This is a note to let you know that I've just added the patch titled
iommu/amd: Only unmap large pages from the first pte
to the 3.4-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:
iommu-amd-only-unmap-large-pages-from-the-first-pte.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 60d0ca3cfd199b6612bbbbf4999a3470dad38bb1 Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@xxxxxxxxxx>
Date: Fri, 21 Jun 2013 14:33:19 -0600
Subject: iommu/amd: Only unmap large pages from the first pte
From: Alex Williamson <alex.williamson@xxxxxxxxxx>
commit 60d0ca3cfd199b6612bbbbf4999a3470dad38bb1 upstream.
If we use a large mapping, the expectation is that only unmaps from
the first pte in the superpage are supported. Unmaps from offsets
into the superpage should fail (ie. return zero sized unmap). In the
current code, unmapping from an offset clears the size of the full
mapping starting from an offset. For instance, if we map a 16k
physically contiguous range at IOVA 0x0 with a large page, then
attempt to unmap 4k at offset 12k, 4 ptes are cleared (12k - 28k) and
the unmap returns 16k unmapped. This potentially incorrectly clears
valid mappings and confuses drivers like VFIO that use the unmap size
to release pinned pages.
Fix by refusing to unmap from offsets into the page.
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Joerg Roedel <joro@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/iommu/amd_iommu.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1309,6 +1309,10 @@ static unsigned long iommu_unmap_page(st
/* Large PTE found which maps this address */
unmap_size = PTE_PAGE_SIZE(*pte);
+
+ /* Only unmap from the first pte in the page */
+ if ((unmap_size - 1) & bus_addr)
+ break;
count = PAGE_SIZE_PTE_COUNT(unmap_size);
for (i = 0; i < count; i++)
pte[i] = 0ULL;
@@ -1318,7 +1322,7 @@ static unsigned long iommu_unmap_page(st
unmapped += unmap_size;
}
- BUG_ON(!is_power_of_2(unmapped));
+ BUG_ON(unmapped && !is_power_of_2(unmapped));
return unmapped;
}
Patches currently in stable-queue which might be from alex.williamson@xxxxxxxxxx are
queue-3.4/iommu-amd-only-unmap-large-pages-from-the-first-pte.patch
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