Re: [PATCH v3 0/7] Add Security Guest doc and check for capabilities cache validation

This series introduces the concept of a 'Secure Guest' feature which covers on s390 IBM Secure Execution and on x86 AMD Secure Encrypted Virtualization. Besides adding documentation for IBM Secure Execution it also adds checks during validation of the qemu capabilities cache. These checks per architecture can be performed for IBM Secure Execution on s390 and AMD Secure Encrypted Virtualization on AMD x86 CPUs (both checks implemented in this series). For s390 the verification consists of: - checking if /sys/firmware/uv is available: meaning the HW facility is available and the host OS supports it; - checking if the kernel cmdline contains 'prot_virt=1': meaning the host OS wants to use the feature. For AMD Secure Encrypted Virtualization the verification consists of: - checking if /sys/module/kvm_amd/parameters/sev contains the value '1': meaning SEV is enabled in the host kernel; - checking if /dev/sev exists Whenever the availability of the feature does not match the secure guest flag in the cache then libvirt will re-build it in order to pick up the new set of capabilities available. Additionally, this series adds the same aforementioned checks to the virt-host-validate tool to facilitate the manual verification process for users.