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Subject[PATCH v3 0/2] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful
Date
Changes since v2:
- Keep vCPU version of the ioctl intact but make it 'deprecated' in
api.rst [Paolo Bonzini]
- First two patches of v2 series already made it to kvm/queue

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 (2):
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 | 16 ++--
arch/x86/kvm/hyperv.c | 6 +-
arch/x86/kvm/hyperv.h | 4 +-
arch/x86/kvm/vmx/evmcs.c | 3 +-
arch/x86/kvm/x86.c | 45 ++++++----
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 | 87 +++++++++++--------
9 files changed, 123 insertions(+), 69 deletions(-)

--
2.25.4

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