[RFC PATCH 0/2] Sbsa-ref CXL Enablement

[Yuquan Wang]

RFC because
- Many contents are ported from Jonathan' patch on qemu virt design

- Bring plenty of PCDs values and modifying the original PCIE values

- Less experience and not particularly confident in ACPI area so this might be
  stupidly broken in a way I've not considered.

Currently the base CXL support for arm platforms is only on Jonathan's 
patches[1] which
have not yet merged into upstream. SBSA-REF can be more like a real machine, 
thus the
support of cxl could be meaningful.

Regard to the burden of edk2 firmware, I try to build a static CEDT table and 
add acpi0016,
acpi0017 objects on DSDT at the initial development phase[2][3]. Hence it 
doesn't need to
communicate cxl contents via DT to edk2. 

This series leverages Jonathan's patches[1] to design [SBSA_CXL_HOST] and 
[SBSA_CXL_FIXED_WINDOW]
spaces for sbsa-ref layout. 

For [SBSA_CXL_HOST], new memory layout places 1M space for 16 host bridge 
register regions
in the sbsa-ref memmap. In addition, this only creates a default pxb-cxl 
(bus_nr=0xfe) bridge 
with one cxl-rp on sbsa-ref, so only one cxl device could be added by user on 
this cxl Bus.
With the 'create_pxb_cxl', users don't need to input '-device pxb-cxl' and 
'-device cxl-rp'
parameters.

For [SBSA_CXL_FIXED_WINDOW], this extends 1TB space from the hole above RAM 
Memory [SBSA_MEM]
for CXL Fixed Memory Window. 0xA0000000000 is chosen as the base address of 
this space because
of 3 reasons:

1) It is more suitable to choose a static address instead of that
implementation in virt, since a dynamic address space layout of
sbsa-ref is not appropriate for its original purpose as a reference
platform.

2) The Hotplug Memory address range should in the range of maximum
addressable range of sbsa-ref platform(0x10000000000-0x80ffffffffff).
It is satisfied the requirements of memory hotplug in linux kernel.

3) The start pfn of CFMW should exceed the reserved_pfn_range for
onlined numa node.

Based on 'cxl_fmws_link_targets', this adds a new function
'sbsa_cxl_fmws_link_targets' for binding cfmws.target with the default
pxb-cxl-bus on sbsa-ref.

In addition, this also adds 'create_cxl_fixed_window_region' which
based on 'machine_set_cfmw' to support creating a static cfmw region on
sbsa-ref, so users don't need to input '-M cxl-fmw' parameter.

Thus, to run sbsa-ref with a cxl device could use:
qemu-system-aarch64 \
-machine sbsa-ref \
-cpu cortex-a57 \
-smp 4 \
-m 4G \
-object memory-backend-ram,size=2G,id=mem0 \
-numa node,nodeid=0,cpus=0-1,memdev=mem0 \
-object memory-backend-ram,size=2G,id=mem1 \
-numa node,nodeid=1,cpus=2-3,memdev=mem1 \
-object memory-backend-file,id=mem2,mem-path=/tmp/mem2,size=256M,share=true \
-device cxl-type3,bus=cxl.0,volatile-memdev=mem2,id=cxl-mem1 \
-hda ubuntu.ext4 \
-pflash SBSA_FLASH0.fd \
-pflash SBSA_FLASH1.fd \

This series patches are here to hopefully some comments to guide me!

Link:
[1]: 
https://lore.kernel.org/linux-cxl/20220616141950.23374-1-Jonathan.Cameron@huawei.com/
[2]: https://edk2.groups.io/g/devel/topic/rfc_patch_0_1/108173029
[3]: https://edk2.groups.io/g/devel/topic/rfc_patch_edk2_platforms/108173682

Yuquan Wang (2):
  hw/arm/sbsa-ref: Enable CXL Host Bridge by pxb-cxl
  hw/arm/sbsa-ref: Support CXL Fixed Memory Window

 hw/arm/sbsa-ref.c                   | 127 +++++++++++++++++++++++++++-
 hw/cxl/cxl-host-stubs.c             |   1 +
 hw/cxl/cxl-host.c                   |   2 +-
 hw/pci-bridge/pci_expander_bridge.c |   1 -
 include/hw/cxl/cxl_host.h           |   1 +
 include/hw/pci/pci_bridge.h         |   1 +
 6 files changed, 128 insertions(+), 5 deletions(-)

-- 
2.34.1