linux-kernel - Re: [PATCH 3.2] iommu/amd: Initialize device table after dma

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Message-ID: <1362265235.3768.156.camel@deadeye.wl.decadent.org.uk>
Date:	Sat, 02 Mar 2013 23:00:35 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	shuah.khan@...com
Cc:	Joerg Roedel <joro@...tes.org>, iommu@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>,
	stable <stable@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>, shuahkhan@...il.com
Subject: Re: [PATCH 3.2] iommu/amd: Initialize device table after dma_ops

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@...tes.org>
> Signed-off-by: Shuah Khan <shuah.khan@...com>
> CC: stable@...r.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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