Re: [PATCH 0/3] KVM: x86: Fix KVM_FEATURE_PV_UNHALT update logic

[Sean Christopherson]

On Wed, 28 Feb 2024 11:18:34 +0100, Vitaly Kuznetsov wrote:
> Guest hangs in specific configurations (KVM_X86_DISABLE_EXITS_HLT) are
> reported and the issue was bisected to commit ee3a5f9e3d9b ("KVM: x86: Do
> runtime CPUID update before updating vcpu->arch.cpuid_entries") which, of
> course, carries "No functional change intended" blurb. Turns out, moving
> __kvm_update_cpuid_runtime() earlier in kvm_set_cpuid() to tweak the
> incoming CPUID data before checking it wasn't innocent as
> KVM_FEATURE_PV_UNHALT reset logic relies on cached KVM CPUID base which
> gets updated later.
> 
> [...]

Applied to kvm-x86 hyperv.  I won't send a pull request for this until next week,
but I do plan on landing it in 6.9.  Holler if the selftests tweaks look wrong
(or you just don't like them).  Thanks!

[1/3] KVM: x86: Introduce __kvm_get_hypervisor_cpuid() helper
      https://github.com/kvm-x86/linux/commit/92e82cf632e8
[2/3] KVM: x86: Use actual kvm_cpuid.base for clearing KVM_FEATURE_PV_UNHALT
      https://github.com/kvm-x86/linux/commit/4736d85f0d18
[3/3] KVM: selftests: Check that PV_UNHALT is cleared when HLT exiting is disabled
      https://github.com/kvm-x86/linux/commit/c2585047c8e1

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https://github.com/kvm-x86/linux/tree/next