Volume 4: Base IA-32 Instruction Reference
4:389
WRMSR—Write to Model Specific Register
Description
Writes the contents of registers EDX:EAX into the 64-bit model specific register (MSR)
specified in the ECX register. The high-order 32 bits are copied from EDX and the
low-order 32 bits are copied from EAX. Always set undefined or reserved bits in an MSR
to the values previously read.
This instruction must be executed at privilege level 0 or in real-address mode;
otherwise, a general protection exception #GP(0) will be generated. Specifying a
reserved or unimplemented MSR address in ECX will also cause a general protection
exception.
When the WRMSR instruction is used to write to an MTRR, the TLBs are invalidated,
including the global entries see the
Intel Architecture Software Developer’s Manual,
Volume 3
).
The MSRs control functions for testability, execution tracing, performance-monitoring
and machine check errors. See model-specific instructions for all the MSRs that can be
written to with this instruction and their addresses.
The WRMSR instruction is a serializing instruction.
The CPUID instruction should be used to determine whether MSRs are supported
(EDX[5]=1) before using this instruction.
Operation
IF Itanium System Environment THEN IA-32_Intercept(INST,WRMSR);
MSR[ECX]
EDX:EAX;
Flags Affected
None.
Additional Itanium System Environment Exceptions
IA-32_Intercept
Mandatory Instruction Intercept.
Protected Mode Exceptions
#GP(0)
If the current privilege level is not 0.
If the value in ECX specifies a reserved or unimplemented MSR
address.
Real Address Mode Exceptions
#GP
If the current privilege level is not 0
If the value in ECX specifies a reserved or unimplemented MSR
address.
Opcode
Instruction
Description
0F 30
WRMSR
Write the value in EDX:EAX to MSR specified by ECX
Содержание ITANIUM ARCHITECTURE
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Страница 288: ...Volume 4 Base IA 32 Instruction Reference 4 281 LSS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 352: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Страница 368: ...Volume 4 Base IA 32 Instruction Reference 4 361 SHL SHR Shift Instructions See entry for SAL SAR SHL SHR ...
Страница 373: ...4 366 Volume 4 Base IA 32 Instruction Reference SIDT Store Interrupt Descriptor Table Register See entry for SGDT SIDT ...
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Страница 590: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
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Страница 603: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...
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