linux-kernel - Re: [PATCH] iommu: Check for deferred attach in iommu_group_do_dma

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Date:   Thu, 4 Jun 2020 11:39:36 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH] iommu: Check for deferred attach in
 iommu_group_do_dma_attach()

On Thu, Jun 04, 2020 at 11:19:44AM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> The iommu_group_do_dma_attach() must not attach devices which have
> deferred_attach set. Otherwise devices could cause IOMMU faults when
> re-initialized in a kdump kernel.
> 
> Fixes: deac0b3bed26 ("iommu: Split off default domain allocation from group assignment")
> Reported-by: Jerry Snitselaar <jsnitsel@...hat.com>
> Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
> Tested-by: Jerry Snitselaar <jsnitsel@...hat.com>
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  drivers/iommu/iommu.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index b5ea203f6c68..5a6d509f72b6 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1680,8 +1680,12 @@ static void probe_alloc_default_domain(struct bus_type *bus,
>  static int iommu_group_do_dma_attach(struct device *dev, void *data)
>  {
>  	struct iommu_domain *domain = data;
> +	int ret = 0;
>  
> -	return __iommu_attach_device(domain, dev);
> +	if (!iommu_is_attach_deferred(group->domain, dev))
> +		ret = __iommu_attach_device(group->domain, dev);

And of course with the same bug as my original diff. Fixed that up
before applying it. (group->domain -> domain).


	Joerg