[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>

4 files changed, 38 insertions, 11 deletions

diff --git a/arch/sparc64/Kconfig b/arch/sparc64/Kconfig
index 831781cab271..bd00f89eed1e 100644
--- a/arch/sparc64/Kconfig
+++ b/arch/sparc64/Kconfig
@@ -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"
 
diff --git a/arch/sparc64/kernel/head.S b/arch/sparc64/kernel/head.S
index baea10a98196..5c11529742d4 100644
--- a/arch/sparc64/kernel/head.S
+++ b/arch/sparc64/kernel/head.S
@@ -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
diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
index f7fa873c800d..c550bba3490a 100644
--- a/arch/sparc64/kernel/smp.c
+++ b/arch/sparc64/kernel/smp.c
@@ -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 @@ retry:
                                 : /* no outputs */
                                 : "r" (target), "i" (ASI_INTR_W));
                         nack_busy_id++;
+                        if (nack_busy_id == 32) {
+                                need_more = 1;
+                                break;
+                        }
                 }
         }
 
@@ -460,6 +465,16 @@ retry:
                         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 @@ retry:
                                 if ((dispatch_stat & check_mask) == 0)
                                         cpu_clear(i, mask);
                                 this_busy_nack += 2;
+                                if (this_busy_nack == 64)
+                                        break;
                         }
 
                         goto retry;
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;