qemu/hw/pci-bridge
Ben Widawsky 3d6a69b6eb acpi/cxl: Create the CEDT (9.14.1)
The CXL Early Discovery Table is defined in the CXL 2.0 specification as
a way for the OS to get CXL specific information from the system
firmware.

CXL 2.0 specification adds an _HID, ACPI0016, for CXL capable host
bridges, with a _CID of PNP0A08 (PCIe host bridge). CXL aware software
is able to use this initiate the proper _OSC method, and get the _UID
which is referenced by the CEDT. Therefore the existence of an ACPI0016
device allows a CXL aware driver perform the necessary actions. For a
CXL capable OS, this works. For a CXL unaware OS, this works.

CEDT awaremess requires more. The motivation for ACPI0017 is to provide
the possibility of having a Linux CXL module that can work on a legacy
Linux kernel. Linux core PCI/ACPI which won't be built as a module,
will see the _CID of PNP0A08 and bind a driver to it. If we later loaded
a driver for ACPI0016, Linux won't be able to bind it to the hardware
because it has already bound the PNP0A08 driver. The ACPI0017 device is
an opportunity to have an object to bind a driver will be used by a
Linux driver to walk the CXL topology and do everything that we would
have preferred to do with ACPI0016.

There is another motivation for an ACPI0017 device which isn't
implemented here. An operating system needs an attach point for a
non-volatile region provider that understands cross-hostbridge
interleaving. Since QEMU emulation doesn't support interleaving yet,
this is more important on the OS side, for now.

As of CXL 2.0 spec, only 1 sub structure is defined, the CXL Host Bridge
Structure (CHBS) which is primarily useful for telling the OS exactly
where the MMIO for the host bridge is.

Link: https://lore.kernel.org/linux-cxl/20210115034911.nkgpzc756d6qmjpl@intel.com/T/#t
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220429144110.25167-26-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-05-13 06:13:36 -04:00
..
cxl_root_port.c hw/cxl/rp: Add a root port 2022-05-13 06:13:36 -04:00
dec.c Use OBJECT_DECLARE_SIMPLE_TYPE when possible 2020-09-18 14:12:32 -04:00
dec.h Include qemu-common.h exactly where needed 2019-06-12 13:20:20 +02:00
gen_pcie_root_port.c hw/pcie-root-port: Fix hotplug for PCI devices requiring IO 2021-08-03 16:31:07 -04:00
i82801b11.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
ioh3420.c Include migration/vmstate.h less 2019-08-16 13:31:52 +02:00
Kconfig hw/cxl/rp: Add a root port 2022-05-13 06:13:36 -04:00
meson.build hw/cxl/rp: Add a root port 2022-05-13 06:13:36 -04:00
pci_bridge_dev.c Use OBJECT_DECLARE_SIMPLE_TYPE when possible 2020-09-18 14:12:32 -04:00
pci_expander_bridge.c acpi/cxl: Create the CEDT (9.14.1) 2022-05-13 06:13:36 -04:00
pcie_pci_bridge.c Use OBJECT_DECLARE_SIMPLE_TYPE when possible 2020-09-18 14:12:32 -04:00
pcie_root_port.c hw/cxl/rp: Add a root port 2022-05-13 06:13:36 -04:00
simba.c Include qemu/module.h where needed, drop it from qemu-common.h 2019-06-12 13:18:33 +02:00
xio3130_downstream.c pci: expose TYPE_XIO3130_DOWNSTREAM name 2022-03-06 05:08:23 -05:00
xio3130_upstream.c pci-bridge/xio3130_upstream: Fix error handling 2022-03-06 05:08:23 -05:00