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powerpc/powernv/ioda2: Gracefully fail if too many TCE levels requested

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The IODA2 specification says that a 64 DMA address cannot use top 4 bits
(3 are reserved and one is a "TVE select"); bottom page_shift bits
cannot be used for multilevel table addressing either.

The existing IODA2 table allocation code aligns the minimum TCE table
size to PAGE_SIZE so in the case of 64K system pages and 4K IOMMU pages,
we have 64-4-12=48 bits. Since 64K page stores 8192 TCEs, i.e. needs
13 bits, the maximum number of levels is 48/13 = 3 so we physically
cannot address more and EEH happens on DMA accesses.

This adds a check that too many levels were requested.

It is still possible to have 5 levels in the case of 4K system page size.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Alexey Kardashevskiy 2017-02-22 15:43:59 +11:00 committed by Michael Ellerman
parent 605df8d674
commit 7aafac11e3
1 changed files with 3 additions and 0 deletions
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arch/powerpc/platforms/powernv/pci-ioda.c
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@ -2624,6 +2624,9 @@ static long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
level_shift = entries_shift + 3;
level_shift = max_t(unsigned, level_shift, PAGE_SHIFT);
if ((level_shift - 3) * levels + page_shift >= 60)
return -EINVAL;
/* Allocate TCE table */
addr = pnv_pci_ioda2_table_do_alloc_pages(nid, level_shift,
levels, tce_table_size, &offset, &total_allocated);