Joerg Roedel

The issue is related to the I/O page fault handler in the Linux kernel, which currently locates the PCI device by calling `pci get domain bus and slot()`. This function searches the list of all PCI devices until the desired device is found. To improve lookup efficiency, it is replaced with `device rbtree find()` to search the device within the probed device rbtree. The I/O page fault is initiated by the device, which does not have any synchronization mechanism with the software to ensure that the device stays in the probed device tree. Theoretically, a device could be released by the IOMMU subsystem after `device rbtree find()` and before `iopf get dev fault param()`, which would cause a use-after-free problem. A mutex is added to synchronize the I/O page fault reporting path and the IOMMU release device path.

The issue arises when memory marked as EFI boot services data is not properly mapped as encrypted under SEV, potentially leading to a kernel crash at boot. This occurs because some drivers require memory to be preserved after ExitBootServices() by inserting a new EFI memory descriptor and marking it with the EFI MEMORY RUNTIME attribute. The kernel needs to map this memory encrypted to prevent crashes. The ` ioremap check other()` function has been expanded to check for this type of boot data reserved at runtime and indicate that it should be mapped encrypted for an SEV guest.