The previous code did not pass the current thread
to sched_unblock, even though the CFS scheduler requires
access to the current thread to update vruntime before
making a preemption decision.

We now pass the current thread, but we also ensure that
the current ready queue is locked, allowing the scheduler
safe access to the metadata in the ready queue.

fix `choose_cpu_for_new_thread` to fall back to CPU #0 if
called early.

These are courtesy of John Ousterhout's commit:

https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commit;h=16c7d34d02045bc7e6165a13c549a7968e074d4b

from 2015 to 2021
- fsutil_ls must close the directory after reading it
- timer: Fix timer calibration logic.
- fsutil: Fix writing end-of-archive marker.
- rtc: Fix Unix epoch conversion from RTC time.
- modify the linker script to match the generated binary

https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commit;h=919347c164606c3f1544b2e8bd62f505aeda80a1
https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commit;h=85da529909adac7ed00861d259001b124cd5b54f
https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commitdiff;h=83855d769a0a09dd9f2bfdd74f1b5f8a23a1bd7e
https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commitdiff;h=52fd7eb25b15662abfacca92e20416cb29d85395
https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commitdiff;h=bb0485f5561709b2d9a97fdeda9bfa1bd55a20c9

This was missing from the previous MPP removal patch

This will make an E1000 network card available in Qemu/KVM

This function must be called for devices such as the E1000
that need to be able to access the PCI bus as master

This patch removes the xv6 code that reads that outdated
Multiprocessor specification (MPP) tables which Qemu has been
deprecating, and adds basic support for ACPI instead.
We read the RSDT and MADT in particular to find out
- local APIC base address
- number of processors and the APIC id
- I/O APIC base address and id

The LAPIC and IOAPIC support files have been changes to use
the information obtained.

Tested with Qemu, Qemu/KVM, Bochs, and Bochs/SMP.
Based on ACPI 6.3 from 2019.

The changes to the boot loader were contributed by
Jamie Whiting.  This patch also contains the following:

- 2-level physical allocator
- self tests for the allocator
- reworking of virtual address space layout
- no longer made boot page table user-accessible
- various small fixes
  + fixed -ul= flag which previously didn't work
  + fixed -rs= flag

This patch avoids the wrong applications of rules when running
make -j grade.  Previously, this resulted in redundant failing
runs that took time and left files such as .error and .output
around.

These self tests were somehow lost when I merged Lance's
original work.  This fix restores them so that 'make grade'
in the self test directory works

- also fixed warnings in malicious test

- See README.md for details.
- made pintos able to run multiple bochs at the same time
- tweaks to AP startup code

- also separate disks to allow `make -j grade` for extended filesystem
  tests

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105051

also fixed warnings

These changes make Pintos work with Qemu 6.2.0 as of Spring '22
See https://lists.nongnu.org/archive/html/qemu-discuss/2022-01/msg00036.html