xtensa: add alternative kernel memory layouts

MMUv3 is able to support low memory bigger than 128MB.
Implement 256MB and 512MB KSEG layouts:

- add Kconfig selector for KSEG layout;
- add KSEG base address, size and alignment definitions to
  arch/xtensa/include/asm/kmem_layout.h;
- use new definitions in TLB initialization;
- add build time memory map consistency checks.

See Documentation/xtensa/mmu.txt for the details of new memory layouts.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/xtensa/include/asm/highmem.h b/arch/xtensa/include/asm/highmem.h
index 01cef6b40829..6e070db1022e 100644
--- a/arch/xtensa/include/asm/highmem.h
+++ b/arch/xtensa/include/asm/highmem.h
@@ -68,6 +68,11 @@ void kunmap_high(struct page *page);
 
 static inline void *kmap(struct page *page)
 {
+	/* Check if this memory layout is broken because PKMAP overlaps
+	 * page table.
+	 */
+	BUILD_BUG_ON(PKMAP_BASE <
+		     XCHAL_PAGE_TABLE_VADDR + XCHAL_PAGE_TABLE_SIZE);
 	BUG_ON(in_interrupt());
 	if (!PageHighMem(page))
 		return page_address(page);