[PATCH 4.9 114/148] powerpc/powernv/ioda2: Gracefully fail if too many TCE levels requested

Greg Kroah-Hartman
2017-12-12T13:01:21Z

From: Alexey Kardashevskiy <aik@ozlabs.ru>

[ Upstream commit 7aafac11e308d37ed3c509829bb43d80c1811ac3 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/platforms/powernv/pci-ioda.c | 3 +++
1 file changed, 3 insertions(+)

--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2623,6 +2623,9 @@ static long pnv_pci_ioda2_table_alloc_pa
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);