Re: [PATCH 05/10] KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC

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On 18/04/2024 20:34, David Woodhouse wrote:
From: David Woodhouse <dwmw@xxxxxxxxxxxx>

KVM does make an attempt to cope with non-constant TSC, and has notifiers
to handle host TSC frequency changes. However, it *only* adjusts the KVM
clock, and doesn't adjust TSC frequency scaling when the host changes.

This is presumably because non-constant TSCs were fixed in hardware long
before TSC scaling was implemented, so there should never be real CPUs
which have TSC scaling but *not* CONSTANT_TSC.

Such a combination could potentially happen in some odd L1 nesting
environment, but it isn't worth trying to support it. Just make the
dependency explicit.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
  arch/x86/kvm/svm/svm.c | 3 ++-
  arch/x86/kvm/vmx/vmx.c | 2 +-
  2 files changed, 3 insertions(+), 2 deletions(-)

Reviewed-by: Paul Durrant <paul@xxxxxxx>

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