| Opcode | Instruction | Op/En | 64-Bit Mode | Compat/Leg Mode | Description |
|---|---|---|---|---|---|
| 0F AE /5 | XRSTOR mem | M | Valid | Valid | Restore state components specified by EDX:EAX from mem. |
| REX.W+ 0F AE /5 | XRSTOR64 mem | M | Valid | N.E. | Restore state components specified by EDX:EAX from mem. |
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| M | ModRM:r/m (r) | NA | NA | NA |
Performs a full or partial restore of processor state components from the XSAVE area located at the memory address specified by the source operand. The implicit EDX:EAX register pair specifies a 64-bit instruction mask. The specific state components restored correspond to the bits set in the requested-feature bitmap (RFBM), which is the logical-AND of EDX:EAX and XCR0.
The format of the XSAVE area is detailed in Section 13.4, “XSAVE Area,” of Intel® 64 and IA-32 Architectures Soft-ware Developer’s Manual, Volume 1.
Section 13.8, “Operation of XRSTOR,” of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1 provides a detailed description of the operation of the XRSTOR instruction. The following items provide a high-level outline:
for which RFBM[i] = 0.
i
Use of a source operand not aligned to 64-byte boundary (for 64-bit and 32-bit modes) results in a general-protec-tion (#GP) exception. In 64-bit mode, the upper 32 bits of RDX and RAX are ignored.
RFBM ← XCR0 AND EDX:EAX;
/* bitwise logical AND */
COMPMASK ← XCOMP_BV field from XSAVE header;
RSTORMASK ← XSTATE_BV field from XSAVE header;
IF in VMX non-root operation
THEN VMXNR ← 1;
1.
There is an exception if RFBM[1] = 0 and RFBM[2] = 1. In this case, the standard form of XRSTOR will load MXCSR from memory, even though MXCSR is part of state component 1 — SSE. The compacted form of XRSTOR does not make this exception.
ELSE VMXNR ← 0;
FI;
LAXA ← linear address of XSAVE area;
IF COMPMASK[63] = 0
THEN
/* Standard form of XRSTOR */
If RFBM[0] = 1
THEN
IF RSTORMASK[0] = 1
THEN load x87 state from legacy region of XSAVE area;
ELSE initialize x87 state;
FI;
FI;
If RFBM[1] = 1
THEN
IF RSTORMASK[1] = 1
THEN load XMM registers from legacy region of XSAVE area;
ELSE set all XMM registers to 0;
FI;
FI;
If RFBM[2] = 1
THEN
IF RSTORMASK[2] = 1
THEN load AVX state from extended region (standard format) of XSAVE area;
ELSE initialize AVX state;
FI;
FI;
If RFBM[1] = 1 or RFBM[2] = 1
THEN load MXCSR from legacy region of XSAVE area;
FI;
FI;
ELSE
/* Compacted form of XRSTOR */
IF CPUID.(EAX=0DH,ECX=1):EAX.XSAVEC[bit 1] = 0
THEN
/* compacted form not supported */
#GP(0);
FI;
If RFBM[0] = 1
THEN
IF RSTORMASK[0] = 1
THEN load x87 state from legacy region of XSAVE area;
ELSE initialize x87 state;
FI;
FI;
If RFBM[1] = 1
THEN
IF RSTORMASK[1] = 1
THEN load SSE state from legacy region of XSAVE area;
ELSE initialize SSE state;
FI;
FI;
If RFBM[2] = 1
THEN
IF RSTORMASK[2] = 1
THEN load AVX state from extended region (compacted format) of XSAVE area;
ELSE initialize AVX state;
FI;
FI;
FI;
XRSTOR_INFO ← (cid:162)CPL,VMXNR,LAXA,COMPMASK(cid:178);
None.
XRSTOR:
void _xrstor( void * , unsigned __int64);
XRSTOR:
void _xrstor64( void * , unsigned __int64);
| #GP(0) |
If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If a memory operand is not aligned on a 64-byte boundary, regardless of segment. If bit 63 of the XCOMP_BV field of the XSAVE header is 1 and CPUID.(EAX=0DH,ECX=1):EAX.XSAVEC[bit 1] = 0. If the standard form is executed and a bit in XCR0 is 0 and the corresponding bit in the XSTATE_BV field of the XSAVE header is 1. If the standard form is executed and bytes 23:8 of the XSAVE header are not all zero. If the compacted form is executed and a bit in XCR0 is 0 and the corresponding bit in the XCOMP_BV field of the XSAVE header is 1. If the compacted form is executed and a bit in the XCOMP_BV field in the XSAVE header is 0 and the corresponding bit in the XSTATE_BV field is 1. If the compacted form is executed and bytes 63:16 of the XSAVE header are not all zero. If attempting to write any reserved bits of the MXCSR register with 1. |
| #SS(0) | If a memory operand effective address is outside the SS segment limit. |
| #PF(fault-code) | If a page fault occurs. |
| #NM | If CR0.TS[bit 3] = 1. |
| #UD |
If CPUID.01H:ECX.XSAVE[bit 26] = 0. If CR4.OSXSAVE[bit 18] = 0. If any of the LOCK, 66H, F3H or F2H prefixes is used. |
| #AC | If this exception is disabled a general protection exception (#GP) is signaled if the memory operand is not aligned on a 16-byte boundary, as described above. If the alignment check exception (#AC) is enabled (and the CPL is 3), signaling of #AC is not guaranteed and may vary with implementation, as follows. In all implementations where #AC is not signaled, a general protection exception is signaled in its place. In addition, the width of the alignment check may also vary with implementation. For instance, for a given implementation, an align-ment check exception might be signaled for a 2-byte misalignment, whereas a general protec-tion exception might be signaled for all other misalignments (4-, 8-, or 16-byte misalignments). |
| #GP |
If a memory operand is not aligned on a 64-byte boundary, regardless of segment. If any part of the operand lies outside the effective address space from 0 to FFFFH. If bit 63 of the XCOMP_BV field of the XSAVE header is 1 and CPUID.(EAX=0DH,ECX=1):EAX.XSAVEC[bit 1] = 0. If the standard form is executed and a bit in XCR0 is 0 and the corresponding bit in the XSTATE_BV field of the XSAVE header is 1. If the standard form is executed and bytes 23:8 of the XSAVE header are not all zero. If the compacted form is executed and a bit in XCR0 is 0 and the corresponding bit in the XCOMP_BV field of the XSAVE header is 1. If the compacted form is executed and a bit in the XCOMP_BV field in the XSAVE header is 0 and the corresponding bit in the XSTATE_BV field is 1. If the compacted form is executed and bytes 63:16 of the XSAVE header are not all zero. If attempting to write any reserved bits of the MXCSR register with 1. |
| #NM | If CR0.TS[bit 3] = 1. |
| #UD |
If CPUID.01H:ECX.XSAVE[bit 26] = 0. If CR4.OSXSAVE[bit 18] = 0. If any of the LOCK, 66H, F3H or F2H prefixes is used. |
Same exceptions as in protected mode
Same exceptions as in protected mode.
| #GP(0) |
If a memory address is in a non-canonical form. If a memory operand is not aligned on a 64-byte boundary, regardless of segment. If bit 63 of the XCOMP_BV field of the XSAVE header is 1 and CPUID.(EAX=0DH,ECX=1):EAX.XSAVEC[bit 1] = 0. If the standard form is executed and a bit in XCR0 is 0 and the corresponding bit in the XSTATE_BV field of the XSAVE header is 1. If the standard form is executed and bytes 23:8 of the XSAVE header are not all zero. If the compacted form is executed and a bit in XCR0 is 0 and the corresponding bit in the XCOMP_BV field of the XSAVE header is 1. If the compacted form is executed and a bit in the XCOMP_BV field in the XSAVE header is 0 and the corresponding bit in the XSTATE_BV field is 1. If the compacted form is executed and bytes 63:16 of the XSAVE header are not all zero. If attempting to write any reserved bits of the MXCSR register with 1. |
| #SS(0) | If a memory address referencing the SS segment is in a non-canonical form. |
| #PF(fault-code) | If a page fault occurs. |
| #NM | If CR0.TS[bit 3] = 1. |
| #UD |
If CPUID.01H:ECX.XSAVE[bit 26] = 0. If CR4.OSXSAVE[bit 18] = 0. If any of the LOCK, 66H, F3H or F2H prefixes is used. |
| #AC | If this exception is disabled a general protection exception (#GP) is signaled if the memory operand is not aligned on a 16-byte boundary, as described above. If the alignment check exception (#AC) is enabled (and the CPL is 3), signaling of #AC is not guaranteed and may vary with implementation, as follows. In all implementations where #AC is not signaled, a general protection exception is signaled in its place. In addition, the width of the alignment check may also vary with implementation. For instance, for a given implementation, an align-ment check exception might be signaled for a 2-byte misalignment, whereas a general protec-tion exception might be signaled for all other misalignments (4-, 8-, or 16-byte misalignments). |