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authorDavid S. Miller <davem@sunset.davemloft.net>2007-05-26 01:14:43 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2007-05-29 02:49:49 -0700
commit22adb358e816ce6aa0afb231ae9d826b0bddc8b0 (patch)
tree6f9886bf5b4e5c916c72d8d5733211813873c5fc /arch/sparc64/mm
parent5cbc30737398b49f62ae8603129ce43ac7db1a41 (diff)
[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>
Diffstat (limited to 'arch/sparc64/mm')
-rw-r--r--arch/sparc64/mm/init.c22
1 files changed, 16 insertions, 6 deletions
diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c
index 977698269d3..087cbf09d0b 100644
--- a/arch/sparc64/mm/init.c
+++ b/arch/sparc64/mm/init.c
@@ -191,12 +191,9 @@ inline void flush_dcache_page_impl(struct page *page)
}
#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 @@ void __init paging_init(void)
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;