hwpmc: add the LBR capability and multipart record type

[afscoelho_gmail.com]

Summary

Add PMC_CAP_LBR and the PMC_CC_MULTIPART_LBR record type. Make
struct pmc_multipart big enough for 16 branch records, and bump
PMC_VERSION_MINOR.

Depends on D60565 and D58698

Test Plan

Built amd64 GENERIC + hwpmc.ko, GENERIC without HWPMC_HOOKS, and arm64.
Ran tests/sys/pmc on AMD Zen 6 (LBR v2).

[afscoelho_gmail.com]

Rebase only. No code change.

[ali_mashtizadeh.com]

I can fix the flag issue and we land my diff and you rebase on top of my branch history interface.

I was thinking to generalize the callback interface so providers like ibs can use it too.

sys/sys/pmc.h

991

This is a problem because it’s on the stack and getting way too big. It’ll be even bigger for Intel and arm’s branch histories.

This is why my proposed branch history interface uses a callback mechanism so we can fill in the sample after allocation.

[afscoelho_gmail.com]

In D60566#1395553, @ali_mashtizadeh.com wrote:

I can fix the flag issue and we land my diff and you rebase on top of my branch history interface.

I was thinking to generalize the callback interface so providers like ibs can use it too.

Ali, thank you for the review. Yes, let us wait until your branch history interface lands and I will rebse on it. Just add me in the diff so that I can see when it lands, Thannks!

[ali_mashtizadeh.com]

@mhorne Can you review the other diff so we can rebase these on top and LBR in.