senduipi

Send User Inter-Processor Interrupt

SENDUIPI r64

Sends a User IPI to another processor.

Details

Sends a User Inter-Processor Interrupt (User IPI) to another processor identified by the UIPI index stored in the source 64-bit register. The source register contains an UPID (User IPI Posting Descriptor) index that identifies the target thread. Requires UINTR extension support; operation may be serializing and updates the target processor's interrupt state.

Pseudocode Operation

IF (!UINTR_enabled) THEN #UD;
uipi_index ← src_reg[63:0];
upid ← retrieve_UPID_from_index(uipi_index);
post_user_interrupt_to_target(upid);
SEND_IPI_TO_TARGET_CPU();

Example

SENDUIPI rax

Encoding

Binary Layout
F3
+0
0F
+1
C7
+2
ModRM
+3
 
Format Legacy
Opcode F3 0F C7 /6
Extension UINTR

Operands

  • dest
    64-bit general-purpose register (e.g. RAX)

Reference (Intel® SDM)

Instruction Forms

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

Instruction Operand Encoding

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

Description

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: • Bit 0: V, a valid bit. • Bits 7:1 are reserved and must be 0. • Bits 15:8: UV, the user-interrupt vector (in the range 0–63, so bits 15:14 must be 0). • Bits 63:16 are reserved. • Bits 127:64: UPIDADDR, the linear address of a user posted-interrupt descriptor (UPID). (UPIDADDR is 64byte aligned, so bits 69:64 of each UITTE must be 0.) Each UPID has the following format (fields and bits not referenced are reserved): • Bit 0 (ON) indicates an outstanding notification. If this bit is set, there is a notification outstanding for one or more user interrupts in PIR. • Bit 1 (SN) indicates that notifications should be suppressed. If this bit is set, agents (including SENDUIPI) should not send notifications when posting user interrupts in this descriptor. • Bits 23:16 (NV) contain the notification vector. This is used by agents sending user-interrupt notifications (including SENDUIPI). • Bits 63:32 (NDST) contain the notification destination. This is the target physical APIC ID (in xAPIC mode, bits 47:40 are the 8-bit APIC ID; in x2APIC mode, the entire field forms the 32-bit APIC ID). • Bits 127:64 (PIF) contain posted-interrupt requests. There is one bit for each user-interrupt vector. There is a user-interrupt request for a vector if the corresponding bit is 1. 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.

Operation

IF reg > UITTSZ;
THEN #GP(0);
FI;
read tempUITTE from 16 bytes at UITTADDR+ (reg « 4);
IF tempUITTE.V = 0 or tempUITTE sets any reserved bit
THEN #GP(0);
FI;


SENDUIPI—Send User Interprocessor Interrupt                                                                                                  Vol. 2B 4-619
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
FI;
tempUPID.PIR[tempUITTE.UV] := 1;
IF tempUPID.SN = tempUPID.ON = 0
THEN
tempUPID.ON := 1;
sendNotify := 1;
ELSE sendNotify := 0;
FI;
write tempUPID to 16 bytes at tempUITTE.UPIDADDR;// release lock
IF sendNotify = 1
THEN
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];
FI;
FI;

Flags Affected

None.

Exceptions

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.00H:EDX.UINTR[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. SENDUIPI—Send User Interprocessor Interrupt Vol. 2B 4-620