x86/resctrl: Handle number of RMIDs supported by RDT_RESOURCE_PERF_PKG

x86/resctrl: Handle number of RMIDs supported by RDT_RESOURCE_PERF_PKG

There are now three meanings for "number of RMIDs":

1) The number for legacy features enumerated by CPUID leaf 0xF. This is the
   maximum number of distinct values that can be loaded into MSR_IA32_PQR_ASSOC.
   Note that systems with Sub-NUMA Cluster mode enabled will force scaling down
   the CPUID enumerated value by the number of SNC nodes per L3-cache.

2) The number of registers in MMIO space for each event. This is enumerated in
   the XML files and is the value initialized into event_group::num_rmid.

3) The number of "hardware counters" (this isn't a strictly accurate
   description of how things work, but serves as a useful analogy that does
   describe the limitations) feeding to those MMIO registers. This is enumerated
   in telemetry_region::num_rmids returned by intel_pmt_get_regions_by_feature().

Event groups with insufficient "hardware counters" to track all RMIDs are
difficult for users to use, since the system may reassign "hardware counters"
at any time. This means that users cannot reliably collect two consecutive
event counts to compute the rate at which events are occurring.

Disable such event groups by default. The user may override this with
a command line "rdt=" option. In this case limit an under-resourced event
group's number of possible monitor resource groups to the lowest number of
"hardware counters".

Scan all enabled event groups and assign the RDT_RESOURCE_PERF_PKG resource
"num_rmid" value to the smallest of these values as this value will be used
later to compare against the number of RMIDs supported by other resources to
determine how many monitoring resource groups are supported.

N.B. Change type of resctrl_mon::num_rmid to u32 to match its usage and the
type of event_group::num_rmid so that min(r->num_rmid, e->num_rmid) won't
complain about mixing signed and unsigned types.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com