[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>

1 files changed, 18 insertions, 1 deletions

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;