XRSTOR

Restore Processor Extended States

참고 사항

Instruction Operand Encoding

Description

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(R) 64 and IA-32 Architectures Soft-ware Developer's Manual, Volume 1.

Section 13.8, "Operation of XRSTOR," of Intel(R) 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:

• Execution of XRSTOR may take one of two forms: standard and compacted. Bit 63 of the XCOMPBV field in the XSAVE header determines which form is used: value 0 specifies the standard form, while value 1 specifies the compacted form.\esc{} If RFBM[i] = 0, XRSTOR does not update state component i.¹

• If RFBM[i] = 1 and bit i is clear in the XSTATEBV field in the XSAVE header, XRSTOR initializes state component i.

• If RFBM[i] = 1 and XSTATEBV[i] = 1, XRSTOR loads state component i from the XSAVE area.

• The standard form of XRSTOR treats MXCSR (which is part of state component 1 -- SSE) differently from the XMM registers. If either form attempts to load MXCSR with an illegal value, a general-protection exception (#GP) occurs.

• XRSTOR loads the internal value XRSTORINFO, which may be used to optimize a subsequent execution of XSAVEOPT or XSAVES.

• Immediately following an execution of XRSTOR, the processor tracks as in-use (not in initial configuration) any state component i for which RFBM[i] = 1 and XSTATEBV[i] = 1; it tracks as modified any state component i for which RFBM[i] = 0.

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.

Operation

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;

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[bit1]= 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 <- < CPL,VMXNR,LAXA,COMPMASK> ;

Flags Affected

None.

Intel C/C++ Compiler Intrinsic Equivalent

XRSTOR : void _xrstor(void*, unsigned __int64);
XRSTOR : void _xrstor64(void*, unsigned __int64);

Protected Mode Exceptions

#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).

Real-Address Mode Exceptions

#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.

Virtual-8086 Mode Exceptions

Same exceptions as in protected mode

Compatibility Mode Exceptions

Same exceptions as in protected mode.

64-Bit Mode Exceptions

#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).

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