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Commit 2b2b614d authored by Zoltan Kiss's avatar Zoltan Kiss Committed by Konrad Rzeszutek Wilk
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tracing/events: Add bounce tracing to swiotbl 



Ftrace is currently not able to detect when SWIOTLB has to do double buffering.
Under Xen you can only see it indirectly in function_graph, when
xen_swiotlb_map_page() doesn't stop after range_straddles_page_boundary(), but
calls spinlock functions, memcpy() and xen_phys_to_bus() as well. This patch
introduces the swiotlb:swiotlb_bounced event, which also prints out the
following informations to help you find out why bouncing happened:

dev_name: 0000:08:00.0 dma_mask=ffffffffffffffff dev_addr=9149f000 size=32768
swiotlb_force=0

If you use Xen, and (dev_addr + size + 1) > dma_mask, the buffer is out of the
device's DMA range. If swiotlb_force == 1, you should really change the kernel
parameters. Otherwise, the buffer is not contiguous in mfn space.

Signed-off-by: default avatarZoltan Kiss <zoltan.kiss@citrix.com>
[v1: Don't print 'swiotlb_force=X', just print swiotlb_force if it is enabled]
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 04b772d2

drivers/xen/swiotlb-xen.c

+5 −0
Original line number Diff line number Diff line
@@ -42,6 +42,9 @@ 
#include <xen/page.h>

#include <xen/xen-ops.h>

#include <xen/hvc-console.h>



#define CREATE_TRACE_POINTS

#include <trace/events/swiotlb.h>

/*

 * Used to do a quick range check in swiotlb_tbl_unmap_single and

 * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
@@ -358,6 +361,8 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page, 
	/*

	 * Oh well, have to allocate and map a bounce buffer.

	 */

	trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);



	map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir);

	if (map == SWIOTLB_MAP_ERROR)

		return DMA_ERROR_CODE;

include/trace/events/swiotlb.h

0 → 100644
+46 −0
Original line number Diff line number Diff line 
#undef TRACE_SYSTEM

#define TRACE_SYSTEM swiotlb



#if !defined(_TRACE_SWIOTLB_H) || defined(TRACE_HEADER_MULTI_READ)

#define _TRACE_SWIOTLB_H



#include <linux/tracepoint.h>



TRACE_EVENT(swiotlb_bounced,



	TP_PROTO(struct device *dev,

		 dma_addr_t dev_addr,

		 size_t size,

		 int swiotlb_force),



	TP_ARGS(dev, dev_addr, size, swiotlb_force),



	TP_STRUCT__entry(

		__string(	dev_name,	dev_name(dev)	)

		__field(	u64,	dma_mask		)

		__field(	dma_addr_t,	dev_addr	)

		__field(	size_t,	size			)

		__field(	int,	swiotlb_force		)

	),



	TP_fast_assign(

		__assign_str(dev_name, dev_name(dev));

		__entry->dma_mask = (dev->dma_mask ? *dev->dma_mask : 0);

		__entry->dev_addr = dev_addr;

		__entry->size = size;

		__entry->swiotlb_force = swiotlb_force;

	),



	TP_printk("dev_name: %s dma_mask=%llx dev_addr=%llx "

		"size=%zu %s",

		__get_str(dev_name),

		__entry->dma_mask,

		(unsigned long long)__entry->dev_addr,

		__entry->size,

		__entry->swiotlb_force ? "swiotlb_force" : "" )

);



#endif /*  _TRACE_SWIOTLB_H */



/* This part must be outside protection */

#include <trace/define_trace.h>

lib/swiotlb.c

+4 −0
Original line number Diff line number Diff line
@@ -38,6 +38,8 @@ 
#include <linux/bootmem.h>

#include <linux/iommu-helper.h>



#include <trace/events/swiotlb.h>



#define OFFSET(val,align) ((unsigned long)	\

	                   ( (val) & ( (align) - 1)))
@@ -726,6 +728,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page, 
	if (dma_capable(dev, dev_addr, size) && !swiotlb_force)

		return dev_addr;



	trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);



	/* Oh well, have to allocate and map a bounce buffer. */

	map = map_single(dev, phys, size, dir);

	if (map == SWIOTLB_MAP_ERROR) {