2.6.27-stable review patch. If anyone has any objections, please let us know. ------------------ From: Joerg Roedel Upstream commit cf558d25e5c9f70fa0279c9b7b8b4aed7cae9bd4 Under special circumstances the IOMMU does not reset the head and tail pointer of its command ringbuffer to zero when the command base is written. This causes the IOMMU to fetch random memory and executes it as an command. Since these commands are likely illegal IOMMU stops fetching further commands including IOTLB flushes. This leads to completion wait errors at boot and in some cases to data corruption and kernel crashes. Signed-off-by: Joerg Roedel Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/amd_iommu_init.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/x86/kernel/amd_iommu_init.c +++ b/arch/x86/kernel/amd_iommu_init.c @@ -407,6 +407,10 @@ static u8 * __init alloc_command_buffer( memcpy_toio(iommu->mmio_base + MMIO_CMD_BUF_OFFSET, &entry, sizeof(entry)); + /* set head and tail to zero manually */ + writel(0x00, iommu->mmio_base + MMIO_CMD_HEAD_OFFSET); + writel(0x00, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET); + iommu_feature_enable(iommu, CONTROL_CMDBUF_EN); return cmd_buf; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/