[PATCH v2 0/7] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful

[Vitaly Kuznetsov]

Changes since v1:
- Rebased to kvm/queue [KVM_CAP_SYS_HYPERV_CPUID -> 188]

QEMU series using the feature:
https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg02017.html

Original description:

KVM_GET_SUPPORTED_HV_CPUID was initially implemented as a vCPU ioctl but
this is not very useful when VMM is just trying to query which Hyper-V
features are supported by the host prior to creating VM/vCPUs. The data
in KVM_GET_SUPPORTED_HV_CPUID is mostly static with a few exceptions but
it seems we can change this. Add support for KVM_GET_SUPPORTED_HV_CPUID as
a system ioctl as well.

QEMU specific description:
In some cases QEMU needs to collect the information about which Hyper-V
features are supported by KVM and pass it up the stack. For non-hyper-v
features this is done with system-wide KVM_GET_SUPPORTED_CPUID/
KVM_GET_MSRS ioctls but Hyper-V specific features don't get in the output
(as Hyper-V CPUIDs intersect with KVM's). In QEMU, CPU feature expansion
happens before any KVM vcpus are created so KVM_GET_SUPPORTED_HV_CPUID
can't be used in its current shape.

Vitaly Kuznetsov (7):
  KVM: x86: hyper-v: Mention SynDBG CPUID leaves in api.rst
  KVM: x86: hyper-v: disallow configuring SynIC timers with no SynIC
  KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID output independent
    of eVMCS enablement
  KVM: x86: hyper-v: always advertise HV_STIMER_DIRECT_MODE_AVAILABLE
  KVM: x86: hyper-v: drop now unneeded vcpu parameter from
    kvm_vcpu_ioctl_get_hv_cpuid()
  KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID as a system ioctl
  KVM: selftests: test KVM_GET_SUPPORTED_HV_CPUID as a system ioctl

 Documentation/virt/kvm/api.rst                | 12 +--
 arch/x86/include/asm/kvm_host.h               |  2 +-
 arch/x86/kvm/hyperv.c                         | 30 ++++----
 arch/x86/kvm/hyperv.h                         |  3 +-
 arch/x86/kvm/vmx/evmcs.c                      |  8 +-
 arch/x86/kvm/vmx/evmcs.h                      |  2 +-
 arch/x86/kvm/x86.c                            | 44 ++++++-----
 include/uapi/linux/kvm.h                      |  3 +-
 .../testing/selftests/kvm/include/kvm_util.h  |  2 +
 tools/testing/selftests/kvm/lib/kvm_util.c    | 26 +++++++
 .../selftests/kvm/x86_64/hyperv_cpuid.c       | 77 +++++++++----------
 11 files changed, 120 insertions(+), 89 deletions(-)

-- 
2.25.4