From 8fb9f8d889b104a9acebaff83b637bcc56706576 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 19 Dec 2008 14:42:12 +0100 Subject: [PATCH] AMD IOMMU: reset command buffer pointers manually 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(+) diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c index a1378c4a79a1a..1226ec6e080c8 100644 --- 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(struct amd_iommu *iommu) 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; -- 2.47.3