linux-kernel - [PATCH 1/3] swiotlb: Export maximum allocation size

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Date:   Thu, 10 Jan 2019 14:44:31 +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>
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, hch@....de,
        Joerg Roedel <jroedel@...e.de>
Subject: [PATCH 1/3] swiotlb: Export maximum allocation size

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

The SWIOTLB implementation has a maximum size it can
allocate dma-handles for. This needs to be exported so that
device drivers don't try to allocate larger chunks.

This is especially important for block device drivers like
virtio-blk, that might do DMA through SWIOTLB.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 include/linux/swiotlb.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 7c007ed7505f..0bcc80a97036 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -72,6 +72,11 @@ static inline bool is_swiotlb_buffer(phys_addr_t paddr)
 	return paddr >= io_tlb_start && paddr < io_tlb_end;
 }
 
+static inline size_t swiotlb_max_alloc_size(void)
+{
+	return ((1UL << IO_TLB_SHIFT) * IO_TLB_SEGSIZE);
+}
+
 bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs);
 void __init swiotlb_exit(void);
@@ -95,6 +100,13 @@ static inline unsigned int swiotlb_max_segment(void)
 {
 	return 0;
 }
+
+static inline size_t swiotlb_max_alloc_size(void)
+{
+	/* There is no limit when SWIOTLB isn't used */
+	return ~0UL;
+}
+
 #endif /* CONFIG_SWIOTLB */
 
 extern void swiotlb_print_info(void);
-- 
2.17.1