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| author | David S. Miller <davem@sunset.davemloft.net> | 2007-05-26 01:14:43 -0700 |
|---|---|---|
| committer | David S. Miller <davem@sunset.davemloft.net> | 2007-05-29 02:49:49 -0700 |
| commit | 22adb358e816ce6aa0afb231ae9d826b0bddc8b0 (patch) | |
| tree | 6f9886bf5b4e5c916c72d8d5733211813873c5fc /arch/sparc64/mm | |
| parent | 5cbc30737398b49f62ae8603129ce43ac7db1a41 (diff) | |
| download | linux-22adb358e816ce6aa0afb231ae9d826b0bddc8b0.tar.bz2 | |
[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.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c index 977698269d3a..087cbf09d0b7 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; |