Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init() in Linux 3.4

Joerg Roedel
2013-02-06T12:12:29Z

On Tue, Feb 05, 2013 at 06:57:21AM -0700, Shuah Khan wrote:
> Thanks much. I will hang on to this test system for testing your fix.

Okay, here is the simple fix for v3.8-rc6. I guess it is not
straighforward to port it to v3.4, but it should be doable.

>From 2ecf57c85e67e0243b36b787d0490c0b47202ba8 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <joro@8bytes.org>
Date: Wed, 6 Feb 2013 12:55:23 +0100
Subject: [PATCH] iommu/amd: Initialize device table after dma_ops

When dma_ops are initialized the unity mappings are
created. The init_device_table_dma() function makes sure DMA
from all devices is blocked by default. This opens a short
window in time where DMA to unity mapped regions is blocked
by the IOMMU. Make sure this does not happen by initializing
the device table after dma_ops.

Signed-off-by: Joerg Roedel <joro@8bytes.org>
---
drivers/iommu/amd_iommu_init.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index faf10ba..b6ecddb 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1876,11 +1876,6 @@ static int amd_iommu_init_dma(void)
struct amd_iommu *iommu;
int ret;

- init_device_table_dma();
-
- for_each_iommu(iommu)
- iommu_flush_all_caches(iommu);
-
if (iommu_pass_through)
ret = amd_iommu_init_passthrough();
else
@@ -1889,6 +1884,11 @@ static int amd_iommu_init_dma(void)
if (ret)
return ret;

+ init_device_table_dma();
+
+ for_each_iommu(iommu)
+ iommu_flush_all_caches(iommu);
+
amd_iommu_init_api();

amd_iommu_init_notifier();
--
1.7.9.5