I don’t know enough about Xen to be sure, but I know typically your dom0 is a Linux kernel even (or especially) with HVM. If it’s been patched and is performing

I don’t know enough about Xen to be sure, but I know typically your dom0 is a Linux kernel even (or especially) with HVM. If it’s been patched and is performing any paging on behalf of the guest, this will indeed affect performance of both paravirt and HVM instances.