x86/intel_rdt: Show bitmask of shareable resource with other executing units

CPUID.(EAX=0x10, ECX=res#):EBX[31:0] reports a bit mask for a resource.
Each set bit within the length of the CBM indicates the corresponding
unit of the resource allocation may be used by other entities in the
platform (e.g. an integrated graphics engine or hardware units outside
the processor core and have direct access to the resource). Each
cleared bit within the length of the CBM indicates the corresponding
allocation unit can be configured to implement a priority-based
allocation scheme without interference with other hardware agents in
the system. Bits outside the length of the CBM are reserved.

More details on the bit mask are described in x86 Software Developer's
Manual.

The bitmask is shown in "info" directory for each resource. It's
up to user to decide how to use the bitmask within a CBM in a partition
to share or isolate a resource with other executing units.

Suggested-by: Reinette Chatre <[e-mail]>
Signed-off-by: Fenghua Yu <[e-mail]>
Signed-off-by: Tony Luck <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]

Documentation/x86/intel_rdt_ui.txt

···
 "min_cbm_bits": 	The minimum number of consecutive bits which
 			must be set when writing a mask.
 
+"shareable_bits":	Bitmask of shareable resource with other executing
+			entities (e.g. I/O). User can use this when
+			setting up exclusive cache partitions. Note that
+			some platforms support devices that have their
+			own settings for cache use which can over-ride
+			these bits.
+
 Memory bandwitdh(MB) subdirectory contains the following files
 with respect to allocation:
 

arch/x86/kernel/cpu/intel_rdt.c

···
 		r->num_closid = 4;
 		r->default_ctrl = max_cbm;
 		r->cache.cbm_len = 20;
+		r->cache.shareable_bits = 0xc0000;
 		r->cache.min_cbm_bits = 2;
 		r->alloc_capable = true;
 		r->alloc_enabled = true;
···
 	r->num_closid = edx.split.cos_max + 1;
 	r->cache.cbm_len = eax.split.cbm_len + 1;
 	r->default_ctrl = BIT_MASK(eax.split.cbm_len + 1) - 1;
+	r->cache.shareable_bits = ebx & r->default_ctrl;
 	r->data_width = (r->cache.cbm_len + 3) / 4;
 	r->alloc_capable = true;
 	r->alloc_enabled = true;

arch/x86/kernel/cpu/intel_rdt.h

···
  * @cbm_idx_offset:	Offset of CBM index. CBM index is computed by:
  *			closid * cbm_idx_multi + cbm_idx_offset
  *			in a cache bit mask
+ * @shareable_bits:	Bitmask of shareable resource with other
+ *			executing entities
  */
 struct rdt_cache {
 	unsigned int	cbm_len;
 	unsigned int	min_cbm_bits;
 	unsigned int	cbm_idx_mult;
 	unsigned int	cbm_idx_offset;
+	unsigned int	shareable_bits;
 };
 
 /**

arch/x86/kernel/cpu/intel_rdt_rdtgroup.c

···
 	return 0;
 }
 
+static int rdt_shareable_bits_show(struct kernfs_open_file *of,
+				   struct seq_file *seq, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+
+	seq_printf(seq, "%x\n", r->cache.shareable_bits);
+	return 0;
+}
+
 static int rdt_min_bw_show(struct kernfs_open_file *of,
 			     struct seq_file *seq, void *v)
 {
···
 		.mode		= 0444,
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= rdt_min_cbm_bits_show,
+		.fflags		= RF_CTRL_INFO | RFTYPE_RES_CACHE,
+	},
+	{
+		.name		= "shareable_bits",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdt_shareable_bits_show,
 		.fflags		= RF_CTRL_INFO | RFTYPE_RES_CACHE,
 	},
 	{