powerpc/mm/radix: Use the right page size for vmemmap mapping

We use mmu_vmemmap_psize to find the page size for mapping the vmmemap area.
With radix translation, we are suboptimally setting this value to PAGE_SIZE.

We do check for 2M page size support and update mmu_vmemap_psize to use
hugepage size but we suboptimally reset the value to PAGE_SIZE in
radix__early_init_mmu(). This resulted in always mapping vmemmap area with
64K page size.

Fixes: 2bfd65e4 ("powerpc/mm/radix: Add radix callbacks for early init routines")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/book3s64/radix_pgtable.c

@@ -520,14 +520,6 @@ void __init radix__early_init_devtree(void)
 	mmu_psize_defs[MMU_PAGE_64K].shift = 16;
 	mmu_psize_defs[MMU_PAGE_64K].ap = 0x5;
 found:
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-	if (mmu_psize_defs[MMU_PAGE_2M].shift) {
-		/*
-		 * map vmemmap using 2M if available
-		 */
-		mmu_vmemmap_psize = MMU_PAGE_2M;
-	}
-#endif /* CONFIG_SPARSEMEM_VMEMMAP */
 	return;
 }
 
@@ -592,7 +584,13 @@ void __init radix__early_init_mmu(void)
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 	/* vmemmap mapping */
-	mmu_vmemmap_psize = mmu_virtual_psize;
+	if (mmu_psize_defs[MMU_PAGE_2M].shift) {
+		/*
+		 * map vmemmap using 2M if available
+		 */
+		mmu_vmemmap_psize = MMU_PAGE_2M;
+	} else
+		mmu_vmemmap_psize = mmu_virtual_psize;
 #endif
 	/*
 	 * initialize page table size