x86/platform/UV: Add adjustable set memory block size function

Add a new function to "adjust" the current fixed UV memory block size
of 2GB so it can be changed to a different physical boundary.  This is
out of necessity so arch dependent code can accommodate specific BIOS
requirements which can align these new PMEM modules at less than the
default boundaries.

A "set order" type of function was used to insure that the memory block
size will be a power of two value without requiring a validity check.
64GB was chosen as the upper limit for memory block size values to
accommodate upcoming 4PB systems which have 6 more bits of physical
address space (46 becoming 52).

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/20180524201711.609546602@stormcage.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 17 insertions, 4 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0a400606dea0..20d8bf5fbceb 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1350,16 +1350,28 @@ int kern_addr_valid(unsigned long addr)
 /* Amount of ram needed to start using large blocks */
 #define MEM_SIZE_FOR_LARGE_BLOCK (64UL << 30)
 
+/* Adjustable memory block size */
+static unsigned long set_memory_block_size;
+int __init set_memory_block_size_order(unsigned int order)
+{
+        unsigned long size = 1UL << order;
+
+        if (size > MEM_SIZE_FOR_LARGE_BLOCK || size < MIN_MEMORY_BLOCK_SIZE)
+                return -EINVAL;
+
+        set_memory_block_size = size;
+        return 0;
+}
+
 static unsigned long probe_memory_block_size(void)
 {
         unsigned long boot_mem_end = max_pfn << PAGE_SHIFT;
         unsigned long bz;
 
-        /* If this is UV system, always set 2G block size */
-        if (is_uv_system()) {
-                bz = MAX_BLOCK_SIZE;
+        /* If memory block size has been set, then use it */
+        bz = set_memory_block_size;
+        if (bz)
                 goto done;
-        }
 
         /* Use regular block if RAM is smaller than MEM_SIZE_FOR_LARGE_BLOCK */
         if (boot_mem_end < MEM_SIZE_FOR_LARGE_BLOCK) {
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 31ca3e28b0eb..a6ddefc60517 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -38,6 +38,7 @@ struct memory_block {
 
 int arch_get_memory_phys_device(unsigned long start_pfn);
 unsigned long memory_block_size_bytes(void);
+int set_memory_block_size_order(unsigned int order);
 
 /* These states are exposed to userspace as text strings in sysfs */
 #define MEM_ONLINE              (1<<0) /* exposed to userspace */