x86/platform/UV: Add kernel parameter to set memory block size

Add a kernel parameter that allows setting UV memory block size.  This
is to provide an adjustment for new forms of PMEM and other DIMM memory
that might require alignment restrictions other than scanning the global
address table for the required minimum alignment.  The value set will be
further adjusted by both the GAM range table scan as well as restrictions
imposed by set_memory_block_size_order().

Signed-off-by: Mike Travis <mike.travis@hpe.com>
Reviewed-by: Andrew Banman <andrew.banman@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <russ.anderson@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Cc: jgross@suse.com
Cc: kirill.shutemov@linux.intel.com
Cc: mhocko@suse.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/lkml/20180524201711.854849120@stormcage.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -396,6 +396,17 @@ EXPORT_SYMBOL(uv_hub_info_version);
 /* Default UV memory block size is 2GB */
 static unsigned long mem_block_size = (2UL << 30);
 
+/* Kernel parameter to specify UV mem block size */
+static int parse_mem_block_size(char *ptr)
+{
+	unsigned long size = memparse(ptr, NULL);
+
+	/* Size will be rounded down by set_block_size() below */
+	mem_block_size = size;
+	return 0;
+}
+early_param("uv_memblksize", parse_mem_block_size);
+
 static __init int adj_blksize(u32 lgre)
 {
 	unsigned long base = (unsigned long)lgre << UV_GAM_RANGE_SHFT;