.ko module to load and attach
device-dax instances to those devices. Now, the ranges are collected
from the HMAT and EFI memory map walking, but the device creation is
deferred. A new "hmem_platform" device is created which triggers
dax_hmem.ko to load and register the platform devices.
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/167602002771.1924368.5653558226424530127.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
show more ...
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| fe098574 | 10-Feb-2023 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Convey the dax range via memregion_info()
In preparation for hmem platform devices to be unregistered, stop using
platform_device_add_resources() to convey the address range. The
platform_
dax/hmem: Convey the dax range via memregion_info()
In preparation for hmem platform devices to be unregistered, stop using
platform_device_add_resources() to convey the address range. The
platform_device_add_resources() API causes an existing "Soft Reserved"
iomem resource to be re-parented under an inserted platform device
resource. When that platform device is deleted it removes the platform
device resource and all children.
Instead, it is sufficient to convey just the address range and let
request_mem_region() insert resources to indicate the devices active in
the range. This allows the "Soft Reserved" resource to be re-enumerated
upon the next probe event.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/167602002217.1924368.7036275892522551624.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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| 84fe17f8 | 10-Feb-2023 |
Dan Williams <dan.j.williams@intel.com> |
dax/hmem: Drop unnecessary dax_hmem_remove()
Empty driver remove callbacks can just be elided.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Gregory Price <gregory.price@
dax/hmem: Drop unnecessary dax_hmem_remove()
Empty driver remove callbacks can just be elided.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Gregory Price <gregory.price@memverge.com>
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/167602001664.1924368.9102029637928071240.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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| 5a505603 | 14-Oct-2020 |
Joao Martins <joao.m.martins@oracle.com> |
dax/hmem: introduce dax_hmem.region_idle parameter
Introduce a new module parameter for dax_hmem which initializes all region
devices as free, rather than allocating a pagemap for the region by
defa
dax/hmem: introduce dax_hmem.region_idle parameter
Introduce a new module parameter for dax_hmem which initializes all region
devices as free, rather than allocating a pagemap for the region by
default.
All hmem devices created with dax_hmem.region_idle=1 will have full
available size for creating dynamic dax devices.
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hulk Robot <hulkci@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jason Yan <yanaijie@huawei.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Jia He <justin.he@arm.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/159643106460.4062302.5868522341307530091.stgit@dwillia2-desk3.amr.corp.intel.com
Link: https://lore.kernel.org/r/20200716172913.19658-4-joao.m.martins@oracle.com
Link: https://lkml.kernel.org/r/160106119033.30709.11249962152222193448.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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