mirror of https://github.com/xemu-project/xemu.git
3d6a69b6eb
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> |
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| authz | ||
| block | ||
| chardev | ||
| crypto | ||
| disas | ||
| exec | ||
| fpu | ||
| hw | ||
| io | ||
| libdecnumber | ||
| migration | ||
| monitor | ||
| net | ||
| qapi | ||
| qemu | ||
| qom | ||
| scsi | ||
| semihosting | ||
| standard-headers | ||
| sysemu | ||
| tcg | ||
| ui | ||
| user | ||
| elf.h | ||
| glib-compat.h | ||
| qemu-io.h | ||
| qemu-main.h | ||