memblock, nobootmem: add memblock_virt_alloc_low()

The new memblock_virt APIs are used to replaced old bootmem API.

We need to allocate page below 4G for swiotlb.

That should fix regression on Andrew's system that is using swiotlb.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 2e1c102..b604b83 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -172,7 +172,7 @@
 	/*
 	 * Get the overflow emergency buffer
 	 */
-	v_overflow_buffer = memblock_virt_alloc_nopanic(
+	v_overflow_buffer = memblock_virt_alloc_low_nopanic(
 						PAGE_ALIGN(io_tlb_overflow),
 						PAGE_SIZE);
 	if (!v_overflow_buffer)
@@ -220,7 +220,7 @@
 	bytes = io_tlb_nslabs << IO_TLB_SHIFT;
 
 	/* Get IO TLB memory from the low pages */
-	vstart = memblock_virt_alloc_nopanic(PAGE_ALIGN(bytes), PAGE_SIZE);
+	vstart = memblock_virt_alloc_low_nopanic(PAGE_ALIGN(bytes), PAGE_SIZE);
 	if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose))
 		return;