[SPARC64]: Eliminate NR_CPUS limitations.
Cheetah systems can have cpuids as large as 1023, although physical
systems don't have that many cpus.
Only three limitations existed in the kernel preventing arbitrary
NR_CPUS values:
1) dcache dirty cpu state stored in page->flags on
D-cache aliasing platforms. With some build time
calculations and some build-time BUG checks on
page->flags layout, this one was easily solved.
2) The cheetah XCALL delivery code could only handle
a cpumask with up to 32 cpus set. Some simple looping
logic clears that up too.
3) thread_info->cpu was a u8, easily changed to a u16.
There are a few spots in the kernel that still put NR_CPUS
sized arrays on the kernel stack, but that's not a sparc64
specific problem.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c
index 9776982..087cbf0 100644
--- a/arch/sparc64/mm/init.c
+++ b/arch/sparc64/mm/init.c
@@ -191,12 +191,9 @@
}
#define PG_dcache_dirty PG_arch_1
-#define PG_dcache_cpu_shift 24UL
-#define PG_dcache_cpu_mask (256UL - 1UL)
-
-#if NR_CPUS > 256
-#error D-cache dirty tracking and thread_info->cpu need fixing for > 256 cpus
-#endif
+#define PG_dcache_cpu_shift 32UL
+#define PG_dcache_cpu_mask \
+ ((1UL<<ilog2(roundup_pow_of_two(NR_CPUS)))-1UL)
#define dcache_dirty_cpu(page) \
(((page)->flags >> PG_dcache_cpu_shift) & PG_dcache_cpu_mask)
@@ -1349,6 +1346,19 @@
unsigned long end_pfn, pages_avail, shift, phys_base;
unsigned long real_end, i;
+ /* These build time checkes make sure that the dcache_dirty_cpu()
+ * page->flags usage will work.
+ *
+ * When a page gets marked as dcache-dirty, we store the
+ * cpu number starting at bit 32 in the page->flags. Also,
+ * functions like clear_dcache_dirty_cpu use the cpu mask
+ * in 13-bit signed-immediate instruction fields.
+ */
+ BUILD_BUG_ON(FLAGS_RESERVED != 32);
+ BUILD_BUG_ON(SECTIONS_WIDTH + NODES_WIDTH + ZONES_WIDTH +
+ ilog2(roundup_pow_of_two(NR_CPUS)) > FLAGS_RESERVED);
+ BUILD_BUG_ON(NR_CPUS > 4096);
+
kern_base = (prom_boot_mapping_phys_low >> 22UL) << 22UL;
kern_size = (unsigned long)&_end - (unsigned long)KERNBASE;