SENDUIPI — Send User Interprocessor Interrupt

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
F3 0F C7 /6 SENDUIPI reg A V/I UINTR Send interprocessor user interrupt.

Instruction Operand Encoding

Op/En Tuple Operand 1 Operand 2 Operand 3 Operand 4
A N/A ModRM:reg (r) N/A N/A N/A


The SENDUIPI instruction sends the user interprocessor interrupt (IPI) indicated by its register operand. (The operand always has 64 bits; operand-size overrides such as the prefix 66 are ignored.)

SENDUIPI uses a data structure called the user-interrupt target table (UITT). This table is located at the linear address UITTADDR (in the IA32_UINTR_TT MSR); it comprises UITTSZ+1 16-byte entries, where UITTSZ = IA32_UINT_MISC[31:0]. SENDUIPI uses the UITT entry (UITTE) indexed by the instruction's register operand. Each UITTE has the following format:

Each UPID has the following format (fields and bits not referenced are reserved):

Although SENDUIPI may be executed at any privilege level, all of the instruction’s memory accesses (to a UITTE and a UPID) are performed with supervisor privilege.

SENDUIPI sends a user interrupt by posting a user interrupt with vector V in the UPID referenced by UPIDADDR and then sending, as an ordinary IPI, any notification interrupt specified in that UPID.


IF reg > UITTSZ;
    THEN #GP(0);
read tempUITTE from 16 bytes at UITTADDR+ (reg « 4);
IF tempUITTE.V = 0 or tempUITTE sets any reserved bit
    THEN #GP(0);
read tempUPID from 16 bytes at tempUITTE.UPIDADDR;// under lock
IF tempUPID sets any reserved bits or bits that must be zero
    THEN #GP(0); // release lock
tempUPID.PIR[tempUITTE.UV] := 1;
IF tempUPID.SN = tempUPID.ON = 0
        tempUPID.ON := 1;
        sendNotify := 1;
    ELSE sendNotify := 0;
write tempUPID to 16 bytes at tempUITTE.UPIDADDR;// release lock
IF sendNotify = 1
        IF local APIC is in x2APIC mode
            THEN send ordinary IPI with vector tempUPID.NV
                to 32-bit physical APIC ID tempUPID.NDST;
            ELSE send ordinary IPI with vector tempUPID.NV
                to 8-bit physical APIC ID tempUPID.NDST[15:8];

Flags Affected


Protected Mode Exceptions

#UD The SENDUIPI instruction is not recognized in protected mode.

Real-Address Mode Exceptions

#UD The SENDUIPI instruction is not recognized in real-address mode.

Virtual-8086 Mode Exceptions

#UD The SENDUIPI instruction is not recognized in virtual-8086 mode.

Compatibility Mode Exceptions

#UD The SENDUIPI instruction is not recognized in compatibility mode.

64-Bit Mode Exceptions

#UD If the LOCK prefix is used.
If executed inside an enclave.
If CR4.UINTR = 0.
If IA32_UINTR_TT[0] = 0.
If CPUID.07H.0H:EDX.UINTR[bit 5] = 0.
#PF If a page fault occurs.
#GP If the value of the register operand exceeds UITTSZ.
If the selected UITTE is not valid or sets any reserved bits.
If the selected UPID sets any reserved bits.
If there is an attempt to access memory using a linear address that is not canonical relative to the current paging mode.