This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: powerpc-powernv-ioda2-gracefully-fail-if-too-many-tce-levels-requested.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Tue Dec 12 13:26:17 CET 2017

From: Alexey Kardashevskiy aik@ozlabs.ru Date: Wed, 22 Feb 2017 15:43:59 +1100 Subject: powerpc/powernv/ioda2: Gracefully fail if too many TCE levels requested

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);

Patches currently in stable-queue which might be from aik@ozlabs.ru are

queue-4.9/powerpc-powernv-ioda2-gracefully-fail-if-too-many-tce-levels-requested.patch