[SPARC64]: Get SUN4V SMP working.

The sibling cpu bringup is extremely fragile.  We can only
perform the most basic calls until we take over the trap
table from the firmware/hypervisor on the new cpu.

This means no accesses to %g4, %g5, %g6 since those can't be
TLB translated without our trap handlers.

In order to achieve this:

1) Change sun4v_init_mondo_queues() so that it can operate in
   several modes.

   It can allocate the queues, or install them in the current
   processor, or both.

   The boot cpu does both in it's call early on.

   Later, the boot cpu allocates the sibling cpu queue, starts
   the sibling cpu, then the sibling cpu loads them in.

2) init_cur_cpu_trap() is changed to take the current_thread_info()
   as an argument instead of reading %g6 directly on the current
   cpu.

3) Create a trampoline stack for the sibling cpus.  We do our basic
   kernel calls using this stack, which is locked into the kernel
   image, then go to our proper thread stack after taking over the
   trap table.

4) While we are in this delicate startup state, we put 0xdeadbeef
   into %g4/%g5/%g6 in order to catch accidental accesses.

5) On the final prom_set_trap_table*() call, we put &init_thread_union
   into %g6.  This is a hack to make prom_world(0) work.  All that
   wants to do is restore the %asi register using
   get_thread_current_ds().

Longer term we should just do the OBP calls to set the trap table by
hand just like we do for everything else.  This would avoid that silly
prom_world(0) issue, then we can remove the init_thread_union hack.

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

1 files changed, 56 insertions, 36 deletions

diff --git a/arch/sparc64/kernel/trampoline.S b/arch/sparc64/kernel/trampoline.S
index b9c9f54b0a00..a4dc01a3d238 100644
--- a/arch/sparc64/kernel/trampoline.S
+++ b/arch/sparc64/kernel/trampoline.S
@@ -30,12 +30,16 @@ itlb_load:
 dtlb_load:
         .asciz  "SUNW,dtlb-load"
 
+        /* XXX __cpuinit this thing XXX */
+#define TRAMP_STACK_SIZE        1024
+        .align  16
+tramp_stack:
+        .skip   TRAMP_STACK_SIZE
+
         .text
         .align          8
         .globl          sparc64_cpu_startup, sparc64_cpu_startup_end
 sparc64_cpu_startup:
-        flushw
-
         BRANCH_IF_SUN4V(g1, niagara_startup)
         BRANCH_IF_CHEETAH_BASE(g1, g5, cheetah_startup)
         BRANCH_IF_CHEETAH_PLUS_OR_FOLLOWON(g1, g5, cheetah_plus_startup)
@@ -58,6 +62,7 @@ cheetah_startup:
         or      %g5, DCU_DM | DCU_IM | DCU_DC | DCU_IC, %g5
         stxa    %g5, [%g0] ASI_DCU_CONTROL_REG
         membar  #Sync
+        /* fallthru */
 
 cheetah_generic_startup:
         mov     TSB_EXTENSION_P, %g3
@@ -90,19 +95,17 @@ spitfire_startup:
         membar          #Sync
 
 startup_continue:
-        wrpr            %g0, 15, %pil
-
         sethi           %hi(0x80000000), %g2
         sllx            %g2, 32, %g2
         wr              %g2, 0, %tick_cmpr
 
+        mov             %o0, %l0
+
         BRANCH_IF_SUN4V(g1, niagara_lock_tlb)
 
         /* Call OBP by hand to lock KERNBASE into i/d tlbs.
          * We lock 2 consequetive entries if we are 'bigkernel'.
          */
-        mov             %o0, %l0
-
         sethi           %hi(prom_entry_lock), %g2
 1:      ldstub          [%g2 + %lo(prom_entry_lock)], %g1
         membar          #StoreLoad | #StoreStore
@@ -112,7 +115,6 @@ startup_continue:
         sethi           %hi(p1275buf), %g2
         or              %g2, %lo(p1275buf), %g2
         ldx             [%g2 + 0x10], %l2
-        mov             %sp, %l1
         add             %l2, -(192 + 128), %sp
         flushw
 
@@ -308,18 +310,9 @@ niagara_lock_tlb:
         ta              HV_FAST_TRAP
 
 after_lock_tlb:
-        mov             %l1, %sp
-        flushw
-
-        mov             %l0, %o0
-
         wrpr            %g0, (PSTATE_PRIV | PSTATE_PEF), %pstate
         wr              %g0, 0, %fprs
 
-        /* XXX Buggy PROM... */
-        srl             %o0, 0, %o0
-        ldx             [%o0], %g6
-
         wr              %g0, ASI_P, %asi
 
         mov             PRIMARY_CONTEXT, %g7
@@ -341,22 +334,25 @@ after_lock_tlb:
 
         membar          #Sync
 
-        mov             1, %g5
-        sllx            %g5, THREAD_SHIFT, %g5
-        sub             %g5, (STACKFRAME_SZ + STACK_BIAS), %g5
-        add             %g6, %g5, %sp
+        /* Everything we do here, until we properly take over the
+         * trap table, must be done with extreme care.  We cannot
+         * make any references to %g6 (current thread pointer),
+         * %g4 (current task pointer), or %g5 (base of current cpu's
+         * per-cpu area) until we properly take over the trap table
+         * from the firmware and hypervisor.
+         *
+         * Get onto temporary stack which is in the locked kernel image.
+         */
+        sethi           %hi(tramp_stack), %g1
+        or              %g1, %lo(tramp_stack), %g1
+        add             %g1, TRAMP_STACK_SIZE, %g1
+        sub             %g1, STACKFRAME_SZ + STACK_BIAS, %sp
         mov             0, %fp
 
-        wrpr            %g0, 0, %wstate
-        wrpr            %g0, 0, %tl
-
-        /* Load TBA, then we can resurface. */
-        sethi           %hi(sparc64_ttable_tl0), %g5
-        wrpr            %g5, %tba
-
-        ldx             [%g6 + TI_TASK], %g4
-
-        wrpr            %g0, 0, %wstate
+        /* Put garbage in these registers to trap any access to them.  */
+        set             0xdeadbeef, %g4
+        set             0xdeadbeef, %g5
+        set             0xdeadbeef, %g6
 
         call            init_irqwork_curcpu
          nop
@@ -367,11 +363,17 @@ after_lock_tlb:
         bne,pt          %icc, 1f
          nop
 
+        call            hard_smp_processor_id
+         nop
+        
+        mov             %o0, %o1
+        mov             0, %o0
+        mov             0, %o2
         call            sun4v_init_mondo_queues
-         mov            0, %o0
+         mov            1, %o3
 
 1:      call            init_cur_cpu_trap
-         nop
+         ldx            [%l0], %o0
 
         /* Start using proper page size encodings in ctx register.  */
         sethi           %hi(sparc64_kern_pri_context), %g3
@@ -386,9 +388,14 @@ after_lock_tlb:
 
         membar          #Sync
 
-        rdpr            %pstate, %o1
-        or              %o1, PSTATE_IE, %o1
-        wrpr            %o1, 0, %pstate
+        wrpr            %g0, 0, %wstate
+
+        /* As a hack, put &init_thread_union into %g6.
+         * prom_world() loads from here to restore the %asi
+         * register.
+         */
+        sethi           %hi(init_thread_union), %g6
+        or              %g6, %lo(init_thread_union), %g6
 
         sethi           %hi(is_sun4v), %o0
         lduw            [%o0 + %lo(is_sun4v)], %o0
@@ -418,7 +425,20 @@ after_lock_tlb:
 1:      call            prom_set_trap_table
          sethi          %hi(sparc64_ttable_tl0), %o0
 
-2:      call            smp_callin
+2:      ldx             [%l0], %g6
+        ldx             [%g6 + TI_TASK], %g4
+
+        mov             1, %g5
+        sllx            %g5, THREAD_SHIFT, %g5
+        sub             %g5, (STACKFRAME_SZ + STACK_BIAS), %g5
+        add             %g6, %g5, %sp
+        mov             0, %fp
+
+        rdpr            %pstate, %o1
+        or              %o1, PSTATE_IE, %o1
+        wrpr            %o1, 0, %pstate
+
+        call            smp_callin
          nop
         call            cpu_idle
          mov            0, %o0