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powerpc/dma: Fix dma_map_ops::get_required_mask

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There are 2 problems with it:
  1. "<" vs expected "<<"
  2. the shift number is an IOMMU page number mask, not an address
  mask as the IOMMU page shift is missing.

This did not hit us before f1565c24b5 ("powerpc: use the generic
dma_ops_bypass mode") because we had additional code to handle bypass
mask so this chunk (almost?) never executed.However there were
reports that aacraid does not work with "iommu=nobypass".

After f1565c24b5, aacraid (and probably others which call
dma_get_required_mask() before setting the mask) was unable to enable
64bit DMA and fall back to using IOMMU which was known not to work,
one of the problems is double free of an IOMMU page.

This fixes DMA for aacraid, both with and without "iommu=nobypass" in
the kernel command line. Verified with "stress-ng -d 4".

Fixes: 6a5c7be5e4 ("powerpc: Override dma_get_required_mask by platform hook and ops")
Cc: stable@vger.kernel.org # v3.2+
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200908015106.79661-1-aik@ozlabs.ru
This commit is contained in:
Alexey Kardashevskiy 2020-09-08 11:51:06 +10:00 committed by Michael Ellerman
parent 4c62285439
commit 437ef802e0
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/kernel/dma-iommu.c
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@ -120,7 +120,8 @@ u64 dma_iommu_get_required_mask(struct device *dev)
if (!tbl)
return 0;
mask = 1ULL < (fls_long(tbl->it_offset + tbl->it_size) - 1);
mask = 1ULL << (fls_long(tbl->it_offset + tbl->it_size) +
tbl->it_page_shift - 1);
mask += mask - 1;
return mask;