[SPARC64]: Fix booting on non-zero cpu.

The early per-cpu handling needs a slight tweak to work when booting
on a non-zero cpu.

We got away with this for a long time, but can't any longer as now
even printk() calls functions (cpu_clock() for example) that thus make
early references to per-cpu variables.

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

2 files changed, 28 insertions, 0 deletions

diff --git a/arch/sparc64/kernel/head.S b/arch/sparc64/kernel/head.S
index c4147ad8677b..44b105c04dd3 100644
--- a/arch/sparc64/kernel/head.S
+++ b/arch/sparc64/kernel/head.S
@@ -632,11 +632,36 @@ tlb_fixup_done:
         /* Not reached... */
 
 1:
+        /* If we boot on a non-zero cpu, all of the per-cpu
+         * variable references we make before setting up the
+         * per-cpu areas will use a bogus offset.  Put a
+         * compensating factor into __per_cpu_base to handle
+         * this cleanly.
+         *
+         * What the per-cpu code calculates is:
+         *
+         *      __per_cpu_base + (cpu << __per_cpu_shift)
+         *
+         * These two variables are zero initially, so to
+         * make it all cancel out to zero we need to put
+         * "0 - (cpu << 0)" into __per_cpu_base so that the
+         * above formula evaluates to zero.
+         *
+         * We cannot even perform a printk() until this stuff
+         * is setup as that calls cpu_clock() which uses
+         * per-cpu variables.
+         */
+        sub     %g0, %o0, %o1
+        sethi   %hi(__per_cpu_base), %o2
+        stx     %o1, [%o2 + %lo(__per_cpu_base)]
 #else
         mov     0, %o0
 #endif
         sth     %o0, [%g6 + TI_CPU]
 
+        call    prom_init_report
+         nop
+
         /* Off we go.... */
         call    start_kernel
          nop
diff --git a/arch/sparc64/prom/init.c b/arch/sparc64/prom/init.c
index 1c0db842a6f4..87e7c7ea0ee6 100644
--- a/arch/sparc64/prom/init.c
+++ b/arch/sparc64/prom/init.c
@@ -48,7 +48,10 @@ void __init prom_init(void *cif_handler, void *cif_stack)
         prom_getstring(node, "version", prom_version, sizeof(prom_version));
 
         prom_printf("\n");
+}
 
+void __init prom_init_report(void)
+{
         printk("PROMLIB: Sun IEEE Boot Prom '%s'\n", prom_version);
         printk("PROMLIB: Root node compatible: %s\n", prom_root_compatible);
 }