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Groups > linux.kernel > #1543461
| From | Geert Uytterhoeven <geert+renesas@glider.be> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option |
| Date | 2016-12-16 14:30 +0100 |
| Message-ID | <sP0Ke-4gJ-21@gated-at.bofh.it> (permalink) |
| References | <sP0Kd-4gJ-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
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>
---
v2:
- Change kernel parameter value from "nobounce" to "noforce",
- Extend swiotlb_force enum instead of adding swiotlb_nobounce
variable (both requested by Konrad Wilk).
---
Documentation/admin-guide/kernel-parameters.txt | 3 ++-
include/linux/swiotlb.h | 1 +
include/trace/events/swiotlb.h | 3 ++-
lib/swiotlb.c | 18 ++++++++++++++++--
4 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 21e2d88637050b7a..24fb691b2da5f78d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3811,10 +3811,11 @@
it if 0 is given (See Documentation/cgroup-v1/memory.txt)
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
- Format: { <int> | force }
+ Format: { <int> | force | noforce }
<int> -- Number of I/O TLB slabs
force -- force using of bounce buffers even if they
wouldn't be automatically used by the kernel
+ noforce -- Never use bounce buffers (for debugging)
switches= [HW,M68k]
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 71d104e4c8490763..d9c84a9cde3dd7d7 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -12,6 +12,7 @@
enum swiotlb_force {
SWIOTLB_NORMAL, /* Default - depending on HW DMA mask etc. */
SWIOTLB_FORCE, /* swiotlb=force */
+ SWIOTLB_NO_FORCE, /* swiotlb=noforce */
};
extern enum swiotlb_force swiotlb_force;
diff --git a/include/trace/events/swiotlb.h b/include/trace/events/swiotlb.h
index 5e2e30a7efce0ebd..288c0c54a2b4ace6 100644
--- a/include/trace/events/swiotlb.h
+++ b/include/trace/events/swiotlb.h
@@ -39,7 +39,8 @@
__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 */
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index a32dce6d5101f408..9def738af4f4e568 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -106,8 +106,12 @@
}
if (*str == ',')
++str;
- if (!strcmp(str, "force"))
+ if (!strcmp(str, "force")) {
swiotlb_force = SWIOTLB_FORCE;
+ } else if (!strcmp(str, "noforce")) {
+ swiotlb_force = SWIOTLB_NO_FORCE;
+ io_tlb_nslabs = 1;
+ }
return 0;
}
@@ -543,8 +547,15 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
map_single(struct device *hwdev, phys_addr_t phys, size_t size,
enum dma_data_direction dir, unsigned long attrs)
{
- dma_addr_t start_dma_addr = phys_to_dma(hwdev, io_tlb_start);
+ dma_addr_t start_dma_addr;
+
+ if (swiotlb_force == SWIOTLB_NO_FORCE) {
+ dev_warn_ratelimited(hwdev, "Cannot do DMA to address %pa\n",
+ &phys);
+ return SWIOTLB_MAP_ERROR;
+ }
+ start_dma_addr = phys_to_dma(hwdev, io_tlb_start);
return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size,
dir, attrs);
}
@@ -721,6 +732,9 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
swiotlb_full(struct device *dev, size_t size, enum dma_data_direction dir,
int do_panic)
{
+ if (swiotlb_force == SWIOTLB_NO_FORCE)
+ return;
+
/*
* Ran out of IOMMU space for this operation. This is very bad.
* Unfortunately the drivers cannot handle this operation properly.
--
1.9.1
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[PATCH v2 0/3] swiotlb: Add swiotlb=noforce debug option Geert Uytterhoeven <geert+renesas@glider.be> - 2016-12-16 14:30 +0100
[PATCH v2 2/3] swiotlb: Convert swiotlb_force from int to enum Geert Uytterhoeven <geert+renesas@glider.be> - 2016-12-16 14:30 +0100
[PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option Geert Uytterhoeven <geert+renesas@glider.be> - 2016-12-16 14:30 +0100
Re: [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option Konrad Rzeszutek Wilk <konrad@darnok.org> - 2016-12-19 14:40 +0100
Re: [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option Geert Uytterhoeven <geert@linux-m68k.org> - 2016-12-19 15:00 +0100
Re: [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-12-19 15:40 +0100
[PATCH v2 1/3] x86, swiotlb: Simplify pci_swiotlb_detect_override() Geert Uytterhoeven <geert+renesas@glider.be> - 2016-12-16 14:30 +0100
Re: [PATCH v2 0/3] swiotlb: Add swiotlb=noforce debug option Konrad Rzeszutek Wilk <konrad@darnok.org> - 2016-12-19 14:40 +0100
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