Re: [PATCH 3.2] iommu/amd: Initialize device table after dma_ops

Ben Hutchings
2013-03-02T23:00:51Z

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On Thu, 2013-02-28 at 14:39 -0700, Shuah Khan wrote:
> 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.
>
> Back-port upstream commit: f528d980c17b8714aedc918ba86e058af914d66b
> Tested on 3.2.38
>
> Signed-off-by: Joerg Roedel <joro@8bytes.org>
> Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> CC: stable@vger.kernel.org 3.2

I'm not convinced about this backport, because the order of
initialisation already changed a lot after 3.2 and before the upstream
commit. So I'm going to wait for Joerg to confirm that this makes sense
before adding it to the patch queue.

Ben.

> ---
> drivers/iommu/amd_iommu_init.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
> index 62a4d5c..b7d1cdd 100644
> --- a/drivers/iommu/amd_iommu_init.c
> +++ b/drivers/iommu/amd_iommu_init.c
> @@ -1396,6 +1396,7 @@ static struct syscore_ops amd_iommu_syscore_ops = {
> */
> static int __init amd_iommu_init(void)
> {
> + struct amd_iommu *iommu;
> int i, ret = 0;
>
> /*
> @@ -1444,9 +1445,6 @@ static int __init amd_iommu_init(void)
> if (amd_iommu_pd_alloc_bitmap == NULL)
> goto free;
>
> - /* init the device table */
> - init_device_table();
> -
> /*
> * let all alias entries point to itself
> */
> @@ -1496,6 +1494,12 @@ static int __init amd_iommu_init(void)
> if (ret)
> goto free_disable;
>
> + /* init the device table */
> + init_device_table();
> +
> + for_each_iommu(iommu)
> + iommu_flush_all_caches(iommu);
> +
> amd_iommu_init_api();
>
> amd_iommu_init_notifier();

--
Ben Hutchings
Computers are not intelligent. They only think they are.

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