[00/16] x86/tsc: Try to wrangle PV clocks vs. TSC

Message

Sean Christopherson Feb. 1, 2025, 2:17 a.m. UTC

Attempt to bring some amount of order to the PV clocks vs. TSC madness in
the kernel.  The primary goal of this series is to fix flaws with SNP
and TDX guests where a PV clock provided by the untrusted hypervisor is
used instead of the secure/trusted TSC that is controlled by trusted
firmware.

The secondary goal (last few patches) is to draft off of the SNP and TDX
changes to slightly modernize running under KVM.  Currently, KVM guests
will use TSC for clocksource, but not sched_clock.  And they ignore Intel's
CPUID-based TSC and CPU frequency enumeration, even when using the TSC
instead of kvmclock.  And if the host provides the core crystal frequency
in CPUID.0x15, then KVM guests can use that for the APIC timer period
instead of manually calibrating the frequency.

Lots more background: https://lore.kernel.org/all/[e-mail]

This is all *very* lightly tested (borderline RFC).

Sean Christopherson (16):
  x86/tsc: Add a standalone helpers for getting TSC info from CPUID.0x15
  x86/tsc: Add standalone helper for getting CPU frequency from CPUID
  x86/tsc: Add helper to register CPU and TSC freq calibration routines
  x86/sev: Mark TSC as reliable when configuring Secure TSC
  x86/sev: Move check for SNP Secure TSC support to tsc_early_init()
  x86/tdx: Override PV calibration routines with CPUID-based calibration
  x86/acrn: Mark TSC frequency as known when using ACRN for calibration
  x86/tsc: Pass KNOWN_FREQ and RELIABLE as params to registration
  x86/tsc: Rejects attempts to override TSC calibration with lesser
    routine
  x86/paravirt: Move handling of unstable PV clocks into
    paravirt_set_sched_clock()
  x86/paravirt: Don't use a PV sched_clock in CoCo guests with trusted
    TSC
  x86/kvmclock: Mark TSC as reliable when it's constant and nonstop
  x86/kvmclock: Get CPU base frequency from CPUID when it's available
  x86/kvmclock: Get TSC frequency from CPUID when its available
  x86/kvmclock: Stuff local APIC bus period when core crystal freq comes
    from CPUID
  x86/kvmclock: Use TSC for sched_clock if it's constant and non-stop

 arch/x86/coco/sev/core.c        |  9 ++--
 arch/x86/coco/tdx/tdx.c         | 27 ++++++++--
 arch/x86/include/asm/paravirt.h |  7 ++-
 arch/x86/include/asm/tdx.h      |  2 +
 arch/x86/include/asm/tsc.h      | 67 +++++++++++++++++++++++++
 arch/x86/kernel/cpu/acrn.c      |  5 +-
 arch/x86/kernel/cpu/mshyperv.c  | 11 +++--
 arch/x86/kernel/cpu/vmware.c    |  9 ++--
 arch/x86/kernel/jailhouse.c     |  6 +--
 arch/x86/kernel/kvmclock.c      | 88 +++++++++++++++++++++++----------
 arch/x86/kernel/paravirt.c      | 15 +++++-
 arch/x86/kernel/tsc.c           | 74 ++++++++++++++++-----------
 arch/x86/mm/mem_encrypt_amd.c   |  3 --
 arch/x86/xen/time.c             |  4 +-
 14 files changed, 243 insertions(+), 84 deletions(-)


base-commit: ebbb8be421eefbe2d47b99c2e1a6dd840d7930f9