[PATCH RFC -qemu 0/2] hw/cxl: Support Back Invalidation

[Davidlohr Bueso <dave@stgolabs.net>]

Hello,

The following allows support for component basic back invalidation discovery
and config, by exposing the BI routing table and decoder registers. Instead
of going the type2[1] route, this series proposes adding support for type3
hdm-db, which allows a more direct way of supporting BI in qemu.

Caveats/RFC: Just as in Ira's series, there is the question about the whole topology
allowing BI, not just the endpoint device. That series left the rest of topology
(dsp, rp) non-BI capable, for which any kernel counterpart testing would fail
when using type2, but at the same time is also consistent with flit 68B when not
using a type2 device.

This series blindly enables BI capabilities for ports even when no type3 hdm-db
is being used. While it is handy, it is inconsistent with the driver seeing 68B
and the BI registers in such cases. I've been going back and forth with possible
workarounds, but don't really have a good answer, and this will ultimately
affect not only BI but all goodies that come with 256B flit. Any suggestions welcome.

Patch 1: is lifted from Ira's series with some small (but non-trivial) changes.
Patch 2: adds BI decoder/rt register support.

Testing wise, this has passed relevant kernel side BI register IO flows and
setup.

Applies against branch 'origin/cxl-2025-07-03' from the jic23 repository.

Thanks!

[1] https://lore.kernel.org/linux-cxl/20230517-rfc-type2-dev-v1-0-6eb2e470981b@intel.com/

Davidlohr Bueso (1):
  hw/cxl: Support Type3 HDM-DB

Ira Weiny (1):
  hw/cxl: Refactor component register initialization

 hw/cxl/cxl-component-utils.c   | 206 ++++++++++++++++++++++++---------
 hw/mem/cxl_type3.c             |   5 +-
 include/hw/cxl/cxl_component.h |  87 +++++++++++---
 include/hw/cxl/cxl_device.h    |   3 +
 4 files changed, 232 insertions(+), 69 deletions(-)

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2.39.5