KVM advertises ARCH_CAPABILITIES regardless of hardware support
Issue
The CPUID flag ARCH_CAPABILITIES is unconditionally exposed to host userspace for all x86 hosts, i.e. KVM advertises ARCH_CAPABILITIES regardless of hardware support under the pretense that KVM fully emulates MSR_IA32_ARCH_CAPABILITIES. Unfortunately, only VMX hosts handle accesses to MSR_IA32_ARCH_CAPABILITIES (despite KVM_GET_MSRS also reporting MSR_IA32_ARCH_CAPABILITIES for all hosts).
This can result in guests not booting due to kernel panics.
Environment
Red Hat Linux 7
Red Hat Openstack Platform 10
qemu-kvm-rhev 2.12.0-33.el7_7.7
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