swiotlb: Add swiotlb=noforce debug option

commit fff5d99225107f5f13fe4a9805adc2a1c4b5fb00 upstream.

On architectures like arm64, swiotlb is tied intimately to the core
architecture DMA support. In addition, ZONE_DMA cannot be disabled.

To aid debugging and catch devices not supporting DMA to memory outside
the 32-bit address space, add a kernel command line option
"swiotlb=noforce", which disables the use of bounce buffers.
If specified, trying to map memory that cannot be used with DMA will
fail, and a rate-limited warning will be printed.

Note that io_tlb_nslabs is set to 1, which is the minimal supported
value.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/trace/events/swiotlb.h b/include/trace/events/swiotlb.h
index 5e2e30a7efce..288c0c54a2b4 100644
--- a/include/trace/events/swiotlb.h
+++ b/include/trace/events/swiotlb.h
@@ -39,7 +39,8 @@ TRACE_EVENT(swiotlb_bounced,
                 __entry->size,
                 __print_symbolic(__entry->swiotlb_force,
                         { SWIOTLB_NORMAL,       "NORMAL" },
-                        { SWIOTLB_FORCE,        "FORCE" }))
+                        { SWIOTLB_FORCE,        "FORCE" },
+                        { SWIOTLB_NO_FORCE,     "NO_FORCE" }))
 );
 
 #endif /*  _TRACE_SWIOTLB_H */