XSAVEXGETBV

XSAVEXGETBV is an informal term used to describe a sequence of low-level processor state management operations that combines the XSAVE family of instructions with the XGETBV instruction. While not an official opcode or single instruction, the term is used in some technical discussions to refer to the coordinated use of saving extended processor state and querying or configuring which state components are enabled on a system. The concept is relevant to operating system kernels, hypervisors, and other software that must manage hardware state across context switches, interrupts, or VM exits.

XSAVE refers to a set of instructions (including XSAVE, XSAVEC, XSAVEOPT, and related variants) that save the processor’s extended state to a memory area defined by the operating system. This extended state includes features such as SSE, AVX, AVX-512, and other XSTATE components, as described by the XSTATE model. The memory save area must be properly allocated and aligned, and the set of components saved is governed by the XCR0 control register.

XGETBV reads the contents of the extended control register XCR0, typically to determine which state components are currently enabled and whether the operating system has configured the CPU to save and restore those components. To enable additional features, software may use XSETBV to write a desired value to XCR0.

In practice, a system implementing XSAVEXGETBV would first use CPUID to determine feature support, call XGETBV to inspect XCR0, use XSETBV to enable needed components, and then perform XSAVE operations to preserve the active state. This pattern is central to enabling advanced vector extensions in a controlled, portable way. See also XSTATE, XGETBV, XSETBV, XSAVE, and XRSTOR.