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author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-25 04:07:03 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-25 04:07:03 +0300 |
commit | b9132c32e01976686efa26252cc246944a0d2cab (patch) | |
tree | fe93979a569002f6f9a4188b1f21d475bbdec82b /Documentation | |
parent | b14ffae378aa1db993e62b01392e70d1e585fb23 (diff) | |
parent | 05e815539f3f161585c13a9ab023341bade2c52f (diff) | |
download | linux-b9132c32e01976686efa26252cc246944a0d2cab.tar.xz |
Merge tag 'cxl-for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl
Pull CXL (Compute Express Link) updates from Dan Williams:
"This development cycle extends the subsystem to discover CXL resources
throughout a CXL/PCIe switch topology and respond to hot add/remove
events anywhere in that topology.
This is more foundational infrastructure in preparation for dynamic
memory region provisioning support. Recall that CXL memory regions, as
the new "Theory of Operation" section of
Documentation/driver-api/cxl/memory-devices.rst describes, bring
storage volume striping semantics to memory.
The hot add/remove behavior is validated with extensions to the
cxl_test unit test environment and this test in the cxl-cli test
suite:
https://github.com/pmem/ndctl/blob/djbw/for-74/cxl/test/cxl-topology.sh
Summary:
- Add a driver for 'struct cxl_memdev' objects responsible for
CXL.mem operation as distinct from 'cxl_pci' mailbox operations.
Its primary responsibility is enumerating an endpoint 'struct
cxl_port' and all the 'struct cxl_port' instances between an
endpoint and the CXL platform root.
- Add a driver for 'struct cxl_port' objects responsible for
enumerating and operating all Host-managed Device Memory (HDM)
decoder resources between the platform-level CXL memory
description, all intervening host bridges / switches, and the HDM
resources in endpoints.
- Update the cxl_pci driver to validate CXL.mem operation precursors
to HDM decoder operation like ready-polling, and legacy CXL 1.1
DVSEC based CXL.mem configuration.
- Add basic lockdep coverage for usage of device_lock() on CXL
subsystem objects similar to what exists for LIBNVDIMM. Include a
compile-time switch for which subsystem to validate at run-time.
- Update cxl_test to emulate a one level switch topology.
- Document a "Theory of Operation" for the subsystem.
- Add 'numa_node' and 'serial' attributes to cxl_memdev sysfs
- Include miscellaneous fixes for spec / QEMU CXL emulation
compatibility and static analysis reports"
* tag 'cxl-for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl: (48 commits)
cxl/core/port: Fix NULL but dereferenced coccicheck error
cxl/port: Hold port reference until decoder release
cxl/port: Fix endpoint refcount leak
cxl/core: Fix cxl_device_lock() class detection
cxl/core/port: Fix unregister_port() lock assertion
cxl/regs: Fix size of CXL Capability Header Register
cxl/core/port: Handle invalid decoders
cxl/core/port: Fix / relax decoder target enumeration
tools/testing/cxl: Add a physical_node link
tools/testing/cxl: Enumerate mock decoders
tools/testing/cxl: Mock one level of switches
tools/testing/cxl: Fix root port to host bridge assignment
tools/testing/cxl: Mock dvsec_ranges()
cxl/core/port: Add endpoint decoders
cxl/core: Move target_list out of base decoder attributes
cxl/mem: Add the cxl_mem driver
cxl/core/port: Add switch port enumeration
cxl/memdev: Add numa_node attribute
cxl/pci: Emit device serial number
cxl/pci: Implement wait for media active
...
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/ABI/testing/sysfs-bus-cxl | 36 | ||||
-rw-r--r-- | Documentation/driver-api/cxl/memory-devices.rst | 315 |
2 files changed, 349 insertions, 2 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl index 0b6a2e6e8fbb..7c2b846521f3 100644 --- a/Documentation/ABI/testing/sysfs-bus-cxl +++ b/Documentation/ABI/testing/sysfs-bus-cxl @@ -1,3 +1,12 @@ +What: /sys/bus/cxl/flush +Date: Januarry, 2022 +KernelVersion: v5.18 +Contact: linux-cxl@vger.kernel.org +Description: + (WO) If userspace manually unbinds a port the kernel schedules + all descendant memdevs for unbind. Writing '1' to this attribute + flushes that work. + What: /sys/bus/cxl/devices/memX/firmware_version Date: December, 2020 KernelVersion: v5.12 @@ -25,6 +34,24 @@ Description: identically named field in the Identify Memory Device Output Payload in the CXL-2.0 specification. +What: /sys/bus/cxl/devices/memX/serial +Date: January, 2022 +KernelVersion: v5.18 +Contact: linux-cxl@vger.kernel.org +Description: + (RO) 64-bit serial number per the PCIe Device Serial Number + capability. Mandatory for CXL devices, see CXL 2.0 8.1.12.2 + Memory Device PCIe Capabilities and Extended Capabilities. + +What: /sys/bus/cxl/devices/memX/numa_node +Date: January, 2022 +KernelVersion: v5.18 +Contact: linux-cxl@vger.kernel.org +Description: + (RO) If NUMA is enabled and the platform has affinitized the + host PCI device for this memory device, emit the CPU node + affinity for this device. + What: /sys/bus/cxl/devices/*/devtype Date: June, 2021 KernelVersion: v5.14 @@ -34,6 +61,15 @@ Description: the same value communicated in the DEVTYPE environment variable for uevents for devices on the "cxl" bus. +What: /sys/bus/cxl/devices/*/modalias +Date: December, 2021 +KernelVersion: v5.18 +Contact: linux-cxl@vger.kernel.org +Description: + CXL device objects export the modalias attribute which mirrors + the same value communicated in the MODALIAS environment variable + for uevents for devices on the "cxl" bus. + What: /sys/bus/cxl/devices/portX/uport Date: June, 2021 KernelVersion: v5.14 diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst index 3b8f41395f6b..db476bb170b6 100644 --- a/Documentation/driver-api/cxl/memory-devices.rst +++ b/Documentation/driver-api/cxl/memory-devices.rst @@ -14,6 +14,303 @@ that optionally define a device's contribution to an interleaved address range across multiple devices underneath a host-bridge or interleaved across host-bridges. +CXL Bus: Theory of Operation +============================ +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. + +Platform firmware enumerates a menu of interleave options at the "CXL root port" +(Linux term for the top of the CXL decode topology). From there, PCIe topology +dictates which endpoints can participate in which Host Bridge decode regimes. +Each PCIe Switch in the path between the root and an endpoint introduces a point +at which the interleave can be split. For example platform firmware may say at a +given range only decodes to 1 one Host Bridge, but that Host Bridge may in turn +interleave cycles across multiple Root Ports. An intervening Switch between a +port and an endpoint may interleave cycles across multiple Downstream Switch +Ports, etc. + +Here is a sample listing of a CXL topology defined by 'cxl_test'. The 'cxl_test' +module generates an emulated CXL topology of 2 Host Bridges each with 2 Root +Ports. Each of those Root Ports are connected to 2-way switches with endpoints +connected to those downstream ports for a total of 8 endpoints:: + + # cxl list -BEMPu -b cxl_test + { + "bus":"root3", + "provider":"cxl_test", + "ports:root3":[ + { + "port":"port5", + "host":"cxl_host_bridge.1", + "ports:port5":[ + { + "port":"port8", + "host":"cxl_switch_uport.1", + "endpoints:port8":[ + { + "endpoint":"endpoint9", + "host":"mem2", + "memdev":{ + "memdev":"mem2", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x1", + "numa_node":1, + "host":"cxl_mem.1" + } + }, + { + "endpoint":"endpoint15", + "host":"mem6", + "memdev":{ + "memdev":"mem6", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x5", + "numa_node":1, + "host":"cxl_mem.5" + } + } + ] + }, + { + "port":"port12", + "host":"cxl_switch_uport.3", + "endpoints:port12":[ + { + "endpoint":"endpoint17", + "host":"mem8", + "memdev":{ + "memdev":"mem8", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x7", + "numa_node":1, + "host":"cxl_mem.7" + } + }, + { + "endpoint":"endpoint13", + "host":"mem4", + "memdev":{ + "memdev":"mem4", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x3", + "numa_node":1, + "host":"cxl_mem.3" + } + } + ] + } + ] + }, + { + "port":"port4", + "host":"cxl_host_bridge.0", + "ports:port4":[ + { + "port":"port6", + "host":"cxl_switch_uport.0", + "endpoints:port6":[ + { + "endpoint":"endpoint7", + "host":"mem1", + "memdev":{ + "memdev":"mem1", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0", + "numa_node":0, + "host":"cxl_mem.0" + } + }, + { + "endpoint":"endpoint14", + "host":"mem5", + "memdev":{ + "memdev":"mem5", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x4", + "numa_node":0, + "host":"cxl_mem.4" + } + } + ] + }, + { + "port":"port10", + "host":"cxl_switch_uport.2", + "endpoints:port10":[ + { + "endpoint":"endpoint16", + "host":"mem7", + "memdev":{ + "memdev":"mem7", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x6", + "numa_node":0, + "host":"cxl_mem.6" + } + }, + { + "endpoint":"endpoint11", + "host":"mem3", + "memdev":{ + "memdev":"mem3", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x2", + "numa_node":0, + "host":"cxl_mem.2" + } + } + ] + } + ] + } + ] + } + +In that listing each "root", "port", and "endpoint" object correspond a kernel +'struct cxl_port' object. A 'cxl_port' is a device that can decode CXL.mem to +its descendants. So "root" claims non-PCIe enumerable platform decode ranges and +decodes them to "ports", "ports" decode to "endpoints", and "endpoints" +represent the decode from SPA (System Physical Address) to DPA (Device Physical +Address). + +Continuing the RAID analogy, disks have both topology metadata and on device +metadata that determine RAID set assembly. CXL Port topology and CXL Port link +status is metadata for CXL.mem set assembly. The CXL Port topology is enumerated +by the arrival of a CXL.mem device. I.e. unless and until the PCIe core attaches +the cxl_pci driver to a CXL Memory Expander there is no role for CXL Port +objects. Conversely for hot-unplug / removal scenarios, there is no need for +the Linux PCI core to tear down switch-level CXL resources because the endpoint +->remove() event cleans up the port data that was established to support that +Memory Expander. + +The port metadata and potential decode schemes that a give memory device may +participate can be determined via a command like:: + + # cxl list -BDMu -d root -m mem3 + { + "bus":"root3", + "provider":"cxl_test", + "decoders:root3":[ + { + "decoder":"decoder3.1", + "resource":"0x8030000000", + "size":"512.00 MiB (536.87 MB)", + "volatile_capable":true, + "nr_targets":2 + }, + { + "decoder":"decoder3.3", + "resource":"0x8060000000", + "size":"512.00 MiB (536.87 MB)", + "pmem_capable":true, + "nr_targets":2 + }, + { + "decoder":"decoder3.0", + "resource":"0x8020000000", + "size":"256.00 MiB (268.44 MB)", + "volatile_capable":true, + "nr_targets":1 + }, + { + "decoder":"decoder3.2", + "resource":"0x8050000000", + "size":"256.00 MiB (268.44 MB)", + "pmem_capable":true, + "nr_targets":1 + } + ], + "memdevs:root3":[ + { + "memdev":"mem3", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x2", + "numa_node":0, + "host":"cxl_mem.2" + } + ] + } + +...which queries the CXL topology to ask "given CXL Memory Expander with a kernel +device name of 'mem3' which platform level decode ranges may this device +participate". A given expander can participate in multiple CXL.mem interleave +sets simultaneously depending on how many decoder resource it has. In this +example mem3 can participate in one or more of a PMEM interleave that spans to +Host Bridges, a PMEM interleave that targets a single Host Bridge, a Volatile +memory interleave that spans 2 Host Bridges, and a Volatile memory interleave +that only targets a single Host Bridge. + +Conversely the memory devices that can participate in a given platform level +decode scheme can be determined via a command like the following:: + + # cxl list -MDu -d 3.2 + [ + { + "memdevs":[ + { + "memdev":"mem1", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0", + "numa_node":0, + "host":"cxl_mem.0" + }, + { + "memdev":"mem5", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x4", + "numa_node":0, + "host":"cxl_mem.4" + }, + { + "memdev":"mem7", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x6", + "numa_node":0, + "host":"cxl_mem.6" + }, + { + "memdev":"mem3", + "pmem_size":"256.00 MiB (268.44 MB)", + "ram_size":"256.00 MiB (268.44 MB)", + "serial":"0x2", + "numa_node":0, + "host":"cxl_mem.2" + } + ] + }, + { + "root decoders":[ + { + "decoder":"decoder3.2", + "resource":"0x8050000000", + "size":"256.00 MiB (268.44 MB)", + "pmem_capable":true, + "nr_targets":1 + } + ] + } + ] + +...where the naming scheme for decoders is "decoder<port_id>.<instance_id>". + Driver Infrastructure ===================== @@ -28,6 +325,14 @@ CXL Memory Device .. kernel-doc:: drivers/cxl/pci.c :internal: +.. kernel-doc:: drivers/cxl/mem.c + :doc: cxl mem + +CXL Port +-------- +.. kernel-doc:: drivers/cxl/port.c + :doc: cxl port + CXL Core -------- .. kernel-doc:: drivers/cxl/cxl.h @@ -36,10 +341,16 @@ CXL Core .. kernel-doc:: drivers/cxl/cxl.h :internal: -.. kernel-doc:: drivers/cxl/core/bus.c +.. kernel-doc:: drivers/cxl/core/port.c :doc: cxl core -.. kernel-doc:: drivers/cxl/core/bus.c +.. kernel-doc:: drivers/cxl/core/port.c + :identifiers: + +.. kernel-doc:: drivers/cxl/core/pci.c + :doc: cxl core pci + +.. kernel-doc:: drivers/cxl/core/pci.c :identifiers: .. kernel-doc:: drivers/cxl/core/pmem.c |