linux-kernel - Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu

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Message-ID: <20130206121223.GT25591@8bytes.org>
Date:	Wed, 6 Feb 2013 13:12:23 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Shuah Khan <shuahkhan@...il.com>
Cc:	Shuah Khan <shuah.khan@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	stable <stable@...r.kernel.org>, iommu@...ts.linux-foundation.org
Subject: Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init()
 in Linux 3.4

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@...tes.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@...tes.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


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