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swiotlb: Return consistent SWIOTLB segments/nr_tbl 

With a specifically contrived memory layout where there is no physical
memory available to the kernel below the 4GB boundary, we will fail to
perform the initial swiotlb_init() call and set no_iotlb_memory to true.

There are drivers out there that call into swiotlb_nr_tbl() to determine
whether they can use the SWIOTLB. With the right DMA_BIT_MASK() value
for these drivers (say 64-bit), they won't ever need to hit
swiotlb_tbl_map_single() so this can go unoticed and we would be
possibly lying about those drivers.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Florian Fainelli 2019-06-11 10:58:25 -07:00 committed by Konrad Rzeszutek Wilk
parent 0bfaffbf4c
commit 4aa095ea32
1 changed files with 4 additions and 4 deletions
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8
kernel/dma/swiotlb.c
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@ -128,15 +128,17 @@ setup_io_tlb_npages(char *str)
} }
early_param("swiotlb", setup_io_tlb_npages); early_param("swiotlb", setup_io_tlb_npages);
static bool no_iotlb_memory;
unsigned long swiotlb_nr_tbl(void) unsigned long swiotlb_nr_tbl(void)
{ {
return io_tlb_nslabs; return unlikely(no_iotlb_memory) ? 0 : io_tlb_nslabs;
} }
EXPORT_SYMBOL_GPL(swiotlb_nr_tbl); EXPORT_SYMBOL_GPL(swiotlb_nr_tbl);
unsigned int swiotlb_max_segment(void) unsigned int swiotlb_max_segment(void)
{ {
return max_segment; return unlikely(no_iotlb_memory) ? 0 : max_segment;
} }
EXPORT_SYMBOL_GPL(swiotlb_max_segment); EXPORT_SYMBOL_GPL(swiotlb_max_segment);
@ -159,8 +161,6 @@ unsigned long swiotlb_size_or_default(void)
return size ? size : (IO_TLB_DEFAULT_SIZE); return size ? size : (IO_TLB_DEFAULT_SIZE);
} }
static bool no_iotlb_memory;
void swiotlb_print_info(void) void swiotlb_print_info(void)
{ {
unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT; unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;