[PATCH 0/1] cxl/cxl-host: Support creation of a new CXL Host Bridge

[Yuquan Wang]

Background
==========
Currently the base CXL support for arm platforms is only on Jonathan's
patches[1] which have not yet merged into upstream. Some platform like
SBSA-REF can be more like a real machine, thus the support of cxl could
be meaningful. However, the pxb-cxl-host realization on this platform
seems not satisfying their requirements[2].

New CXL HOST design
===================
This work defines a new cxl host bridge type (TYPE_CXL_HOST). This
could be considered as a prototype of an independent cxl host bridge
which combines gpex features (ecam, mmio windows & irq) and pxb-cxl
features(CHBCR) at meanwhile.

The root bus path of CXL_HOST is "0001:00", that would not affect the
original pcie host topology. In the previous, the pxb-cxl-host with
any cxl root ports and cxl endpoint devices would occupy the BDF
number of the original pcie domain. This new type provide a solution
to resolve the problem.

Also the CXLFixedWindow struct adds a new member 'target_chb' to
record the target list of CXLHostBridge. And necessary is to adjust
the logic of 'cxl_cfmws_find_device' and 'cxl_fmws_link_targets' to
allow different types of cxl host bridge.

Move 'cxl_get_hb_cstate' & 'cxl_get_hb_passthrough' from pxb code
into cxl-host code.

Link:
[1]: 
https://lore.kernel.org/linux-cxl/20220616141950.23374-1-Jonathan.Cameron@huawei.com/
[2]: https://lists.nongnu.org/archive/html/qemu-arm/2024-11/msg00522.html

Yuquan Wang (1):
  cxl/cxl-host: Support creation of a new CXL Host Bridge

 hw/cxl/cxl-host-stubs.c             |   2 +
 hw/cxl/cxl-host.c                   | 220 ++++++++++++++++++++++++++--
 hw/pci-bridge/pci_expander_bridge.c |  20 +--
 include/hw/cxl/cxl.h                |  23 +++
 include/hw/cxl/cxl_component.h      |   4 +-
 include/hw/cxl/cxl_host.h           |   6 +
 6 files changed, 242 insertions(+), 33 deletions(-)

-- 
2.34.1