From: Joerg Roedel <jroedel@suse.de>
Date: Thu, 7 Feb 2019 12:59:14 +0100
Subject: swiotlb: Add is_swiotlb_active() function
Git-commit: 492366f7b4237257ef50ca9c431a6a0d50225aca
Patch-mainline: v5.1-rc1
References: bsc#1120008

This function will be used from dma_direct code to determine
the maximum segment size of a dma mapping.

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/linux/swiotlb.h | 6 ++++++
 kernel/dma/swiotlb.c    | 9 +++++++++
 2 files changed, 15 insertions(+)

--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -117,6 +117,7 @@ swiotlb_dma_supported(struct device *hwd
 extern void __init swiotlb_free(void);
 unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
+bool is_swiotlb_active(void);
 #else
 static inline void swiotlb_free(void) { }
 static inline unsigned int swiotlb_max_segment(void) { return 0; }
@@ -124,6 +125,10 @@ static inline size_t swiotlb_max_mapping
 {
 	return SIZE_MAX;
 }
+static inline bool is_swiotlb_active(void)
+{
+	return false;
+}
 #endif
 
 extern void swiotlb_print_info(void);
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -1093,3 +1093,13 @@ size_t swiotlb_max_mapping_size(struct d
 	return ((size_t)1 << IO_TLB_SHIFT) * IO_TLB_SEGSIZE;
 }
 EXPORT_SYMBOL(swiotlb_max_mapping_size);
+
+bool is_swiotlb_active(void)
+{
+	/*
+	 * When SWIOTLB is initialized, even if io_tlb_start points to physical
+	 * address zero, io_tlb_end surely doesn't.
+	 */
+	return io_tlb_end != 0;
+}
+EXPORT_SYMBOL(is_swiotlb_active);