CVE-2024-26761

In the Linux kernel, the following vulnerability has been resolved:

cxl/pci: Fix disabling memory if DVSEC CXL Range does not match a CFMWS window

The Linux CXL subsystem is built on the assumption that HPA == SPA. That is, the host physical address (HPA) the HDM decoder registers are programmed with are system physical addresses (SPA).

During HDM decoder setup, the DVSEC CXL range registers (cxl-3.1, 8.1.3.8) are checked if the memory is enabled and the CXL range is in a HPA window that is described in a CFMWS structure of the CXL host bridge (cxl-3.1, 9.18.1.3).

Now, if the HPA is not an SPA, the CXL range does not match a CFMWS window and the CXL memory range will be disabled then. The HDM decoder stops working which causes system memory being disabled and further a system hang during HDM decoder initialization, typically when a CXL enabled kernel boots.

Prevent a system hang and do not disable the HDM decoder if the decoder's CXL range is not found in a CFMWS window.

Note the change only fixes a hardware hang, but does not implement HPA/SPA translation. Support for this can be added in a follow on patch series.