[PATCH RFC v3 00/23] i386: KVM: expand Hyper-V features early

[Vitaly Kuznetsov]

Another week another RFC. KVM patches are still in flight, so RFC again.

Changes since RFCv2:
- Rebase.
- Split "i386: drop FEAT_HYPERV feature leaves" into several patches and
  re-shuffle patches to minimize the code churn and make it easier to
  review. [Eduardo]
- Added "i386: provide simple 'hyperv=on' option to x86 machine types" on
  top.

This pairs with
https://lore.kernel.org/kvm/20200929150944.1235688-1-vkuznets@redhat.com/T/#t

Upper layer tools like libvirt want to figure out which Hyper-V features are
supported by the underlying stack (QEMU/KVM) but currently they are unable to
do so. We have a nice 'hv_passthrough' CPU flag supported by QEMU but it has
no effect on e.g. QMP's 

query-cpu-model-expansion type=full 
model={"name":"host","props":{"hv-passthrough":true}}

command as we parse Hyper-V features after creating KVM vCPUs and not at
feature expansion time. To support the use-case we first need to make 
KVM_GET_SUPPORTED_HV_CPUID ioctl a system-wide ioctl as the existing
vCPU version can't be used that early. This is what KVM part does. With
that done, we can make early Hyper-V feature expansion (this series).

In addition, add a simple 'hyperv=on' option to x86 machine types which
enables (and requires from KVM) all currently supported Hyper-V enlightenments.
Unlike 'hv_passthrough' mode, this is going to be migratable.

Vitaly Kuznetsov (23):
  WIP: update linux/headers
  i386: fill in FEAT_HYPERV_EDX from edx instead of eax
  i386: drop x86_cpu_get_supported_feature_word() forward declaration
  i386: move hyperv_vendor_id initialization to x86_cpu_realizefn()
  i386: move hyperv_interface_id initialization to x86_cpu_realizefn()
  i386: move hyperv_version_id initialization to x86_cpu_realizefn()
  i386: move hyperv_limits initialization to x86_cpu_realizefn()
  i386: keep hyperv_vendor string up-to-date
  i386: invert hyperv_spinlock_attempts setting logic with
    hv_passthrough
  i386: always fill Hyper-V CPUID feature leaves from X86CPU data
  i386: stop using env->features[] for filling Hyper-V CPUIDs
  i386: introduce hyperv_feature_supported()
  i386: introduce hv_cpuid_get_host()
  i386: drop FEAT_HYPERV feature leaves
  i386: introduce hv_cpuid_cache
  i386: split hyperv_handle_properties() into
    hyperv_expand_features()/hyperv_fill_cpuids()
  i386: move eVMCS enablement to hyperv_init_vcpu()
  i386: switch hyperv_expand_features() to using error_setg()
  i386: adjust the expected KVM_GET_SUPPORTED_HV_CPUID array size
  i386: prefer system KVM_GET_SUPPORTED_HV_CPUID ioctl over vCPU's one
  i386: use global kvm_state in hyperv_enabled() check
  i386: expand Hyper-V features during CPU feature expansion time
  i386: provide simple 'hyperv=on' option to x86 machine types

 docs/hyperv.txt             |   8 +
 hw/i386/x86.c               |  30 ++
 include/hw/i386/x86.h       |   7 +
 linux-headers/asm-x86/kvm.h |  20 ++
 linux-headers/linux/kvm.h   |  27 +-
 target/i386/cpu.c           | 149 ++++------
 target/i386/cpu.h           |  12 +-
 target/i386/kvm-stub.c      |   5 +
 target/i386/kvm.c           | 526 ++++++++++++++++++++----------------
 target/i386/kvm_i386.h      |   1 +
 10 files changed, 457 insertions(+), 328 deletions(-)

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2.25.4