Re: [PATCH 00/23] cxl_test: Enable CXL Topology and UAPI regression tests

[Ben Widawsky <ben.widawsky@intel.com>]

On 21-08-09 15:27:47, Dan Williams wrote:
> As mentioned in patch 20 in this series the response of upstream QEMU
> community to CXL device emulation has been underwhelming to date. Even
> if that picked up it still results in a situation where new driver
> features and new test capabilities for those features are split across
> multiple repositories.
> 
> The "nfit_test" approach of mocking up platform resources via an
> external test module continues to yield positive results catching
> regressions early and often. Repeat that success with a "cxl_test"
> module to inject custom crafted topologies and command responses into
> the CXL subsystem's sysfs and ioctl UAPIs.
> 
> The first target for cxl_test to verify is the integration of CXL with
> LIBNVDIMM and the new support for the CXL namespace label + region-label
> format. The first 11 patches introduce support for the new label format.
> 
> The next 9 patches rework the CXL PCI driver and to move more common
> infrastructure into the core for the unit test environment to reuse. The
> largest change here is disconnecting the mailbox command processing
> infrastructure from the PCI specific transport. The unit test
> environment replaces the PCI transport with a custom backend with mocked
> responses to command requests.
> 
> Patch 20 introduces just enough mocked functionality for the cxl_acpi
> driver to load against cxl_test resources. Patch 21 fixes the first bug
> discovered by this framework, namely that HDM decoder target list maps
> were not being filled out.
> 
> Finally patches 22 and 23 introduce a cxl_test representation of memory
> expander devices. In this initial implementation these memory expander
> targets implement just enough command support to pass the basic driver
> init sequence and enable label command passthrough to LIBNVDIMM.
> 
> The topology of cxl_test includes:
> - (4) platform fixed memory windows. One each of a x1-volatile,
>   x4-volatile, x1-persistent, and x4-persistent.
> - (4) Host bridges each with (2) root ports
> - (8) CXL memory expanders, one for each root port
> - Each memory expander device supports the GET_SUPPORTED_LOGS, GET_LOG,
>   IDENTIFY, GET_LSA, and SET_LSA commands.
> 
> Going forward the expectation is that where possible new UAPI visible
> subsystem functionality comes with cxl_test emulation of the same.
> 
> The build process for cxl_test is:
> 
>     make M=tools/testing/cxl
>     make M=tools/testing/cxl modules_install
> 
> The implementation methodology of the test module is the same as
> nfit_test where the bulk of the emulation comes from replacing symbols
> that cxl_acpi and the cxl_core import with mocked implementation of
> those symbols. See the "--wrap=" lines in tools/testing/cxl/Kbuild. Some
> symbols need to be replaced, but are local to the modules like
> match_add_root_ports(). In those cases the local symbol is marked __weak
> with a strong implementation coming from tools/testing/cxl/. The goal
> being to be minimally invasive to production code paths.

I went through everything except the very last patch, which I'll try to get to
tomorrow when my brain is working a bit better. It looks fine to me overall. I'd
like if we could remove code duplication in the mock driver, but perhaps that's
the nature of the beast here.

> 
> ---
> 
> Dan Williams (23):
>       libnvdimm/labels: Introduce getters for namespace label fields
>       libnvdimm/labels: Add isetcookie validation helper
>       libnvdimm/labels: Introduce label setter helpers
>       libnvdimm/labels: Add a checksum calculation helper
>       libnvdimm/labels: Add blk isetcookie set / validation helpers
>       libnvdimm/labels: Add blk special cases for nlabel and position helpers
>       libnvdimm/labels: Add type-guid helpers
>       libnvdimm/labels: Add claim class helpers
>       libnvdimm/labels: Add address-abstraction uuid definitions
>       libnvdimm/labels: Add uuid helpers
>       libnvdimm/labels: Introduce CXL labels
>       cxl/pci: Make 'struct cxl_mem' device type generic
>       cxl/mbox: Introduce the mbox_send operation
>       cxl/mbox: Move mailbox and other non-PCI specific infrastructure to the core
>       cxl/pci: Use module_pci_driver
>       cxl/mbox: Convert 'enabled_cmds' to DECLARE_BITMAP
>       cxl/mbox: Add exclusive kernel command support
>       cxl/pmem: Translate NVDIMM label commands to CXL label commands
>       cxl/pmem: Add support for multiple nvdimm-bridge objects
>       tools/testing/cxl: Introduce a mocked-up CXL port hierarchy
>       cxl/bus: Populate the target list at decoder create
>       cxl/mbox: Move command definitions to common location
>       tools/testing/cxl: Introduce a mock memory device + driver
> 
> 
>  Documentation/driver-api/cxl/memory-devices.rst |    3 
>  drivers/cxl/acpi.c                              |   65 +
>  drivers/cxl/core/Makefile                       |    1 
>  drivers/cxl/core/bus.c                          |   69 +-
>  drivers/cxl/core/core.h                         |    8 
>  drivers/cxl/core/mbox.c                         |  796 +++++++++++++++++
>  drivers/cxl/core/memdev.c                       |   84 ++
>  drivers/cxl/core/pmem.c                         |   32 +
>  drivers/cxl/cxl.h                               |   35 -
>  drivers/cxl/cxlmem.h                            |  186 ++++
>  drivers/cxl/pci.c                               | 1053 +----------------------
>  drivers/cxl/pmem.c                              |  162 +++-
>  drivers/nvdimm/btt.c                            |   11 
>  drivers/nvdimm/btt.h                            |    4 
>  drivers/nvdimm/btt_devs.c                       |   12 
>  drivers/nvdimm/core.c                           |   40 -
>  drivers/nvdimm/label.c                          |  354 +++++---
>  drivers/nvdimm/label.h                          |   96 +-
>  drivers/nvdimm/namespace_devs.c                 |  194 ++--
>  drivers/nvdimm/nd-core.h                        |    5 
>  drivers/nvdimm/nd.h                             |  263 ++++++
>  drivers/nvdimm/pfn_devs.c                       |    2 
>  include/linux/nd.h                              |    4 
>  tools/testing/cxl/Kbuild                        |   29 +
>  tools/testing/cxl/mock_acpi.c                   |  105 ++
>  tools/testing/cxl/mock_pmem.c                   |   24 +
>  tools/testing/cxl/test/Kbuild                   |   10 
>  tools/testing/cxl/test/cxl.c                    |  587 +++++++++++++
>  tools/testing/cxl/test/mem.c                    |  255 ++++++
>  tools/testing/cxl/test/mock.c                   |  155 +++
>  tools/testing/cxl/test/mock.h                   |   27 +
>  31 files changed, 3234 insertions(+), 1437 deletions(-)
>  create mode 100644 drivers/cxl/core/mbox.c
>  create mode 100644 tools/testing/cxl/Kbuild
>  create mode 100644 tools/testing/cxl/mock_acpi.c
>  create mode 100644 tools/testing/cxl/mock_pmem.c
>  create mode 100644 tools/testing/cxl/test/Kbuild
>  create mode 100644 tools/testing/cxl/test/cxl.c
>  create mode 100644 tools/testing/cxl/test/mem.c
>  create mode 100644 tools/testing/cxl/test/mock.c
>  create mode 100644 tools/testing/cxl/test/mock.h
> 
> base-commit: 427832674f6e2413c21ca2271ec945a720608ff2
> 
> (cxl.git#pending as of August 9th, 2021)