Comment 0 for bug 1782207

The PEBS(Processor Event Based Sampling) facility allows software to profile workload behavior by periodically capturing machine state, memory access information and other groups of architectural information. In native systems, PEBS uses a debug store mechanism to store a set of architectural state information for the processor and we need to specify a linear pages for the output buffer which must be pinned to physical pages. In virtualized systems, pinning the platform physical pages for the output buffer is difficult.
 PT V4 provide a method to format PEBS sampling data to new type of trace packet and output to Intel Processor Trace buffer. This depend on PT-VMX(Enabling use of EPT to redirect PT output)which enabled in ICX platform.
 Need modify in KVM and Qemu.

Intel Processor Trace v4 task list:
◾PT VMX which is done and in upstream phase, and need more review and update effort
◾PEBS via PT on SNR. It's new added task, which target to ww48
◾PT PEBS/EMON integration. This feature allows PEBS data to be written into PT output channel, leveraging PT Virtualization work for PEBS.
◾cpuid support and context switch
◾Support host-guest mode and system mode
 More Open feature includes Live Migration support and LBR support

Upstream target Linux 4.20