- Jul 26, 2022
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Dan Williams authored
After all the soft validation of the region has completed, convey the region configuration to hardware while being careful to commit decoders in specification mandated order. In addition to programming the endpoint decoder base-address, interleave ways and granularity, the switch decoder target lists are also established. While the kernel can enforce spec-mandated commit order, it can not enforce spec-mandated reset order. For example, the kernel can't stop someone from removing an endpoint device that is occupying decoderN in a switch decoder where decoderN+1 is also committed. To reset decoderN, decoderN+1 must be torn down first. That "tear down the world" implementation is saved for a follow-on patch. Callback operations are provided for the 'commit' and 'reset' operations. While those callbacks may prove useful for CXL accelerators (Type-2 devices with memory) the primary motivation is to enable a simple way for cxl_test to intercept those operations. Reviewed-by:
Jonathan Cameron <Jonathan.Cameron@huawei.com> Link: https://lore.kernel.org/r/165784338418.1758207.14659830845389904356.stgit@dwillia2-xfh.jf.intel.com Signed-off-by:
Dan Williams <dan.j.williams@intel.com>
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Dan Williams authored
Once the region's interleave geometry (ways, granularity, size) is established and all the endpoint decoder targets are assigned, the next phase is to program all the intermediate decoders. Specifically, each CXL switch in the path between the endpoint and its CXL host-bridge (including the logical switch internal to the host-bridge) needs to have its decoders programmed and the target list order assigned. The difficulty in this implementation lies in determining which endpoint decoder ordering combinations are valid. Consider the cxl_test case of 2 host bridges, each of those host-bridges attached to 2 switches, and each of those switches attached to 2 endpoints for a potential 8-way interleave. The x2 interleave at the host-bridge level requires that all even numbered endpoint decoder positions be located on the "left" hand side of the topology tree, and the odd numbered positions on the other. The endpoints that are peers on the same switch need to have a position that can be routed with a dedicated address bit per-endpoint. See check_last_peer() for the details. Reviewed-by:
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Dan Williams authored
CXL regions (interleave sets) are made up of a set of memory devices where each device maps a portion of the interleave with one of its decoders (see CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure). As endpoint decoders are identified by a provisioning tool they can be added to a region provided the region interleave properties are set (way, granularity, HPA) and DPA has been assigned to the decoder. The attach event triggers several validation checks, for example: - is the DPA sized appropriately for the region - is the decoder reachable via the host-bridges identified by the region's root decoder - is the device already active in a different region position slot - are there already regions with a higher HPA active on a given port (per CXL 2.0 8.2.5.12.20 Committing Decoder Programming) ...and the attach event affords an opportunity to collect data and resources relevant to later programming the target lists in switch decoders, for example: - allocate a decoder at each cxl_port in the decode chain - for a given switch port, how many the region's endpoints are hosted through the port - how many unique targets (next hops) does a port need to map to reach those endpoints The act of reconciling this information and deploying it to the decoder configuration is saved for a follow-on patch. Co-developed-by:
Ben Widawsky <bwidawsk@kernel.org> Signed-off-by:
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Dan Williams authored
The ACPI CXL Fixed Memory Window Structure (CFMWS) defines multiple methods to determine which host bridge provides access to a given endpoint relative to that device's position in the interleave. The "Interleave Arithmetic" defines either a "standard modulo" / round-random algorithm, or "xormap" based algorithm which can be defined as a non-linear transform. Given that there are already more options beyond "standard modulo" and that "xormap" may turn out to be ACPI CXL specific, provide a callback for the region provisioning code to map endpoint positions back to expected host bridge id (cxl_dport target). For now just support the simple modulo math case and save the xormap for a follow-on change. Reviewed-by:
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Dan Williams authored
The region provisioning process involves allocating DPA to a set of endpoint decoders, and HPA plus the region geometry to a region device. Then the decoder is assigned to the region. At this point several validation steps can be performed to validate that the decoder is suitable to participate in the region. Co-developed-by:
kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/r/165784336184.1758207.16403282029203949622.stgit@dwillia2-xfh.jf.intel.com Signed-off-by:
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Dan Williams authored
After a region's interleave parameters (ways and granularity) are set, add a way for regions to allocate HPA (host physical address space) from the free capacity in their parent root-decoder. The allocator for this capacity reuses the 'struct resource' based allocator used for CONFIG_DEVICE_PRIVATE. Once the tuple of "ways, granularity, [uuid], and size" is set the region configuration transitions to the CXL_CONFIG_INTERLEAVE_ACTIVE state which is a precursor to allowing endpoint decoders to be added to a region. Co-developed-by:
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Ben Widawsky authored
Add ABI to allow the number of devices that comprise a region to be set as well as the interleave granularity for the region. Signed-off-by:
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Ben Widawsky authored
The process of provisioning a region involves triggering the creation of a new region object, pouring in the configuration, and then binding that configured object to the region driver to start its operation. For persistent memory regions the CXL specification mandates that it identified by a uuid. Add an ABI for userspace to specify a region's uuid. Signed-off-by:
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- Jul 22, 2022
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Ben Widawsky authored
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:
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Dan Williams authored
The core of devm_request_free_mem_region() is a helper that searches for free space in iomem_resource and performs __request_region_locked() on the result of that search. The policy choices of the implementation conform to what CONFIG_DEVICE_PRIVATE users want which is memory that is immediately marked busy, and a preference to search for the first-fit free range in descending order from the top of the physical address space. CXL has a need for a similar allocator, but with the following tweaks: 1/ Search for free space in ascending order 2/ Search for free space relative to a given CXL window 3/ 'insert' rather than 'request' the new resource given downstream drivers from the CXL Region driver (like the pmem or dax drivers) are responsible for request_mem_region() when they activate the memory range. Rework __request_free_mem_region() into get_free_mem_region() which takes a set of GFR_* (Get Free Region) flags to control the allocation policy (ascending vs descending), and "busy" policy (insert_resource() vs request_region()). As part of the consolidation of the legacy GFR_REQUEST_REGION case with the new default of just inserting a new resource into the free space some minor cleanups like not checking for NULL before calling devres_free() (which does its own check) is included. Suggested-by:
Jason Gunthorpe <jgg@nvidia.com> Link: https://lore.kernel.org/linux-cxl/20220420143406.GY2120790@nvidia.com/ Cc: Matthew Wilcox <willy@infradead.org> Cc: Christoph Hellwig <hch@lst.de> Reviewed-by:
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Dan Williams authored
The port scanning algorithm in devm_cxl_enumerate_ports() walks up the topology and adds cxl_port objects starting from the root down to the endpoint. When those ports are initially created they know all their dports, but they do not know the downstream cxl_port instance that represents the next descendant in the topology. Rework create_endpoint() into devm_cxl_add_endpoint() that enumerates the downstream cxl_port topology into each port's 'struct cxl_ep' record for each endpoint it that the port is an ancestor. Reviewed-by:
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Ben Widawsky authored
The region provisioning flow involves selecting interleave ways + granularity settings for a region, and then programming the decoder topology to meet those constraints, if possible. For example, root decoders set the minimum interleave ways + granularity for any hosted regions. Given decoder programming is not atomic and collisions can occur between multiple requesting regions userspace will be responsible for conflict resolution and it needs these attributes to make those decisions. Signed-off-by:
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Dan Williams authored
Reduce the complexity and the overhead of walking the topology to determine endpoint connectivity to root decoder interleave configurations. Note that cxl_detach_ep(), after it determines that the last @ep has departed and decides to delete the port, now needs to walk the dport array with the device_lock() held to remove entries. Previously list_splice_init() could be used atomically delete all dport entries at once and then perform entry tear down outside the lock. There is no list_splice_init() equivalent for the xarray. Reviewed-by:
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Dan Williams authored
In preparation for region provisioning that needs to walk the topology by endpoints, use an xarray to record endpoint interest in a given port. In addition to being more space and time efficient it also reduces the complexity of the implementation by moving locking internal to the xarray implementation. It also allows for a single cxl_ep reference to be recorded in multiple xarrays. Reviewed-by:
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Dan Williams authored
At the time that cxl_port instances are being created, cache the dport from the parent port that points to this new child port. This will be useful for region provisioning when walking the tree to calculate decoder targets, and saves rewalking the dport list after the fact to build this information. Reviewed-by:
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Dan Williams authored
Recall that the primary role of the cxl_mem driver is to probe if the given endpoint is connected to a CXL port topology. In that process it walks its device ancestry to its PCI root port. If that root port is also a CXL root port then the probe process adds cxl_port object instances at switch in the path between to the root and the endpoint. As those cxl_port instances are added, or if a previous enumeration attempt already created the port, a 'struct cxl_ep' instance is registered with that port to track the endpoints interested in that port. At the time the cxl_ep is registered the downstream egress path from the port to the endpoint is known. Take the opportunity to record that information as it will be needed for dynamic programming of decoder targets during region provisioning. Reviewed-by:
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Dan Williams authored
The region provisioning flow will roughly follow a sequence of: 1/ Allocate DPA to a set of decoders 2/ Allocate HPA to a region 3/ Associate decoders with a region and validate that the DPA allocations and topologies match the parameters of the region. For now, this change (step 1) arranges for DPA capacity to be allocated and deleted from non-committed decoders based on the decoder's mode / partition selection. Capacity is allocated from the lowest DPA in the partition and any 'pmem' allocation blocks out all remaining ram capacity in its 'skip' setting. DPA allocations are enforced in decoder instance order. I.e. decoder N + 1 always starts at a higher DPA than instance N, and deleting allocations must proceed from the highest-instance allocated decoder to the lowest. Reviewed-by:
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Dan Williams authored
The CXL specification enforces that endpoint decoders are committed in hw instance id order. In preparation for adding dynamic DPA allocation, record the hw instance id in endpoint decoders, and enforce allocations to occur in hw instance id order. Reviewed-by:
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Dan Williams authored
Recall that the Device Physical Address (DPA) space of a CXL Memory Expander is potentially partitioned into a volatile and persistent portion. A decoder maps a Host Physical Address (HPA) range to a DPA range and that translation depends on the value of all previous (lower instance number) decoders before the current one. In preparation for allowing dynamic provisioning of regions, decoders need an ABI to indicate which DPA partition a decoder targets. This ABI needs to be prepared for the possibility that some other agent committed and locked a decoder that spans the partition boundary. Add 'decoderX.Y/mode' to endpoint decoders that indicates which partition 'ram' / 'pmem' the decoder targets, or 'mixed' if the decoder currently spans the partition boundary. Reviewed-by:
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Dan Williams authored
In preparation for provisioning CXL regions, add accounting for the DPA space consumed by existing regions / decoders. Recall, a CXL region is a memory range comprised from one or more endpoint devices contributing a mapping of their DPA into HPA space through a decoder. Record the DPA ranges covered by committed decoders at initial probe of endpoint ports relative to a per-device resource tree of the DPA type (pmem or volatile-ram). The cxl_dpa_rwsem semaphore is introduced to globally synchronize DPA state across all endpoints and their decoders at once. The vast majority of DPA operations are reads as region creation is expected to be as rare as disk partitioning and volume creation. The device_lock() for this synchronization is specifically avoided for concern of entangling with sysfs attribute removal. Co-developed-by:
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- Jul 21, 2022
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Dan Williams authored
Previously the target routing specifics of switch decoders and platform CXL window resource tracking of root decoders were factored out of 'struct cxl_decoder'. While switch decoders translate from SPA to downstream ports, endpoint decoders translate from SPA to DPA. This patch, 3 of 3, adds a 'struct cxl_endpoint_decoder' that tracks an endpoint-specific Device Physical Address (DPA) resource. For now this just defines ->dpa_res, a follow-on patch will handle requesting DPA resource ranges from a device-DPA resource tree. Co-developed-by:
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Dan Williams authored
Previously the target routing specifics of switch decoders were factored out of 'struct cxl_decoder' into 'struct cxl_switch_decoder'. This patch, 2 of 3, adds a 'struct cxl_root_decoder' as a superset of a switch decoder that also track the associated CXL window platform resource. Note that the reason the resource for a given root decoder needs to be looked up after the fact (i.e. after cxl_parse_cfmws() and add_cxl_resource()) is because add_cxl_resource() may have merged CXL windows in order to keep them at the top of the resource tree / decode hierarchy. Co-developed-by:
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Dan Williams authored
Recall that CXL capable address ranges, on ACPI platforms, are published in the CEDT.CFMWS (CXL Early Discovery Table: CXL Fixed Memory Window Structures). These windows represent both the actively mapped capacity and the potential address space that can be dynamically assigned to a new CXL decode configuration (region / interleave-set). CXL endpoints like DDR DIMMs can be mapped at any physical address including 0 and legacy ranges. There is an expectation and requirement that the /proc/iomem interface and the iomem_resource tree in the kernel reflect the full set of platform address ranges. I.e. that every address range that platform firmware and bus drivers enumerate be reflected as an iomem_resource entry. The hard requirement to do this for CXL arises from the fact that facilities like CONFIG_DEVICE_PRIVATE expect to be able to treat empty iomem_resource ranges as free for software to use as proxy address space. Without CXL publishing its potential address ranges in iomem_resource, the CONFIG_DEVICE_PRIVATE mechanism may inadvertently steal capacity reserved for runtime provisioning of new CXL regions. So, iomem_resource needs to know about both active and potential CXL resource ranges. The active CXL resources might already be reflected in iomem_resource as "System RAM". insert_resource_expand_to_fit() handles re-parenting "System RAM" underneath a CXL window. The "_expand_to_fit()" behavior handles cases where a CXL window is not a strict superset of an existing entry in the iomem_resource tree. The "_expand_to_fit()" behavior is acceptable from the perspective of resource allocation. The expansion happens because a conflicting resource range is already populated, which means the resource boundary expansion does not result in any additional free CXL address space being made available. CXL address space allocation is always bounded by the orginal unexpanded address range. However, the potential for expansion does mean that something like walk_iomem_res_desc(IORES_DESC_CXL...) can only return fuzzy answers on corner case platforms that cause the resource tree to expand a CXL window resource over a range that is not decoded by CXL. This would be an odd platform configuration, but if it becomes a problem in practice the CXL subsytem could just publish an API that returns definitive answers. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: David Hildenbrand <david@redhat.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Christoph Hellwig <hch@lst.de> Reviewed-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: https://lore.kernel.org/r/165784325943.1758207.5310344844375305118.stgit@dwillia2-xfh.jf.intel.com Signed-off-by:
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Dan Williams authored
Currently 'struct cxl_decoder' contains the superset of attributes needed for all decoder types. Before more type-specific attributes are added to the common definition, reorganize 'struct cxl_decoder' into type specific objects. This patch, the first of three, factors out a cxl_switch_decoder type. See the new kdoc for what a 'struct cxl_switch_decoder' represents in a CXL topology. Co-developed-by:
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- Jul 20, 2022
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Dan Williams authored
Make it easier to read delineations between the "Description" line break, new paragraph line breaks, and new entries. Reviewed-by:
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Ira Weiny authored
The per-device CDAT data provides performance data that is relevant for mapping which CXL devices can participate in which CXL ranges by QTG (QoS Throttling Group) (per ECN: CXL 2.0 CEDT CFMWS & QTG_DSM) [1]. The QTG association specified in the ECN is advisory. Until the cxl_acpi driver grows support for invoking the QTG _DSM method the CDAT data is only of interest to userspace that may need it for debug purposes. Search the DOE mailboxes available, query CDAT data, cache the data and make it available via a sysfs binary attribute per endpoint at: /sys/bus/cxl/devices/endpointX/CDAT ...similar to other ACPI-structured table data in /sys/firmware/ACPI/tables. The CDAT is relative to 'struct cxl_port' objects since switches in addition to endpoints can host a CDAT instance. Switch CDAT support is not implemented. This does not support table updates at runtime. It will always provide whatever was there when first cached. It is also the case that table updates are not expected outside of explicit DPA address map affecting commands like Set Partition with the immediate flag set. Given that the driver does not support Set Partition with the immediate flag set there is no current need for update support. Link: https://www.computeexpresslink.org/spec-landing [1] Signed-off-by:
Ira Weiny <ira.weiny@intel.com> [djbw: drop in-kernel parsing infra for now, and other minor fixups] Reviewed-by:
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Ira Weiny authored
Many binary attributes need to limit access to CAP_SYS_ADMIN only; ie many binary attributes specify is_visible with 0400 or 0600. Make setting the permissions of such attributes more explicit by defining BIN_ATTR_ADMIN_{RO,RW}. Cc: Bjorn Helgaas <bhelgaas@google.com> Suggested-by:Krzysztof Wilczyński <kw@linux.com> Reviewed-by:
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Ira Weiny authored
DOE mailbox objects will be needed for various mailbox communications with each memory device. Iterate each DOE mailbox capability and create PCI DOE mailbox objects as found. It is not anticipated that this is the final resting place for the iteration of the DOE devices. The support of switch ports will drive this code into the PCIe side. In this imagined architecture the CXL port driver would then query into the PCI device for the DOE mailbox array. For now creating the mailboxes in the CXL port is good enough for the endpoints. Later PCIe ports will need to support this to support switch ports more generically. Cc: Dan Williams <dan.j.williams@intel.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Lukas Wunner <lukas@wunner.de> Reviewed-by:
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Jonathan Cameron authored
Introduced in a PCIe r6.0, sec 6.30, DOE provides a config space based mailbox with standard protocol discovery. Each mailbox is accessed through a DOE Extended Capability. Each DOE mailbox must support the DOE discovery protocol in addition to any number of additional protocols. Define core PCIe functionality to manage a single PCIe DOE mailbox at a defined config space offset. Functionality includes iterating, creating, query of supported protocol, and task submission. Destruction of the mailboxes is device managed. Cc: "Li, Ming" <ming4.li@intel.com> Cc: Bjorn Helgaas <helgaas@kernel.org> Cc: Matthew Wilcox <willy@infradead.org> Acked-by:
Bjorn Helgaas <helgaas@kernel.org> Signed-off-by:
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Ira Weiny authored
Replace the magic value in pci_bus_crs_vendor_id() with PCI_VENDOR_ID_PCI_SIG. Reviewed-by:
Davidlohr Bueso <dave@stgolabs.net> Suggested-by:
Bjorn Helgaas <bhelgaas@google.com> Acked-by:
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Jonathan Cameron authored
This ID is used in DOE headers to identify protocols that are defined within the PCI Express Base Specification, PCIe r6.0, sec 6.30.1.1 table 6-32. Acked-by:
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- Jul 12, 2022
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Dan Williams authored
While there is a need to go from a LIBNVDIMM 'struct nvdimm' to a CXL 'struct cxl_nvdimm', there is no use case to go the other direction. Likely this is a leftover from an early version of the referenced commit before it implemented devm for releasing the created nvdimm. Reviewed-by:
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- Jul 11, 2022
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Dan Williams authored
Unless and until accelerator (type-2) drivers start registering for CXL.mem mapping services from the CXL subsystem core, initialize idle HDM decoders to the "expander" type. I.e. the only CXL devices using the CXL core presently are those implementing the CXL 2.0 Type-3 memory expander device class code that the cxl_pci driver claims. Reviewed-by:
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Dan Williams authored
Region creation has need for checking host-bridge connectivity when adding endpoints to regions. Record, at port creation time, the host-bridge to provide a useful shortcut from any location in the topology to the most-significant ancestor. Reviewed-by:
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Dan Williams authored
The 'enabled' state is reserved for committed decoders. By default, cxl_test decoders are uncommitted at init time. Fixes: 7c7d68db ("tools/testing/cxl: Enumerate mock decoders") Reviewed-by:
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Dan Williams authored
In support of testing DPA allocation mechanisms in the CXL core, the cxl_test environment needs to support establishing and retrieving the 'pmem partition boundary. Replace the platform_device_add_resources() method for delineating DPA within an endpoint with an emulated DEV_SIZE amount of partitionable capacity. Set DEV_SIZE such that an endpoint has enough capacity to simultaneously participate in 8 distinct regions. Reviewed-by:
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Dan Williams authored
For the x2 host-bridge interleave windows, allow for a x8-endpoint-interleave configuration per memory-type with each device contributing the minimum 256MB extent. Similarly, for the x1 host-bridge interleave windows, allow for a x4-endpoint-interleave configuration per memory-type. Bump up the number of decoders per-port to support hosting 8 regions. Reviewed-by:
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Dan Williams authored
A recent QEMU upgrade resulted in collisions between QEMU's chosen location for PCI MMIO and cxl_test's fake address location for emulated CXL purposes. This was great for testing resource collisions, but not so great for continuing to test the nominal cases. Move cxl_test to the top-of-memory where it is less likely to collide with other resources. Reviewed-by:
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Dan Williams authored
Dump the device-physical-address map for a CXL expander in /proc/iomem style format. E.g.: cat /sys/kernel/debug/cxl/mem1/dpamem 00000000-0fffffff : ram 10000000-1fffffff : pmem Reviewed-by:
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Dan Williams authored
In preparation for a new cxl debugfs file, move 'cxl' directory establishment and teardown to the core and let subsequent init routines reference that setup. Reviewed-by:
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