Patch "powerpc/powernv/ioda2: Gracefully fail if too many TCE levels requested" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

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-4.4 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 13:38:50 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
@@ -2270,6 +2270,9 @@ 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-4.4/powerpc-powernv-ioda2-gracefully-fail-if-too-many-tce-levels-requested.patch