A git tree of this series can be found here: https://github.com/weiny2/linux-kernel/tree/dcd-v4-2024-08-16 This series requires the CXL memory notifier lock change: https://lore.kernel.org/all/20240814-fix-notifiers-v2-1-6bab38192c7c@xxxxxxxxx/ Background ========== A Dynamic Capacity Device (DCD) (CXL 3.1 sec 9.13.3) is a CXL memory device that allows memory capacity within a region to change dynamically without the need for resetting the device, reconfiguring HDM decoders, or reconfiguring software DAX regions. One of the biggest use cases for Dynamic Capacity is to allow hosts to share memory dynamically within a data center without increasing the per-host attached memory. The general flow for the addition or removal of memory is to have an orchestrator coordinate the use of the memory. Generally there are 5 actors in such a system, the Orchestrator, Fabric Manager, the Logical device, the Host Kernel, and a Host User. Typical work flows are shown below. Orchestrator FM Device Host Kernel Host User | | | | | |-------------- Create region ----------------------->| | | | | | | | | |<-- Create ---| | | | | Region | |<------------- Signal done --------------------------| | | | | | |-- Add ----->|-- Add --->|--- Add --->| | | Capacity | Extent | Extent | | | | | | | | |<- Accept -|<- Accept -| | | | Extent | Extent | | | | | |<- Create --->| | | | | DAX dev |-- Use memory | | | | | | | | | | | | | | | |<- Release ---| <-+ | | | | DAX dev | | | | | | |<------------- Signal done --------------------------| | | | | | |-- Remove -->|- Release->|- Release ->| | | Capacity | Extent | Extent | | | | | | | | |<- Release-|<- Release -| | | | Extent | Extent | | | | | | | |-- Add ----->|-- Add --->|--- Add --->| | | Capacity | Extent | Extent | | | | | | | | |<- Accept -|<- Accept -| | | | Extent | Extent | | | | | |<- Create ----| | | | | DAX dev |-- Use memory | | | | | | | | | |<- Release ---| <-+ | | | | DAX dev | |<------------- Signal done --------------------------| | | | | | |-- Remove -->|- Release->|- Release ->| | | Capacity | Extent | Extent | | | | | | | | |<- Release-|<- Release -| | | | Extent | Extent | | | | | | | |-- Add ----->|-- Add --->|--- Add --->| | | Capacity | Extent | Extent | | | | | |<- Create ----| | | | | DAX dev |-- Use memory | | | | | | |-- Remove -->|- Release->|- Release ->| | | | Capacity | Extent | Extent | | | | | | | | | | | | (Release Ignored) | | | | | | | | | | | |<- Release ---| <-+ | | | | DAX dev | |<------------- Signal done --------------------------| | | | | | | |- Release->|- Release ->| | | | Extent | Extent | | | | | | | | |<- Release-|<- Release -| | | | Extent | Extent | | | | | |<- Destroy ---| | | | | Region | | | | | | Previous versions of this series[0] resulted in architectural comments as well as confusion on the architecture based on the organization of patch series itself. This version has reordered the patches to clarify the architecture. It also streamlines extent handling more. The series still requires the creation of regions and DAX devices to be synchronized with the Orchestrator and Fabric Manager. The host kernel will reject an add extent event if the region is not created yet. It will also ignore a release if the DAX device is created and referencing an extent. These synchronizations are not anticipated to be an issue with real applications. In order to allow for capacity to be added and removed a new concept of a sparse DAX region is introduced. A sparse DAX region may have 0 or more bytes of available space. The total space depends on the number and size of the extents which have been added. Initially it is anticipated that users of the memory will carefully coordinate the surfacing of additional capacity with the creation of DAX devices which use that capacity. Therefore, the allocation of the memory to DAX devices does not allow for specific associations between DAX device and extent. This keeps allocations very similar to existing DAX region behavior. Great care was taken to keep the extent tracking simple. Some xarray's needed to be added but extra software objects were kept to a minimum. Region extents continue to be tracked as sub-devices of the DAX region. This ensures that region destruction cleans up all extent allocations properly. Due to these major changes all reviews were removed from the larger patches. A few of the straight forward patches have kept the tags. In summary the major functionality of this series includes: - Getting the dynamic capacity (DC) configuration information from cxl devices - Configuring the DC partitions reported by hardware - Enhancing the CXL and DAX regions for dynamic capacity support a. Maintain a logical separation between hardware extents and software managed region extents. This provides an abstraction between the layers and should allow for interleaving in the future - Get hardware extent lists for endpoint decoders upon region creation. - Adjust extent/region memory available on the following events. a. Add capacity Events b. Release capacity events - Host response for add capacity a. do not accept the extent if: If the region does not exist or an error occurs realizing the extent b. If the region does exist realize a DAX region extent with 1:1 mapping (no interleave yet) c. Support the more bit by processing a list of extents marked with the more bit together before setting up a response. - Host response for remove capacity a. If no DAX device references the extent; release the extent b. If a reference does exist, ignore the request. (Require FM to issue release again.) - Modify DAX device creation/resize to account for extents within a sparse DAX region - Trace Dynamic Capacity events for debugging - Add cxl-test infrastructure to allow for faster unit testing (See new ndctl branch for cxl-dcd.sh test[1]) Fan Ni's upstream of Qemu DCD was used for testing. Remaining work: 1) Integrate the QoS work from Dave Jiang 2) Interleave support Possible additional work depending on requirements: 1) Allow mapping to specific extents (perhaps based on label/tag) 2) Release extents when DAX devices are released if a release was previously seen from the device 3) Accept a new extent which extends (but overlaps) an existing extent(s) 4) Rework DAX device interfaces, memfd has been explored a bit [0] v1: https://lore.kernel.org/all/20240324-dcd-type2-upstream-v1-0-b7b00d623625@xxxxxxxxx/ [1] https://github.com/weiny2/ndctl/tree/dcd-region2-2024-08-15 --- Major changes: - Jonathan: support the more bit - djbw: Allow more than 1 region per DC partition - All: Address the many comments on the series. - iweiny: rebase - iweiny: Rework the series to make it easier to review and understand the flow - Link to v1: https://lore.kernel.org/r/20240324-dcd-type2-upstream-v1-0-b7b00d623625@xxxxxxxxx - Link to v2: https://lore.kernel.org/all/20240816-dcd-type2-upstream-v2-0-20189a10ad7d@xxxxxxxxx/ --- Ira Weiny (11): range: Add range_overlaps() printk: Add print format (%par) for struct range dax: Document dax dev range tuple cxl/pci: Delay event buffer allocation cxl/region: Refactor common create region code cxl/events: Split event msgnum configuration from irq setup cxl/pci: Factor out interrupt policy check cxl/core: Return endpoint decoder information from region search dax/bus: Factor out dev dax resize logic tools/testing/cxl: Make event logs dynamic tools/testing/cxl: Add DC Regions to mock mem data Navneet Singh (14): cxl/mbox: Flag support for Dynamic Capacity Devices (DCD) cxl/mem: Read dynamic capacity configuration from the device cxl/core: Separate region mode from decoder mode cxl/region: Add dynamic capacity decoder and region modes cxl/hdm: Add dynamic capacity size support to endpoint decoders cxl/port: Add endpoint decoder DC mode support to sysfs cxl/mem: Expose DCD partition capabilities in sysfs cxl/region: Add sparse DAX region support cxl/mem: Configure dynamic capacity interrupts cxl/extent: Process DCD events and realize region extents cxl/region/extent: Expose region extent information in sysfs dax/region: Create resources on sparse DAX regions cxl/region: Read existing extents on region creation cxl/mem: Trace Dynamic capacity Event Record Documentation/ABI/testing/sysfs-bus-cxl | 68 ++- Documentation/core-api/printk-formats.rst | 14 + drivers/cxl/core/Makefile | 2 +- drivers/cxl/core/core.h | 33 +- drivers/cxl/core/extent.c | 467 ++++++++++++++ drivers/cxl/core/hdm.c | 206 ++++++- drivers/cxl/core/mbox.c | 578 +++++++++++++++++- drivers/cxl/core/memdev.c | 101 ++- drivers/cxl/core/port.c | 13 +- drivers/cxl/core/region.c | 173 ++++-- drivers/cxl/core/trace.h | 65 ++ drivers/cxl/cxl.h | 122 +++- drivers/cxl/cxlmem.h | 128 +++- drivers/cxl/pci.c | 123 +++- drivers/dax/bus.c | 352 +++++++++-- drivers/dax/bus.h | 4 +- drivers/dax/cxl.c | 73 ++- drivers/dax/dax-private.h | 39 +- drivers/dax/hmem/hmem.c | 2 +- drivers/dax/pmem.c | 2 +- fs/btrfs/ordered-data.c | 10 +- include/linux/cxl-event.h | 32 + include/linux/range.h | 7 + lib/vsprintf.c | 37 ++ tools/testing/cxl/Kbuild | 3 +- tools/testing/cxl/test/mem.c | 981 ++++++++++++++++++++++++++---- 26 files changed, 3327 insertions(+), 308 deletions(-) --- base-commit: 3cef9316df4cda21b5bf25e4230221b02050dfa1 change-id: 20230604-dcd-type2-upstream-0cd15f6216fd Best regards, -- Ira Weiny <ira.weiny@xxxxxxxxx>
