[0/6] x86: Expose consistent topology to guests

Message

Alejandro Vallejo Jan. 9, 2024, 3:38 p.m. UTC

Current topology handling is close to non-existent. As things stand, APIC
IDs are allocated through the apic_id=vcpu_id*2 relation without giving any
hints to the OS on how to parse the x2APIC ID of a given CPU and assuming
the guest will assume 2 threads per core.

This series involves bringing x2APIC IDs into the migration stream, so
older guests keep operating as they used to and enhancing Xen+toolstack so
new guests get topology information consistent with their x2APIC IDs. As a
side effect of this, x2APIC IDs are now packed and don't have (unless under
a pathological case) gaps.

Further work ought to allow combining this topology configurations with
gang-scheduling of guest hyperthreads into affine physical hyperthreads.
For the time being it purposefully keeps the configuration of "1 socket" +
"1 thread per core" + "1 core per vCPU".

Patch 1: Includes x2APIC IDs in the migration stream. This allows Xen to
         reconstruct the right x2APIC IDs on migrated-in guests, and
         future-proofs itself in the face of x2APIC ID derivation changes.
Patch 2: Minor refactor to expose xc_cpu_policy in libxl
Patch 3: Refactors xen/lib/x86 to work on non-Xen freestanding environments
         (e.g: hvmloader)
Patch 4: Remove old assumptions about vcpu_id<->apic_id relationship in hvmloader
Patch 5: Add logic to derive x2APIC IDs given a CPU policy and vCPU IDs
Patch 6: Includes a simple topology generator for toolstack so new guests
         have topologically consistent information in CPUID

Alejandro Vallejo (6):
  xen/x86: Add initial x2APIC ID to the per-vLAPIC save area
  tools/xc: Add xc_cpu_policy to the public xenctrl.h header
  xen/x86: Refactor xen/lib/x86 so it can be linked in hvmloader
  tools/hvmloader: Use cpu_policy to determine APIC IDs
  xen/x86: Derive topologically correct x2APIC IDs from the policy
  xen/x86: Add topology generator

 tools/firmware/hvmloader/Makefile        |   7 ++
 tools/firmware/hvmloader/config.h        |   5 +-
 tools/firmware/hvmloader/hvmloader.c     |   6 +
 tools/firmware/hvmloader/util.c          |   3 +-
 tools/include/xenguest.h                 |  23 +++-
 tools/libacpi/build.c                    |  27 ++++-
 tools/libacpi/libacpi.h                  |   5 +-
 tools/libs/guest/xg_cpuid_x86.c          | 144 ++++++++++++++---------
 tools/libs/guest/xg_private.h            |  10 --
 tools/libs/light/libxl_x86_acpi.c        |  21 +++-
 tools/tests/cpu-policy/test-cpu-policy.c | 128 ++++++++++++++++++++
 xen/arch/x86/cpu-policy.c                |   6 +-
 xen/arch/x86/cpuid.c                     |  20 +---
 xen/arch/x86/domain.c                    |   3 +
 xen/arch/x86/hvm/vlapic.c                |  27 ++++-
 xen/arch/x86/include/asm/hvm/vlapic.h    |   2 +
 xen/include/public/arch-x86/hvm/save.h   |   2 +
 xen/include/xen/lib/x86/cpu-policy.h     |  16 +++
 xen/lib/x86/cpuid.c                      |  12 +-
 xen/lib/x86/policy.c                     |  74 ++++++++++++
 xen/lib/x86/private.h                    |   8 +-
 21 files changed, 442 insertions(+), 107 deletions(-)