Create a kernel documentation to describe how the CXL shared upstream
link bandwidth is calculated.
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Link: https://patch.msgid.link/20240904001316.1688225-4-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
New Changes:
- Refactor to a common struct for DRAM and general media CXL events
- Add abstract distance calculation support for CXL
- Add CXL maturity map documentation to detail current state of CXL enabling
- Add warning on mixed CXL VH and RCH/RCD hierachy to inform unsupported config
- Replace ENXIO with EBUSY for inject poison limit reached via debugfs
- Replace ENXIO with EBUSY for inject poison cxl-test support
- XOR math fixup for DPA to SPA translation. Current math works for MODULO arithmetic
where HPA==SPA, however not for XOR decode.
- Move pci config read in cxl_dvsec_rr_decode() to avoid unnecessary acess
Fixes:
- Add a fix to address race condition in CXL memory hotplug notifier
- Add missing MODULE_DESCRIPTION() for CXL modules
- Fix incorrect vendor debug UUID define
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Merge tag 'cxl-for-6.11' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl
Pull CXL updates from Dave Jiang:
"Core:
- A CXL maturity map has been added to the documentation to detail
the current state of CXL enabling.
It provides the status of the current state of various CXL features
to inform current and future contributors of where things are and
which areas need contribution.
- A notifier handler has been added in order for a newly created CXL
memory region to trigger the abstract distance metrics calculation.
This should bring parity for CXL memory to the same level vs
hotplugged DRAM for NUMA abstract distance calculation. The
abstract distance reflects relative performance used for memory
tiering handling.
- An addition for XOR math has been added to address the CXL DPA to
SPA translation.
CXL address translation did not support address interleave math
with XOR prior to this change.
Fixes:
- Fix to address race condition in the CXL memory hotplug notifier
- Add missing MODULE_DESCRIPTION() for CXL modules
- Fix incorrect vendor debug UUID define
Misc:
- A warning has been added to inform users of an unsupported
configuration when mixing CXL VH and RCH/RCD hierarchies
- The ENXIO error code has been replaced with EBUSY for inject poison
limit reached via debugfs and cxl-test support
- Moving the PCI config read in cxl_dvsec_rr_decode() to avoid
unnecessary PCI config reads
- A refactor to a common struct for DRAM and general media CXL
events"
* tag 'cxl-for-6.11' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl:
cxl/core/pci: Move reading of control register to immediately before usage
cxl: Remove defunct code calculating host bridge target positions
cxl/region: Verify target positions using the ordered target list
cxl: Restore XOR'd position bits during address translation
cxl/core: Fold cxl_trace_hpa() into cxl_dpa_to_hpa()
cxl/test: Replace ENXIO with EBUSY for inject poison limit reached
cxl/memdev: Replace ENXIO with EBUSY for inject poison limit reached
cxl/acpi: Warn on mixed CXL VH and RCH/RCD Hierarchy
cxl/core: Fix incorrect vendor debug UUID define
Documentation: CXL Maturity Map
cxl/region: Simplify cxl_region_nid()
cxl/region: Support to calculate memory tier abstract distance
cxl/region: Fix a race condition in memory hotplug notifier
cxl: add missing MODULE_DESCRIPTION() macros
cxl/events: Use a common struct for DRAM and General Media events
Provide a survey of the work-in-progress maturity (implementation
status) of various aspects of the CXL subsystem.
Clarify that in addition to ongoing upkeep relative to specification
updates, there are some long running themes in the driver that respond
to the discovery of new corner cases (bugs) and new use cases (feature
extensions).
The primary audience is distribution maintainers, but it also serves as
a guide for kernel developers to understand what aspects of the CXL
subsystem need more help. It is a landing page to document ongoing
progress, and a guide to discern exposure to work-in-progress features.
Reviewed-by: Adam Manzanares <a.manzanares@samsung.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/172005486862.2048248.6668794717827294862.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Add the missing files into cxl driver api and fix the compile warning.
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Yao Xingtao <yaoxt.fnst@fujitsu.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://patch.msgid.link/20240614084755.59503-3-yaoxt.fnst@fujitsu.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Sphinx reported kernel-doc failure warning, pointing to non-existent
drivers/cxl/region.h (which doesn't also exist throughout repo history):
WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 2.4.4 -no-doc-sections ./drivers/cxl/region.h' failed with return code 1
Above cause error message to be displayed on htmldocs output.
Delete the reference.
Fixes: 779dd20cfb ("cxl/region: Add region creation support")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20220804075448.98241-4-bagasdotme@gmail.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
CXL 2.0 allows for dynamic provisioning of new memory regions (system
physical address resources like "System RAM" and "Persistent Memory").
Whereas DDR and PMEM resources are conveyed statically at boot, CXL
allows for assembling and instantiating new regions from the available
capacity of CXL memory expanders in the system.
Sysfs with an "echo $region_name > $create_region_attribute" interface
is chosen as the mechanism to initiate the provisioning process. This
was chosen over ioctl() and netlink() to keep the configuration
interface entirely in a pseudo-fs interface, and it was chosen over
configfs since, aside from this one creation event, the interface is
read-mostly. I.e. configfs supports cases where an object is designed to
be provisioned each boot, like an iSCSI storage target, and CXL region
creation is mostly for PMEM regions which are created usually once
per-lifetime of a server instance. This is an improvement over nvdimm
that pre-created "seed" devices that tended to confuse users looking to
determine which devices are active and which are idle.
Recall that the major change that CXL brings over previous persistent
memory architectures is the ability to dynamically define new regions.
Compare that to drivers like 'nfit' where the region configuration is
statically defined by platform firmware.
Regions are created as a child of a root decoder that encompasses an
address space with constraints. When created through sysfs, the root
decoder is explicit. When created from an LSA's region structure a root
decoder will possibly need to be inferred by the driver.
Upon region creation through sysfs, a vacant region is created with a
unique name. Regions have a number of attributes that must be configured
before the region can be bound to the driver where HDM decoder program
is completed.
An example of creating a new region:
- Allocate a new region name:
region=$(cat /sys/bus/cxl/devices/decoder0.0/create_pmem_region)
- Create a new region by name:
while
region=$(cat /sys/bus/cxl/devices/decoder0.0/create_pmem_region)
! echo $region > /sys/bus/cxl/devices/decoder0.0/create_pmem_region
do true; done
- Region now exists in sysfs:
stat -t /sys/bus/cxl/devices/decoder0.0/$region
- Delete the region, and name:
echo $region > /sys/bus/cxl/devices/decoder0.0/delete_region
Signed-off-by: Ben Widawsky <bwidawsk@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/165784333909.1758207.794374602146306032.stgit@dwillia2-xfh.jf.intel.com
[djbw: simplify locking, reword changelog]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
At this point the subsystem can enumerate all CXL ports (CXL.mem decode
resources in upstream switch ports and host bridges) in a system. The
last mile is connecting those ports to endpoints.
The cxl_mem driver connects an endpoint device to the platform CXL.mem
protoctol decode-topology. At ->probe() time it walks its
device-topology-ancestry and adds a CXL Port object at every Upstream
Port hop until it gets to CXL root. The CXL root object is only present
after a platform firmware driver registers platform CXL resources. For
ACPI based platform this is managed by the ACPI0017 device and the
cxl_acpi driver.
The ports are registered such that disabling a given port automatically
unregisters all descendant ports, and the chain can only be registered
after the root is established.
Given ACPI device scanning may run asynchronously compared to PCI device
scanning the root driver is tasked with rescanning the bus after the
root successfully probes.
Conversely if any ports in a chain between the root and an endpoint
becomes disconnected it subsequently triggers the endpoint to
unregister. Given lock depenedencies the endpoint unregistration happens
in a workqueue asynchronously. If userspace cares about synchronizing
delayed work after port events the /sys/bus/cxl/flush attribute is
available for that purpose.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
[djbw: clarify changelog, rework hotplug support]
Link: https://lore.kernel.org/r/164398782997.903003.9725273241627693186.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The need for a CXL port driver and a dedicated cxl_bus_type is driven by
a need to simultaneously support 2 independent physical memory decode
domains (cache coherent CXL.mem and uncached PCI.mmio) that also
intersect at a single PCIe device node. A CXL Port is a device that
advertises a CXL Component Register block with an "HDM Decoder
Capability Structure".
>From Documentation/driver-api/cxl/memory-devices.rst:
Similar to how a RAID driver takes disk objects and assembles them into
a new logical device, the CXL subsystem is tasked to take PCIe and ACPI
objects and assemble them into a CXL.mem decode topology. The need for
runtime configuration of the CXL.mem topology is also similar to RAID in
that different environments with the same hardware configuration may
decide to assemble the topology in contrasting ways. One may choose
performance (RAID0) striping memory across multiple Host Bridges and
endpoints while another may opt for fault tolerance and disable any
striping in the CXL.mem topology.
The port driver identifies whether an endpoint Memory Expander is
connected to a CXL topology. If an active (bound to the 'cxl_port'
driver) CXL Port is not found at every PCIe Switch Upstream port and an
active "root" CXL Port then the device is just a plain PCIe endpoint
only capable of participating in PCI.mmio and DMA cycles, not CXL.mem
coherent interleave sets.
The 'cxl_port' driver lets the CXL subsystem leverage driver-core
infrastructure for setup and teardown of register resources and
communicating device activation status to userspace. The cxl_bus_type
can rendezvous the async arrival of platform level CXL resources (via
the 'cxl_acpi' driver) with the asynchronous enumeration of Memory
Expander endpoints, while also implementing a hierarchical locking model
independent of the associated 'struct pci_dev' locking model. The
locking for dport and decoder enumeration is now handled in the core
rather than callers.
For now the port driver only enumerates and registers CXL resources
(downstream port metadata and decoder resources) later it will be used
to take action on its decoders in response to CXL.mem region
provisioning requests.
Note1: cxlpci.h has long depended on pci.h, but port.c was the first to
not include pci.h. Carry that dependency in cxlpci.h.
Note2: cxl port enumeration and probing complicates CXL subsystem init
to the point that it helps to have centralized debug logging of probe
events in cxl_bus_probe().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/164374948116.464348.1772618057599155408.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Kernel docs are already present in this file, but nothing is instructed
to generate them. Address that.
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Link: https://lore.kernel.org/r/20210913163324.1008564-2-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Now that the internals of mailbox operations are abstracted from the PCI
specifics a bulk of infrastructure can move to the core.
The CXL_PMEM driver intends to proxy LIBNVDIMM UAPI and driver requests
to the equivalent functionality provided by the CXL hardware mailbox
interface. In support of that intent move the mailbox implementation to
a shared location for the CXL_PCI driver native IOCTL path and CXL_PMEM
nvdimm command proxy path to share.
A unit test framework seeks to implement a unit test backend transport
for mailbox commands to communicate mocked up payloads. It can reuse all
of the mailbox infrastructure minus the PCI specifics, so that also gets
moved to the core.
Finally with the mailbox infrastructure and ioctl handling being
transport generic there is no longer any need to pass file
file_operations to devm_cxl_add_memdev(). That allows all the ioctl
boilerplate to move into the core for unit test reuse.
No functional change intended, just code movement.
Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/163116435233.2460985.16197340449713287180.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The register mapping infrastructure is large enough to move to its own
compilation unit. This also cleans up an unnecessary include of <mem.h>
core/bus.c.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162800068975.665205.12895551621746585289.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Refactor the pmem / nvdimm-bridge functionality from core/bus.c to
core/pmem.c. Introduce drivers/core/core.h to communicate data
structures and helpers between the core bus and other functionality that
registers devices on the bus.
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162792538899.368511.3881663908293411300.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
CXL core is growing, and it's already arguably unmanageable. To support
future growth, move core functionality to a new directory and rename the
file to represent just bus support. Future work will remove non-bus
functionality.
Note that mem.h is renamed to cxlmem.h to avoid a namespace collision
with the global ARCH=um mem.h header.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162792537866.368511.8915631504621088321.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
While CXL builds upon the PCI software model for enumeration and
endpoint control, a static platform component is required to bootstrap
the CXL memory layout. Similar to how ACPI identifies root-level PCI
memory resources, ACPI data enumerates the address space and interleave
configuration for CXL Memory.
In addition to identifying host bridges, ACPI is responsible for
enumerating the CXL memory space that can be addressed by downstream
decoders. This is similar to the requirement for ACPI to publish
resources via the _CRS method for PCI host bridges. Specifically, ACPI
publishes a table, CXL Early Discovery Table (CEDT), which includes a
list of CXL Memory resources, CXL Fixed Memory Window Structures
(CFMWS).
For now, introduce the core infrastructure for a cxl_port hierarchy
starting with a root level anchor represented by the ACPI0017 device.
Follow on changes model support for the configurable decode capabilities
of cxl_port instances, i.e. CXL switch support.
Co-developed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162325449515.2293126.15303270193010154608.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
As the driver has undergone development, it's become clear that the
majority [entirety?] of the current functionality in mem.c is actually a
layer encapsulating functionality exposed through PCI based
interactions. This layer can be used either in isolation or to provide
functionality for higher level functionality.
CXL capabilities exist in a parallel domain to PCIe. CXL devices are
enumerable and controllable via "legacy" PCIe mechanisms; however, their
CXL capabilities are a superset of PCIe. For example, a CXL device may
be connected to a non-CXL capable PCIe root port, and therefore will not
be able to participate in CXL.mem or CXL.cache operations, but can still
be accessed through PCIe mechanisms for CXL.io operations.
To properly represent the PCI nature of this driver, and in preparation for
introducing a new driver for the CXL.mem / HDM decoder (Host-managed Device
Memory) capabilities of a CXL memory expander, rename mem.c to pci.c so that
mem.c is available for this new driver.
The result of the change is that there is a clear layering distinction
in the driver, and a systems administrator may load only the cxl_pci
module and gain access to such operations as, firmware update, offline
provisioning of devices, and error collection. In addition to freeing up
the file name for another purpose, there are two primary reasons this is
useful,
1. Acting upon devices which don't have full CXL capabilities. This
may happen for instance if the CXL device is connected in a CXL
unaware part of the platform topology.
2. Userspace-first provisioning for devices without kernel driver
interference. This may be useful when provisioning a new device
in a specific manner that might otherwise be blocked or prevented
by the real CXL mem driver.
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Link: https://lore.kernel.org/r/20210526174413.802913-1-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
In preparation for more generic shared functionality across endpoint
consumers of core cxl resources, and platform-firmware producers of
those resources, rename bus.c to core.c. In addition to the central
rendezvous for interleave coordination, the core will also define common
routines like CXL register block mapping.
Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162096972018.1865304.11079951161445408423.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Add a straightforward IOCTL that provides a mechanism for userspace to
query the supported memory device commands. CXL commands as they appear
to userspace are described as part of the UAPI kerneldoc. The command
list returned via this IOCTL will contain the full set of commands that
the driver supports, however, some of those commands may not be
available for use by userspace.
Memory device commands first appear in the CXL 2.0 specification. They
are submitted through a mailbox mechanism specified in the CXL 2.0
specification.
The send command allows userspace to issue mailbox commands directly to
the hardware. The list of available commands to send are the output of
the query command. The driver verifies basic properties of the command
and possibly inspect the input (or output) payload to determine whether
or not the command is allowed (or might taint the kernel).
Reported-by: kernel test robot <lkp@intel.com> # bug in earlier revision
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2)
Cc: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20210217040958.1354670-5-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Create the /sys/bus/cxl hierarchy to enumerate:
* Memory Devices (per-endpoint control devices)
* Memory Address Space Devices (platform address ranges with
interleaving, performance, and persistence attributes)
* Memory Regions (active provisioned memory from an address space device
that is in use as System RAM or delegated to libnvdimm as Persistent
Memory regions).
For now, only the per-endpoint control devices are registered on the
'cxl' bus. However, going forward it will provide a mechanism to
coordinate cross-device interleave.
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> (v2)
Link: https://lore.kernel.org/r/20210217040958.1354670-4-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Provide enough functionality to utilize the mailbox of a memory device.
The mailbox is used to interact with the firmware running on the memory
device. The flow is proven with one implemented command, "identify".
Because the class code has already told the driver this is a memory
device and the identify command is mandatory.
CXL devices contain an array of capabilities that describe the
interactions software can have with the device or firmware running on
the device. A CXL compliant device must implement the device status and
the mailbox capability. Additionally, a CXL compliant memory device must
implement the memory device capability. Each of the capabilities can
[will] provide an offset within the MMIO region for interacting with the
CXL device.
The capabilities tell the driver how to find and map the register space
for CXL Memory Devices. The registers are required to utilize the CXL
spec defined mailbox interface. The spec outlines two mailboxes, primary
and secondary. The secondary mailbox is earmarked for system firmware,
and not handled in this driver.
Primary mailboxes are capable of generating an interrupt when submitting
a background command. That implementation is saved for a later time.
Reported-by: Colin Ian King <colin.king@canonical.com> (coverity)
Reported-by: Dan Carpenter <dan.carpenter@oracle.com> (smatch)
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2)
Link: https://www.computeexpresslink.org/download-the-specification
Link: https://lore.kernel.org/r/20210217040958.1354670-3-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The CXL.mem protocol allows a device to act as a provider of "System
RAM" and/or "Persistent Memory" that is fully coherent as if the memory
was attached to the typical CPU memory controller.
With the CXL-2.0 specification a PCI endpoint can implement a "Type-3"
device interface and give the operating system control over "Host
Managed Device Memory". See section 2.3 Type 3 CXL Device.
The memory range exported by the device may optionally be described by
the platform firmware memory map, or by infrastructure like LIBNVDIMM to
provision persistent memory capacity from one, or more, CXL.mem devices.
A pre-requisite for Linux-managed memory-capacity provisioning is this
cxl_mem driver that can speak the mailbox protocol defined in section
8.2.8.4 Mailbox Registers.
For now just land the initial driver boiler-plate and Documentation/
infrastructure.
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: David Rientjes <rientjes@google.com> (v1)
Cc: Jonathan Corbet <corbet@lwn.net>
Link: https://www.computeexpresslink.org/download-the-specification
Link: https://lore.kernel.org/r/20210217040958.1354670-2-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
