Does LBR_SELECT apply to BTF?

[tarmeneldur]

Hi all,

Very simple question: does the new LBR_SELECT branch filtering capability (introduced in Nehalem) also apply to the BTF branch single-stepping or just LBR (Last Branch Record tracing)? The naming of the feature suggests the later, but I just wanted to make sure.

Being able to single-step in selected classes of branches (as opposed to all of them) would help me a lot with the work that I am doing.

Thanks in advance.

[SHIH_K_Intel]

I don't believe so.
Typical usage of LBR is profiling, when the instruction stream is progressing normally, and a stack of LBR can capture branch addresses over a larger window of ip addresses. If you are already single-stepping, historical branch addressescould be captured bythe tool already withoutusing additional facility in the cpu hardware.

[tarmeneldur]

I see. Do you know if this is also the case with BTS (Branch Trace Store), meaning, can we use LBR_SELECT to filter out which branch record are saved to the BTS buffer in memory?

Thanks again,