Always use safe MSR accesses in PV guests

configname: CONFIG_XEN_PV_MSR_SAFE

Linux Kernel Configuration
└─>Processor type and features
└─>Linux guest support
└─>Always use safe MSR accesses in PV guests
In linux kernel since version 6.1 (release Date: 2022-12-11)
Use safe (not faulting) MSR access functions even if the MSR access
should not fault anyway.
The default can be changed by using the "xen_msr_safe" boot parameter.