On 8/5/26 6:15 PM, Sohil Mehta wrote: > Linear Address Space Separation (LASS) is a security feature that blocks > accesses across the user/kernel boundary based on bit 63 of the linear > address alone, before any page walk is performed. Host support for LASS > has been merged [1][2]. This series adds the KVM virtualization support. > I tested this series on Sierra Forest, using the QEMU support linked below to expose LASS to the guest.
Covered: - Guest enumeration of LASS and enabling of CR4.LASS. - User accesses to supervisor addresses on hardware and under the forced emulation prefix. - Supervisor accesses to user addresses from a guest kernel module under the forced emulation prefix: reads and writes, RFLAGS.AC suppression, SMAP=0 behavior, implicit descriptor-table accesses, and violations at a branch target. - Nested VMX: VMCLEAR with a low operand address, taking a #GP at RFLAGS.AC=0 and completing at AC=1, via get_vmx_mem_address() -> vmx_is_lass_violation(). Not covered: the TSS I/O bitmap paths in patch 2, and ENCLS. QEMU changes to expose LASS to guests: https://lore.kernel.org/all/[email protected]/ Tested-by: Kishen Maloor <[email protected]>
