powerpc/mm: Add support for handling > 512TB address in SLB miss

For addresses above 512TB we allocate additional mmu contexts. To make
it all easy, addresses above 512TB are handled with IR/DR=1 and with
stack frame setup.

The mmu_context_t is also updated to track the new extended_ids. To
support upto 4PB we need a total 8 contexts.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Minor formatting tweaks and comment wording, switch BUG to WARN
      in get_ea_context().]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 14 insertions, 1 deletions

diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 09ac1a709d0c..9cd87d11fe4e 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -648,6 +648,15 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 	slice_print_mask(" mask", &potential_mask);
 
  convert:
+	/*
+	 * Try to allocate the context before we do slice convert
+	 * so that we handle the context allocation failure gracefully.
+	 */
+	if (need_extra_context(mm, newaddr)) {
+		if (alloc_extended_context(mm, newaddr) < 0)
+			return -ENOMEM;
+	}
+
 	slice_andnot_mask(&potential_mask, &potential_mask, &good_mask);
 	if (compat_maskp && !fixed)
 		slice_andnot_mask(&potential_mask, &potential_mask, compat_maskp);
@@ -658,10 +667,14 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 		if (psize > MMU_PAGE_BASE)
 			on_each_cpu(slice_flush_segments, mm, 1);
 	}
+	return newaddr;
 
 return_addr:
+	if (need_extra_context(mm, newaddr)) {
+		if (alloc_extended_context(mm, newaddr) < 0)
+			return -ENOMEM;
+	}
 	return newaddr;
-
 }
 EXPORT_SYMBOL_GPL(slice_get_unmapped_area);