linux-kernel - [PATCH 5.0 126/238] swiotlb: Add is_swiotlb

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Date:   Fri, 22 Mar 2019 12:15:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Christoph Hellwig <hch@....de>, Joerg Roedel <jroedel@...e.de>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: [PATCH 5.0 126/238] swiotlb: Add is_swiotlb_active() function

5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joerg Roedel <jroedel@...e.de>

commit 492366f7b4237257ef50ca9c431a6a0d50225aca upstream.

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

Cc: stable@...r.kernel.org
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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
@@ -77,6 +77,7 @@ bool swiotlb_map(struct device *dev, phy
 void __init swiotlb_exit(void);
 unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
+bool is_swiotlb_active(void);
 #else
 #define swiotlb_force SWIOTLB_NO_FORCE
 static inline bool is_swiotlb_buffer(phys_addr_t paddr)
@@ -100,6 +101,11 @@ static inline size_t swiotlb_max_mapping
 {
 	return SIZE_MAX;
 }
+
+static inline bool is_swiotlb_active(void)
+{
+	return false;
+}
 #endif /* CONFIG_SWIOTLB */
 
 extern void swiotlb_print_info(void);
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -667,3 +667,12 @@ size_t swiotlb_max_mapping_size(struct d
 {
 	return ((size_t)1 << IO_TLB_SHIFT) * IO_TLB_SEGSIZE;
 }
+
+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;
+}