PTWRITE

PTWRITE — Write Data to a Processor Trace Packet

Opcode/Instruction	Op/En	64/32 bit Mode Support	CPUID Feature Flag	Description
F3 REX.W 0F AE /4 PTWRITE r64/m64	RM	V/N.E		Reads the data from r64/m64 to encode into a PTW packet if dependencies are met (see details below).
F3 0F AE /4 PTWRITE r32/m32	RM	V/V		Reads the data from r32/m32 to encode into a PTW packet if dependencies are met (see details below).

Instruction Operand Encoding ¶

Op/En	Operand 1	Operand 2	Operand 3	Operand 4
RM	ModRM:rm (r)	NA	NA	NA

Description ¶

This instruction reads data in the source operand and sends it to the Intel Processor Trace hardware to be encoded in a PTW packet if TriggerEn, ContextEn, FilterEn, and PTWEn are all set to 1. For more details on these values, see Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3C, Section 35.2.2, “Software Trace Instrumentation with PTWRITE”. The size of data is 64-bit if using REX.W in 64-bit mode, otherwise 32-bits of data are copied from the source operand.

Note: The instruction will #UD if prefix 66H is used.

Operation ¶

IF (IA32_RTIT_STATUS.TriggerEn & IA32_RTIT_STATUS.ContextEn & IA32_RTIT_STATUS.FilterEn & IA32_RTIT_CTL.PTWEn) = 1
    PTW.PayloadBytes ← Encoded payload size;
    PTW.IP ← IA32_RTIT_CTL.FUPonPTW
    IF IA32_RTIT_CTL.FUPonPTW = 1
        Insert FUP packet with IP of PTWRITE;
    FI;
FI;

Flags Affected ¶

None.

Other Exceptions ¶

#GP(0)	If a memory operand effective address is outside the CS, DS, ES, FS or GS segments.
#SS(0)	If a memory operand effective address is outside the SS segment limit.
#PF	(fault-code) For a page fault.
#AC(0)	If an unaligned memory reference is made while the current privilege level is 3 and alignment checking is enabled.
#UD	If CPUID.(EAX=14H, ECX=0):EBX.PTWRITE [Bit 4] = 0.
	If LOCK prefix is used.
	If 66H prefix is used.

Real-Address Mode Exceptions ¶

#GP(0)	If any part of the operand lies outside of the effective address space from 0 to 0FFFFH.
#SS(0)	If a memory operand effective address is outside the SS segment limit.
#UD	If CPUID.(EAX=14H, ECX=0):EBX.PTWRITE [Bit 4] = 0.
	If LOCK prefix is used.
	If 66H prefix is used.

Virtual 8086 Mode Exceptions ¶

#GP(0)	If any part of the operand lies outside of the effective address space from 0 to 0FFFFH.
#SS(0)	If a memory operand effective address is outside the SS segment limit.
#PF	(fault-code) For a page fault.
#AC(0)	If an unaligned memory reference is made while alignment checking is enabled.
#UD	If CPUID.(EAX=14H, ECX=0):EBX.PTWRITE [Bit 4] = 0.
	If LOCK prefix is used.
	If 66H prefix is used.

Compatibility Mode Exceptions ¶

Same exceptions as in Protected Mode.

64-Bit Mode Exceptions ¶

#GP(0)	If the memory address is in a non-canonical form.
#SS(0)	If a memory address referencing the SS segment is in a non-canonical form.
#PF	(fault-code) For a page fault.
#AC(0)	If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
#UD	If CPUID.(EAX=14H, ECX=0):EBX.PTWRITE [Bit 4] = 0.
	If LOCK prefix is used.
	If 66H prefix is used.