powerpc/e6500: TLB miss handler with hardware tablewalk support

There are a few things that make the existing hw tablewalk handlers
unsuitable for e6500:

 - Indirect entries go in TLB1 (though the resulting direct entries go in
   TLB0).

 - It has threads, but no "tlbsrx." -- so we need a spinlock and
   a normal "tlbsx".  Because we need this lock, hardware tablewalk
   is mandatory on e6500 unless we want to add spinlock+tlbsx to
   the normal bolted TLB miss handler.

 - TLB1 has no HES (nor next-victim hint) so we need software round robin
   (TODO: integrate this round robin data with hugetlb/KVM)

 - The existing tablewalk handlers map half of a page table at a time,
   because IBM hardware has a fixed 1MiB indirect page size.  e6500
   has variable size indirect entries, with a minimum of 2MiB.
   So we can't do the half-page indirect mapping, and even if we
   could it would be less efficient than mapping the full page.

 - Like on e5500, the linear mapping is bolted, so we don't need the
   overhead of supporting nested tlb misses.

Note that hardware tablewalk does not work in rev1 of e6500.
We do not expect to support e6500 rev1 in mainline Linux.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 2232aff66059..1ce9b87d7df8 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -97,6 +97,36 @@ int dcache_bsize;
 int icache_bsize;
 int ucache_bsize;
 
+#if defined(CONFIG_PPC_BOOK3E) && defined(CONFIG_SMP)
+static void setup_tlb_core_data(void)
+{
+        int cpu;
+
+        for_each_possible_cpu(cpu) {
+                int first = cpu_first_thread_sibling(cpu);
+
+                paca[cpu].tcd_ptr = &paca[first].tcd;
+
+                /*
+                 * If we have threads, we need either tlbsrx.
+                 * or e6500 tablewalk mode, or else TLB handlers
+                 * will be racy and could produce duplicate entries.
+                 */
+                if (smt_enabled_at_boot >= 2 &&
+                    !mmu_has_feature(MMU_FTR_USE_TLBRSRV) &&
+                    book3e_htw_mode != PPC_HTW_E6500) {
+                        /* Should we panic instead? */
+                        WARN_ONCE("%s: unsupported MMU configuration -- expect problems\n",
+                                  __func__);
+                }
+        }
+}
+#else
+static void setup_tlb_core_data(void)
+{
+}
+#endif
+
 #ifdef CONFIG_SMP
 
 static char *smt_enabled_cmdline;
@@ -445,6 +475,7 @@ void __init setup_system(void)
 
         smp_setup_cpu_maps();
         check_smt_enabled();
+        setup_tlb_core_data();
 
 #ifdef CONFIG_SMP
         /* Release secondary cpus out of their spinloops at 0x60 now that