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Commit 22adb358 authored by David S. Miller's avatar David S. Miller
Browse files

[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: default avatarDavid S. Miller <davem@davemloft.net>
parent 5cbc3073

arch/sparc64/Kconfig

+3 −3
Original line number Diff line number Diff line
@@ -147,10 +147,10 @@ config SMP 
	  If you don't know what to do here, say N.



config NR_CPUS

	int "Maximum number of CPUs (2-64)"

	range 2 64

	int "Maximum number of CPUs (2-1024)"

	range 2 1024

	depends on SMP

	default "32"

	default "64"



source "drivers/cpufreq/Kconfig"

arch/sparc64/kernel/head.S

+1 −1
Original line number Diff line number Diff line
@@ -523,7 +523,7 @@ tlb_fixup_done: 
#else

	mov	0, %o0

#endif

	stb	%o0, [%g6 + TI_CPU]

	sth	%o0, [%g6 + TI_CPU]



	/* Off we go.... */

	call	start_kernel

arch/sparc64/kernel/smp.c

+18 −1
Original line number Diff line number Diff line
@@ -400,7 +400,7 @@ static __inline__ void spitfire_xcall_deliver(u64 data0, u64 data1, u64 data2, c 
static void cheetah_xcall_deliver(u64 data0, u64 data1, u64 data2, cpumask_t mask)

{

	u64 pstate, ver;

	int nack_busy_id, is_jbus;

	int nack_busy_id, is_jbus, need_more;



	if (cpus_empty(mask))

		return;
@@ -416,6 +416,7 @@ static void cheetah_xcall_deliver(u64 data0, u64 data1, u64 data2, cpumask_t mas 
	__asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));



retry:

	need_more = 0;

	__asm__ __volatile__("wrpr %0, %1, %%pstate\n\t"

			     : : "r" (pstate), "i" (PSTATE_IE));
@@ -444,6 +445,10 @@ static void cheetah_xcall_deliver(u64 data0, u64 data1, u64 data2, cpumask_t mas 
				: /* no outputs */

				: "r" (target), "i" (ASI_INTR_W));

			nack_busy_id++;

			if (nack_busy_id == 32) {

				need_more = 1;

				break;

			}

		}

	}
@@ -460,6 +465,16 @@ static void cheetah_xcall_deliver(u64 data0, u64 data1, u64 data2, cpumask_t mas 
			if (dispatch_stat == 0UL) {

				__asm__ __volatile__("wrpr %0, 0x0, %%pstate"

						     : : "r" (pstate));

				if (unlikely(need_more)) {

					int i, cnt = 0;

					for_each_cpu_mask(i, mask) {

						cpu_clear(i, mask);

						cnt++;

						if (cnt == 32)

							break;

					}

					goto retry;

				}

				return;

			}

			if (!--stuck)
@@ -497,6 +512,8 @@ static void cheetah_xcall_deliver(u64 data0, u64 data1, u64 data2, cpumask_t mas 
				if ((dispatch_stat & check_mask) == 0)

					cpu_clear(i, mask);

				this_busy_nack += 2;

				if (this_busy_nack == 64)

					break;

			}



			goto retry;

arch/sparc64/mm/init.c

+16 −6
Original line number Diff line number Diff line
@@ -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;

include/asm-sparc64/cpudata.h

+1 −1
Original line number Diff line number Diff line
@@ -202,7 +202,7 @@ extern struct sun4v_2insn_patch_entry __sun4v_2insn_patch, 
 * the calculations done by the macro mid-stream.

 */

#define LOAD_PER_CPU_BASE(DEST, THR, REG1, REG2, REG3)	\

	ldub	[THR + TI_CPU], REG1;			\

	lduh	[THR + TI_CPU], REG1;			\

	sethi	%hi(__per_cpu_shift), REG3;		\

	sethi	%hi(__per_cpu_base), REG2;		\

	ldx	[REG3 + %lo(__per_cpu_shift)], REG3;	\