powerpc/mm/book3s64: Make KERN_IO_START a variable

Currently KERN_IO_START is defined as:

 #define KERN_IO_START  (KERN_VIRT_START + (KERN_VIRT_SIZE >> 1))

Although it looks like a constant, both the components are actually
variables, to allow us to have a different value between Radix and
Hash with a single kernel.

However that still requires both Radix and Hash to place the kernel IO
region at the same location relative to the start and end of the
kernel virtual region (namely 1/2 way through it), and we'd like to
change that.

So split KERN_IO_START out into its own variable, and initialise it
for Radix and Hash. In the medium term we should be able to
reconsolidate this, by doing a more involved rearrangement of the
location of the regions.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

3 files changed, 4 insertions, 0 deletions

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 7419fc1..a93137c 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1019,6 +1019,7 @@ void __init hash__early_init_mmu(void)
 	__kernel_virt_size = H_KERN_VIRT_SIZE;
 	__vmalloc_start = H_VMALLOC_START;
 	__vmalloc_end = H_VMALLOC_END;
+	__kernel_io_start = H_KERN_IO_START;
 	vmemmap = (struct page *)H_VMEMMAP_BASE;
 	ioremap_bot = IOREMAP_BASE;
 
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index 5d05245..c1185c8 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c
@@ -494,6 +494,7 @@ void __init radix__early_init_mmu(void)
 	__kernel_virt_size = RADIX_KERN_VIRT_SIZE;
 	__vmalloc_start = RADIX_VMALLOC_START;
 	__vmalloc_end = RADIX_VMALLOC_END;
+	__kernel_io_start = RADIX_KERN_IO_START;
 	vmemmap = (struct page *)RADIX_VMEMMAP_BASE;
 	ioremap_bot = IOREMAP_BASE;
 
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 0736e94..ac0717a 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -104,6 +104,8 @@ unsigned long __vmalloc_start;
 EXPORT_SYMBOL(__vmalloc_start);
 unsigned long __vmalloc_end;
 EXPORT_SYMBOL(__vmalloc_end);
+unsigned long __kernel_io_start;
+EXPORT_SYMBOL(__kernel_io_start);
 struct page *vmemmap;
 EXPORT_SYMBOL(vmemmap);
 unsigned long __pte_frag_nr;