linux-kernel - Re: [PATCH 4/5] iommu: Make sure a device is always attached to a domain

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Date:	Wed, 28 Jan 2015 14:38:52 +0000
From:	Will Deacon <will.deacon@....com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Kukjin Kim <kgene@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Robin Murphy <Robin.Murphy@....com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	"jroedel@...e.de" <jroedel@...e.de>
Subject: Re: [PATCH 4/5] iommu: Make sure a device is always attached to a
 domain

On Tue, Jan 27, 2015 at 12:08:58AM +0000, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> Make use of the default domain and re-attach a device to it
> when it is detached from another domain. Also enforce that a
> device has to be in the default domain before it can be
> attached to a different domain.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  drivers/iommu/iommu.c | 34 +++++++++++++++++++++++++++++++---
>  1 file changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index b63a550..5080759 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -53,6 +53,7 @@ struct iommu_group {
>  	int id;
>  	unsigned dev_cnt;
>  	struct iommu_domain *default_domain;
> +	struct iommu_domain *domain;
>  };
>  
>  struct iommu_device {
> @@ -1040,8 +1041,17 @@ static int iommu_group_do_attach_device(struct device *dev, void *data)
>  
>  int iommu_attach_group(struct iommu_domain *domain, struct iommu_group *group)
>  {
> -	return iommu_group_for_each_dev(group, domain,
> -					iommu_group_do_attach_device);
> +	int ret;
> +
> +	if (group->default_domain && group->domain != group->default_domain)
> +		return -EBUSY;

I think this is now racy with itself and detach, whereas before we always
held the group->mutex by virtue of iommu_group_for_each_dev.

Will
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