powerpc/mm: Add support for SPARSEMEM_VMEMMAP on 64-bit Book3E

The base TLB support didn't include support for SPARSEMEM_VMEMMAP, though
we did carve out some virtual space for it, the necessary support code
wasn't there. This implements it by using 16M pages for now, though the
page size could easily be changed at runtime if necessary.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
index d16100c9416..2fbc680c2c7 100644
--- a/arch/powerpc/mm/tlb_nohash.c
+++ b/arch/powerpc/mm/tlb_nohash.c
@@ -93,6 +93,7 @@ static inline int mmu_get_tsize(int psize)
 
 int mmu_linear_psize;           /* Page size used for the linear mapping */
 int mmu_pte_psize;              /* Page size used for PTE pages */
+int mmu_vmemmap_psize;          /* Page size used for the virtual mem map */
 int book3e_htw_enabled;         /* Is HW tablewalk enabled ? */
 unsigned long linear_map_top;   /* Top of linear mapping */
 
@@ -356,10 +357,18 @@ static void __early_init_mmu(int boot_cpu)
         unsigned int mas4;
 
         /* XXX This will have to be decided at runtime, but right
-         * now our boot and TLB miss code hard wires it
+         * now our boot and TLB miss code hard wires it. Ideally
+         * we should find out a suitable page size and patch the
+         * TLB miss code (either that or use the PACA to store
+         * the value we want)
          */
         mmu_linear_psize = MMU_PAGE_1G;
 
+        /* XXX This should be decided at runtime based on supported
+         * page sizes in the TLB, but for now let's assume 16M is
+         * always there and a good fit (which it probably is)
+         */
+        mmu_vmemmap_psize = MMU_PAGE_16M;
 
         /* Check if HW tablewalk is present, and if yes, enable it by:
          *