x86/resctrl: Add a new field to struct rmid_read for summation of domains

When a user reads a monitor file rdtgroup_mondata_show() calls mon_event_read()
to package up all the required details into an rmid_read structure which is
passed across the smp_call*() infrastructure to code that will read data from
hardware and return the value (or error status) in the rmid_read structure.

Sub-NUMA Cluster (SNC) mode adds files with new semantics. These require the
smp_call-ed code to sum event data from all domains that share an L3 cache.

Add a pointer to the L3 "cacheinfo" structure to struct rmid_read for the data
collection routines to use to pick the domains to be summed.

  [ Reinette: the rmid_read structure has become complex enough so document each
    of its fields and provide the kerneldoc documentation for struct rmid_read. ]
Co-developed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20240628215619.76401-10-tony.luck@intel.com

arch/x86/kernel/cpu/resctrl/internal.h

@@ -144,12 +144,31 @@ union mon_data_bits {
 	} u;
 };
 
+/**
+ * struct rmid_read - Data passed across smp_call*() to read event count.
+ * @rgrp:  Resource group for which the counter is being read. If it is a parent
+ *	   resource group then its event count is summed with the count from all
+ *	   its child resource groups.
+ * @r:	   Resource describing the properties of the event being read.
+ * @d:	   Domain that the counter should be read from. If NULL then sum all
+ *	   domains in @r sharing L3 @ci.id
+ * @evtid: Which monitor event to read.
+ * @first: Initialize MBM counter when true.
+ * @ci:    Cacheinfo for L3. Only set when @d is NULL. Used when summing domains.
+ * @err:   Error encountered when reading counter.
+ * @val:   Returned value of event counter. If @rgrp is a parent resource group,
+ *	   @val includes the sum of event counts from its child resource groups.
+ *	   If @d is NULL, @val includes the sum of all domains in @r sharing @ci.id,
+ *	   (summed across child resource groups if @rgrp is a parent resource group).
+ * @arch_mon_ctx: Hardware monitor allocated for this read request (MPAM only).
+ */
 struct rmid_read {
 	struct rdtgroup		*rgrp;
 	struct rdt_resource	*r;
 	struct rdt_mon_domain	*d;
 	enum resctrl_event_id	evtid;
 	bool			first;
+	struct cacheinfo	*ci;
 	int			err;
 	u64			val;
 	void			*arch_mon_ctx;