[PATCH RFC 00/22] KVM: x86: hyper-v: Fine-grained access check to Hyper-V hypercalls and MSRs

[Vitaly Kuznetsov]

Currently, all implemented Hyper-V features (MSRs and hypercalls) are
available unconditionally to all Hyper-V enabled guests. This is not
ideal as KVM userspace may decide to provide only a subset of the
currently implemented features to emulate an older Hyper-V version,
to reduce attack surface,... Implement checks against guest visible
CPUIDs for all currently implemented MSRs and hypercalls.

RFC part:
- KVM has KVM_CAP_ENFORCE_PV_FEATURE_CPUID for KVM PV features. Should
 we use it for Hyper-V as well or should we rather add a Hyper-V specific
 CAP (or neither)?

TODO:
- Write a selftest
- Check with various Windows/Hyper-V versions that CPUID feature bits
 are actually respected.

Vitaly Kuznetsov (22):
  asm-generic/hyperv: add HV_STATUS_ACCESS_DENIED definition
  KVM: x86: hyper-v: Cache guest CPUID leaves determining features
    availability
  KVM: x86: hyper-v: Honor HV_MSR_VP_RUNTIME_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_TIME_REF_COUNT_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_HYPERCALL_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_VP_INDEX_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_RESET_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_REFERENCE_TSC_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_SYNIC_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_SYNTIMER_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_MSR_APIC_ACCESS_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_ACCESS_FREQUENCY_MSRS privilege bit
  KVM: x86: hyper-v: Honor HV_ACCESS_REENLIGHTENMENT privilege bit
  KVM: x86: hyper-v: Honor HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE
    privilege bit
  KVM: x86: hyper-v: Honor HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE
    privilege bit
  KVM: x86: hyper-v: Honor HV_STIMER_DIRECT_MODE_AVAILABLE privilege bit
  KVM: x86: hyper-v: Honor HV_POST_MESSAGES privilege bit
  KVM: x86: hyper-v: Honor HV_SIGNAL_EVENTS privilege bit
  KVM: x86: hyper-v: Honor HV_DEBUGGING privilege bit
  KVM: x86: hyper-v: Honor HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED bit
  KVM: x86: hyper-v: Honor HV_X64_CLUSTER_IPI_RECOMMENDED bit
  KVM: x86: hyper-v: Check access to HVCALL_NOTIFY_LONG_SPIN_WAIT
    hypercall

 arch/x86/include/asm/kvm_host.h   |   8 +
 arch/x86/kvm/hyperv.c             | 305 +++++++++++++++++++++++++++---
 include/asm-generic/hyperv-tlfs.h |   1 +
 3 files changed, 291 insertions(+), 23 deletions(-)

-- 
2.30.2