linux-kernel - [PATCH 2/5] swiotlb: Add is_swiotlb

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Date:   Tue, 29 Jan 2019 09:43:39 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>,
        virtualization@...ts.linux-foundation.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, jfehlig@...e.com,
        jon.grimm@....com, brijesh.singh@....com, joro@...tes.org,
        jroedel@...e.de
Subject: [PATCH 2/5] swiotlb: Add is_swiotlb_active() function

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

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@...cle.com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 include/linux/swiotlb.h | 6 ++++++
 kernel/dma/swiotlb.c    | 9 +++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 1c22d96e1742..e9e786b4b598 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -63,6 +63,7 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev,
 extern int
 swiotlb_dma_supported(struct device *hwdev, u64 mask);
 size_t swiotlb_max_mapping_size(struct device *dev);
+bool is_swiotlb_active(void);
 
 #ifdef CONFIG_SWIOTLB
 extern enum swiotlb_force swiotlb_force;
@@ -100,6 +101,11 @@ static inline size_t swiotlb_max_mapping_size(struct device *dev)
 {
 	return SIZE_MAX;
 }
+
+static inline bool is_swiotlb_active(void)
+{
+	return false;
+}
 #endif /* CONFIG_SWIOTLB */
 
 extern void swiotlb_print_info(void);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 9cb21259cb0b..c873f9cc2146 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -667,3 +667,12 @@ size_t swiotlb_max_mapping_size(struct device *dev)
 {
 	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;
+}
-- 
2.17.1