[SPARC64]: Document the instruction checks we do in do_sparc64_fault().

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc64/mm/fault.c b/arch/sparc64/mm/fault.c
index 0db2f7d9fab50ff57ff5d7125ed731afdbf5f445..6e002aacb961832113ba30d522d437460ee20612 100644 (file)
--- a/arch/sparc64/mm/fault.c
+++ b/arch/sparc64/mm/fault.c
@@ -327,8 +327,12 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
                insn = get_fault_insn(regs, 0);
                if (!insn)
                        goto continue_fault;
+               /* All loads, stores and atomics have bits 30 and 31 both set
+                * in the instruction.  Bit 21 is set in all stores, but we
+                * have to avoid prefetches which also have bit 21 set.
+                */
                if ((insn & 0xc0200000) == 0xc0200000 &&
-                   (insn & 0x1780000) != 0x1680000) {
+                   (insn & 0x01780000) != 0x01680000) {
                        /* Don't bother updating thread struct value,
                         * because update_mmu_cache only cares which tlb
                         * the access came from.