In the Linux kernel, the following vulnerability has been resolved: x86/kvm: Force legacy PCI hole to UC when overriding MTRRs for TDX/SNP When running as an SNP or TDX guest under KVM, force the legacy PCI hole, i.e. memory between Top of Lower Usable DRAM and 4GiB, to be mapped as UC via a forced variable MTRR range. In most KVM-based setups, legacy devices such as the HPET and TPM are enumerated via ACPI. ACPI enumeration includes a Memory32Fixed entry, and optionally a SystemMemory descriptor for an OperationRegion, e.g. if the device needs to be accessed via a Control Method. If a SystemMemory entry is present, then the kernel's ACPI driver will auto-ioremap the region so that it can be accessed at will. However, the ACPI spec doesn't provide a way to enumerate the memory type o