x86/sysctl: Implement XEN_SYSCTL_get_cpu_policy

x86/sysctl: Implement XEN_SYSCTL_get_cpu_policy

Provide a SYSCTL for the toolstack to obtain complete system CPUID and MSR
policy information.

For the flask side of things, this subop is closely related to
{phys,cputopo,numa}info, so shares the physinfo access vector.

Extend the xen-cpuid utility to be able to dump the system policies.  An
example output is:

  Xen reports there are maximum 113 leaves and 3 MSRs
  Raw policy: 93 leaves, 3 MSRs
   CPUID:
    leaf     subleaf  -> eax      ebx      ecx      edx
    00000000:ffffffff -> 0000000d:756e6547:6c65746e:49656e69
    00000001:ffffffff -> 000306c3:00100800:7ffafbff:bfebfbff
    00000002:ffffffff -> 76036301:00f0b5ff:00000000:00c10000
    00000004:00000000 -> 1c004121:01c0003f:0000003f:00000000
    00000004:00000001 -> 1c004122:01c0003f:0000003f:00000000
    00000004:00000002 -> 1c004143:01c0003f:000001ff:00000000
    00000004:00000003 -> 1c03c163:03c0003f:00001fff:00000006
    00000005:ffffffff -> 00000040:00000040:00000003:00042120
    00000006:ffffffff -> 00000077:00000002:00000009:00000000
    00000007:00000000 -> 00000000:000027ab:00000000:9c000000
    0000000a:ffffffff -> 07300403:00000000:00000000:00000603
    0000000b:00000000 -> 00000001:00000002:00000100:00000000
    0000000b:00000001 -> 00000004:00000008:00000201:00000000
    0000000d:00000000 -> 00000007:00000340:00000340:00000000
    0000000d:00000001 -> 00000001:00000000:00000000:00000000
    0000000d:00000002 -> 00000100:00000240:00000000:00000000
    80000000:ffffffff -> 80000008:00000000:00000000:00000000
    80000001:ffffffff -> 00000000:00000000:00000021:2c100800
    80000002:ffffffff -> 65746e49:2952286c:6f655820:2952286e
    80000003:ffffffff -> 55504320:2d334520:30343231:20337620
    80000004:ffffffff -> 2e332040:48473034:0000007a:00000000
    80000006:ffffffff -> 00000000:00000000:01006040:00000000
    80000007:ffffffff -> 00000000:00000000:00000000:00000100
    80000008:ffffffff -> 00003027:00000000:00000000:00000000
   MSRs:
    index    -> value
    000000ce -> 0000000080000000

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Wei Liu <wei.liu2@citrix.com>