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Message-ID: <d02f217d-ae4f-476c-a20b-2b449cff73c0@intel.com> Date: Fri, 8 Nov 2024 10:27:28 -0700 From: Dave Jiang <dave.jiang@...el.com> To: Ira Weiny <ira.weiny@...el.com>, Fan Ni <fan.ni@...sung.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, Navneet Singh <navneet.singh@...el.com>, Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org> Cc: Dan Williams <dan.j.williams@...el.com>, Davidlohr Bueso <dave@...olabs.net>, Alison Schofield <alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>, linux-cxl@...r.kernel.org, linux-doc@...r.kernel.org, nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org, Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org, Johannes Thumshirn <johannes.thumshirn@....com>, Robert Moore <robert.moore@...el.com>, Len Brown <lenb@...nel.org>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, linux-acpi@...r.kernel.org, acpica-devel@...ts.linux.dev, Li Ming <ming4.li@...el.com>, Kees Cook <kees@...nel.org>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, linux-hardening@...r.kernel.org Subject: Re: [PATCH v7 00/27] DCD: Add support for Dynamic Capacity Devices (DCD) On 11/7/24 1:58 PM, Ira Weiny wrote: > A git tree of this series can be found here: > > https://github.com/weiny2/linux-kernel/tree/dcd-v4-2024-11-07 > > This is a quick spin with minor clean ups Dave was going to apply as > well as a couple of clean ups I had slated for after V4 landed. Top 6 patches (for DCD preparation) applied to cxl/next for 6.13 merge window. > > Series info > =========== > > This series has 4 parts: > > Patch 1: Add core range_overlaps() function > Patch 2-6: CXL clean up/prelim patches > Patch 7-25: Core DCD support > Patch 26-27: cxl_test support > > Patches 1-6 have received a lot of review and can be applied to cxl-next > straight away. While 7-27 may need to wait for Dan review. > > 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 | > | | | | | > > Implementation > ============== > > The series still requires the creation of regions and DAX devices to be > closely synchronized with the Orchestrator and Fabric Manager. The host > kernel will reject extents if a region is not yet created. It also > ignores extent release if memory is in use (DAX device created). 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. > > To keep the DAX memory allocation aligned with the existing DAX devices > which do not have tags extents are not allowed to have tags. Future > support for tags is planned. > > 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. > > Some review tags were kept if a patch did not change. > > 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 event 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]) > > - Only support 0 value extent tags > > Fan Ni's upstream of Qemu DCD was used for testing. > > Remaining work: > > 1) Allow mapping to specific extents (perhaps based on > label/tag) > 1a) devise region size reporting based on tags > 2) Interleave support > > Possible additional work depending on requirements: > > 1) Accept a new extent which extends (but overlaps) an existing > extent(s) > 2) Release extents when DAX devices are released if a release > was previously seen from the device > 3) Rework DAX device interfaces, memfd has been explored a bit > > [1] https://github.com/weiny2/ndctl/tree/dcd-region2-2024-10-01 > > --- > Changes in v7: > - Pick up review tags > - Ming: Fix setting the more flag > - Link to v6: https://patch.msgid.link/20241105-dcd-type2-upstream-v6-0-85c7fa2140fe@intel.com > > --- > Ira Weiny (13): > range: Add range_overlaps() > ACPI/CDAT: Add CDAT/DSMAS shared and read only flag values > dax: Document struct dev_dax_range > cxl/pci: Delay event buffer allocation > cxl/hdm: Use guard() in cxl_dpa_set_mode() > cxl/region: Refactor common create region code > cxl/cdat: Gather DSMAS data for DCD regions > 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/mem: Expose DCD partition capabilities in sysfs > cxl/port: Add endpoint decoder DC mode support to 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 | 125 +++- > drivers/cxl/core/Makefile | 2 +- > drivers/cxl/core/cdat.c | 45 +- > drivers/cxl/core/core.h | 34 +- > drivers/cxl/core/extent.c | 502 +++++++++++++++ > drivers/cxl/core/hdm.c | 231 ++++++- > drivers/cxl/core/mbox.c | 610 +++++++++++++++++- > drivers/cxl/core/memdev.c | 128 +++- > drivers/cxl/core/port.c | 19 +- > drivers/cxl/core/region.c | 185 ++++-- > drivers/cxl/core/trace.h | 65 ++ > drivers/cxl/cxl.h | 122 +++- > drivers/cxl/cxlmem.h | 132 +++- > drivers/cxl/pci.c | 122 +++- > drivers/dax/bus.c | 356 +++++++++-- > drivers/dax/bus.h | 4 +- > drivers/dax/cxl.c | 71 ++- > drivers/dax/dax-private.h | 66 +- > drivers/dax/hmem/hmem.c | 2 +- > drivers/dax/pmem.c | 2 +- > fs/btrfs/ordered-data.c | 10 +- > include/acpi/actbl1.h | 2 + > include/cxl/event.h | 32 + > include/linux/ioport.h | 3 + > include/linux/range.h | 8 + > tools/testing/cxl/Kbuild | 3 +- > tools/testing/cxl/test/mem.c | 1019 +++++++++++++++++++++++++++---- > 27 files changed, 3568 insertions(+), 332 deletions(-) > --- > base-commit: c2ee9f594da826bea183ed14f2cc029c719bf4da > change-id: 20230604-dcd-type2-upstream-0cd15f6216fd > > Best regards,
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