| Opcode | Instruction | Op/En | 64-Bit Mode | Compat/Leg Mode | Description |
|---|---|---|---|---|---|
| 0F C7 /5 | XSAVES mem | M | Valid | Valid | Save state components specified by EDX:EAX to mem with compaction, optimizing if possible. |
| REX.W+ 0F C7 /5 | XSAVES64 mem | M | Valid | N.E. | Save state components specified by EDX:EAX to mem with compaction, optimizing if possible. |
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| M | ModRM:r/m (w) | NA | NA | NA |
Performs a full or partial save of processor state components to the XSAVE area located at the memory address specified by the destination operand. The implicit EDX:EAX register pair specifies a 64-bit instruction mask. The specific state components saved correspond to the bits set in the requested-feature bitmap (RFBM), the logical-AND of EDX:EAX and the logical-OR of XCR0 with the IA32_XSS MSR. XSAVES may be executed only if CPL = 0.
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 13.11, “Operation of XSAVES,” of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1 provides a detailed description of the operation of the XSAVES instruction. The following items provide a high-level outline:
Use of a destination operand not aligned to 64-byte boundary (in either 64-bit or 32-bit modes) results in a general-protection (#GP) exception. In 64-bit mode, the upper 32 bits of RDX and RAX are ignored.
1.
There is an exception for state component 1 (SSE). MXCSR is part of SSE state, but XINUSE[1] may be 0 even if MXCSR does not have its initial value of 1F80H. In this case, the init optimization does not apply and XSAVEC will save SSE state as long as RFBM[1] = 1 and the modified optimization is not being applied.
2.
There is an exception for state component 1 (SSE). MXCSR is part of SSE state, but XINUSE[1] may be 0 even if MXCSR does not have its initial value of 1F80H. In this case, XSAVES sets XSTATE_BV[1] to 1 as long as RFBM[1] = 1.
RFBM ← (XCR0 OR IA32_XSS) AND EDX:EAX;
/* bitwise logical OR and AND */
IF in VMX non-root operation
THEN VMXNR ← 1;
ELSE VMXNR ← 0;
FI;
LAXA ← linear address of XSAVE area;
COMPMASK ← RFBM OR 80000000_00000000H;
IF XRSTOR_INFO = (cid:162)CPL,VMXNR,LAXA,COMPMASK(cid:178)
THEN MODOPT ← 1;
ELSE MODOPT ← 0;
FI;
IF RFBM[0] = 1 and XINUSE[0] = 1
THEN store x87 state into legacy region of XSAVE area;
/* might avoid saving if x87 state is not modified and MODOPT = 1 */
FI;
IF RFBM[1] = 1 and (XINUSE[1] = 1 or MXCSR ≠ 1F80H)
THEN store SSE state into legacy region of XSAVE area;
/* might avoid saving if SSE state is not modified and MODOPT = 1 */
FI;
IF RFBM[2] = 1 AND XINUSE[2] = 1
THEN store AVX state into extended region of XSAVE area;
/* might avoid saving if AVX state is not modified and MODOPT = 1 */
FI;
XSTATE_BV field in XSAVE header ← XINUSE AND RFBM;1
XCOMP_BV field in XSAVE header ← COMPMASK;
None.
XSAVES: void _xsaves( void * , unsigned __int64); XSAVES64: void _xsaves64( 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. |
| #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 or CPUID.(EAX=0DH,ECX=1):EAX.XSS[bit 3] = 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 |
1.
| If MXCSR does not have its initial value of 1F80H, XSAVES sets XSTATE_BV[1] to 1 as long as RFBM[1] = 1, regardless of the value |
| of XINUSE[1]. |
| 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. |
| #NM | If CR0.TS[bit 3] = 1. |
| #UD |
If CPUID.01H:ECX.XSAVE[bit 26] = 0 or CPUID.(EAX=0DH,ECX=1):EAX.XSS[bit 3] = 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 the memory address is in a non-canonical form. If a memory operand is not aligned on a 64-byte boundary, regardless of segment. |
| #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 or CPUID.(EAX=0DH,ECX=1):EAX.XSS[bit 3] = 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). |