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[SPARC64]: Eliminate NR_CPUS limitations.

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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>
This commit is contained in:
David S. Miller 2007-05-26 01:14:43 -07:00
parent 5cbc307373
commit 22adb358e8
6 changed files with 43 additions and 16 deletions
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22
arch/sparc64/mm/init.c
View file

@ -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;