Re: [libvirt] [PATCH v3] qemu: Add check for whether KVM nesting is enabled

Support for nested KVM is handled via a kernel module configuration parameters values for kvm_intel, kvm_amd, kvm_hv (PPC), or kvm (s390). While it's possible to fetch the kmod config values via virKModConfig, unfortunately that is the static value and we need to get the current/dynamic value from the kernel file system. So this patch adds a new API virHostKVMSupportsNesting that will search the 3 kernel modules to get the nesting value and check if it is 'Y' (or 'y' just in case) or '1' to return a true/false whether the KVM kernel supports nesting. We need to do this in order to handle cases where adjustments to the value are made after libvirtd is started to force a refetch of the latest QEMU capabilities since the correct CPU settings need to be made for a guest to add the "vmx=on" to/for the guest config.