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dma: swiotlb: Track whether the pool size was explicitly set

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swiotlb_adjust_size() must not override a pool size supplied through the
swiotlb= command-line parameter.

Currently, it determines whether a size was supplied by comparing
default_nslabs with IO_TLB_DEFAULT_SIZE. This fails when the user
explicitly requests the compiled-in default size, allowing the request
to be overwritten by automatic pool sizing.

Record whether swiotlb= supplied a numeric size in swiotlb_cmdline_size_set
and check that flag directly before adjusting the pool size.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
Link: https://lore.kernel.org/r/20260924060756.1325156-4-aneesh.kumar@kernel.org
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Aneesh Kumar K.V (Arm) 2026-09-24 11:37:51 +05:30 committed by Marek Szyprowski
parent d5093dbca7
commit af3857eac7
1 changed files with 3 additions and 1 deletions
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4
kernel/dma/swiotlb.c
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@ -100,6 +100,7 @@ static struct io_tlb_mem io_tlb_default_mem;
static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
static unsigned long default_nareas;
static bool swiotlb_cmdline_size_set __initdata;
/**
* struct io_tlb_area - IO TLB memory area descriptor
@ -253,6 +254,7 @@ setup_io_tlb_npages(char *str)
/* avoid tail segment of size < IO_TLB_SEGSIZE */
default_nslabs =
ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
swiotlb_cmdline_size_set = true;
}
if (*str == ',')
++str;
@ -295,7 +297,7 @@ void __init swiotlb_adjust_size(unsigned long size)
* architectures such as those supporting memory encryption to
* adjust/expand SWIOTLB size for their use.
*/
if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
if (swiotlb_cmdline_size_set)
return;
default_nslabs = swiotlb_calc_nslabs(size, default_nareas);