x86-64 PCID and PMU Support

[evanstella]

Summary of this Pull Request (PR)

This PR is for an initial review of PCID support. This is not ready to be pulled but will need to be integrated with the namespace implementation that is being developed right now.

This PR adds support for PCID, a kernel API for using PCID for an ASID implementation, as well as PMU programming support for Intel's hardware PMU.

Particularly, I'd like your opinion on:

• the kernel ASID API and whether it makes sense
• The updated context switch code (chal_pgtbl_update())
• (less important) The PMU programming API and whether this is actually an addition we would want to add to the kernel API

Intent for your PR

Choose one (Mandatory):

• [x] This PR is for a code-review and is intended to get feedback, but not to be pulled yet.
• [ ] This PR is mature, and ready to be integrated into the repo.

Reviewers (Mandatory):

@gparmer

Code Quality

As part of this pull request, I've considered the following:

Style:

• [x] Comments adhere to the Style Guide (SG)
• [x] Spacing adhere's to the SG
• [x] Naming adhere's to the SG
• [x] All other aspects of the SG are adhered to, or exceptions are justified in this pull request
• [ ] I have run the auto formatter on my code before submitting this PR (see doc/auto_formatter.md for instructions)

Code Craftsmanship:

• [x] I've made an attempt to remove all redundant code
• [x] I've considered ways in which my changes might impact existing code, and cleaned it up
• [x] I've formatted the code in an effort to make it easier to read (proper error handling, function use, etc...)
• [x] I've commented appropriately where code is tricky
• [x] I agree that there is no "throw-away" code, and that code in this PR is of high quality

Testing

I've tested the code using the following test programs (provide list here):

• [ ] micro_booter
• [x] unit_pingpong
• [x] unit_schedtests
• [x] All test outlined in the x86-64 patch

[gparmer]

You do need to add logic into pgtbl_deactivate to remove the asid from the per-cpu table. We need to discuss this as we might be deactivating on a different core than that on which the component executed.