[v8,0/9] i386: KVM: expand Hyper-V features early

Message

Vitaly Kuznetsov June 8, 2021, 12:08 p.m. UTC

Changes since v7:
- Make eVMCS version check future proof [Eduardo]
- Collect R-b tags [Eduardo]
- Drop 'if (!strcmp(arch, "i386") || !strcmp(arch, "x86_64"))' check from qtest
 [Eduardo]
- s/priviliges/privileges/ [Eric]

The last two functional patches are inspired by 'Fine-grained access check
to Hyper-V hypercalls and MSRs' work for KVM:
https://lore.kernel.org/kvm/[e-mail]/

Original description:

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).

Vitaly Kuznetsov (9):
  i386: avoid hardcoding '12' as 'hyperv_vendor_id' length
  i386: clarify 'hv-passthrough' behavior
  i386: hardcode supported eVMCS version to '1'
  i386: make hyperv_expand_features() return bool
  i386: expand Hyper-V features during CPU feature expansion time
  i386: kill off hv_cpuid_check_and_set()
  i386: HV_HYPERCALL_AVAILABLE privilege bit is always needed
  i386: Hyper-V SynIC requires POST_MESSAGES/SIGNAL_EVENTS privileges
  qtest/hyperv: Introduce a simple hyper-v test

 MAINTAINERS                    |   1 +
 docs/hyperv.txt                |   9 +-
 target/i386/cpu.c              |  13 +-
 target/i386/kvm/hyperv-proto.h |   6 +
 target/i386/kvm/kvm-stub.c     |   5 +
 target/i386/kvm/kvm.c          | 189 +++++++++++++++-------------
 target/i386/kvm/kvm_i386.h     |   1 +
 tests/qtest/hyperv-test.c      | 221 +++++++++++++++++++++++++++++++++
 tests/qtest/meson.build        |   3 +-
 9 files changed, 357 insertions(+), 91 deletions(-)
 create mode 100644 tests/qtest/hyperv-test.c

Comments

Eduardo Habkost July 7, 2021, 2 p.m. UTC | #1

On Tue, Jun 08, 2021 at 02:08:08PM +0200, Vitaly Kuznetsov wrote:
> Changes since v7:
> - Make eVMCS version check future proof [Eduardo]
> - Collect R-b tags [Eduardo]
> - Drop 'if (!strcmp(arch, "i386") || !strcmp(arch, "x86_64"))' check from qtest
>  [Eduardo]
> - s/priviliges/privileges/ [Eric]
> 
> The last two functional patches are inspired by 'Fine-grained access check
> to Hyper-V hypercalls and MSRs' work for KVM:
> https://lore.kernel.org/kvm/[e-mail]/
> 
> Original description:
> 
> 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).

I'm finally queueing this (please ignore my reply to v7).
Thanks, and sorry for the delay!