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authorThadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>2011-09-20 03:07:24 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2011-09-23 10:27:03 +1000
commitd12b524f8b2f4e45cabe8bc1501e8b967d543111 (patch)
treef19127f7d644ed9f009466aad57bceb8e0404f15 /arch
parent25c29f9e3242071bca1bee7ad919baf1888ae436 (diff)
downloadlinux-d12b524f8b2f4e45cabe8bc1501e8b967d543111.tar.bz2
powerpc: Reserve iommu page 0
Some devices have a dma-window that starts at the address 0. This allows DMA addresses to be mapped to this address and returned to drivers as a valid DMA address. Some drivers may not behave well in this case, since the address 0 is considered an error or not allocated. The solution to avoid this kind of error from happening is reserve the page addressed as 0 so it cannot be allocated for a DMA mapping. Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kernel/iommu.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 961bb03413f3..0cfcf98aafca 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -501,6 +501,14 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
tbl->it_map = page_address(page);
memset(tbl->it_map, 0, sz);
+ /*
+ * Reserve page 0 so it will not be used for any mappings.
+ * This avoids buggy drivers that consider page 0 to be invalid
+ * to crash the machine or even lose data.
+ */
+ if (tbl->it_offset == 0)
+ set_bit(0, tbl->it_map);
+
tbl->it_hint = 0;
tbl->it_largehint = tbl->it_halfpoint;
spin_lock_init(&tbl->it_lock);