Re: [PATCH 5/6] iommu/amd: Lock dev_data in attach/detach code paths

["Sironi, Filippo via iommu" <iommu@lists.linux-foundation.org>]

> On 25. Sep 2019, at 06:22, Joerg Roedel <joro@8bytes.org> wrote:
> 
> From: Joerg Roedel <jroedel@suse.de>
> 
> Make sure that attaching a detaching a device can't race against each
> other and protect the iommu_dev_data with a spin_lock in these code
> paths.
> 
> Fixes: 92d420ec028d ("iommu/amd: Relax locking in dma_ops path")
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> drivers/iommu/amd_iommu.c       | 9 +++++++++
> drivers/iommu/amd_iommu_types.h | 3 +++
> 2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 459247c32dc0..bac4e20a5919 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -201,6 +201,7 @@ static struct iommu_dev_data *alloc_dev_data(u16 devid)
> 	if (!dev_data)
> 		return NULL;
> 
> +	spin_lock_init(&dev_data->lock);
> 	dev_data->devid = devid;
> 	ratelimit_default_init(&dev_data->rs);
> 
> @@ -2157,6 +2158,8 @@ static int attach_device(struct device *dev,
> 
> 	dev_data = get_dev_data(dev);
> 
> +	spin_lock(&dev_data->lock);
> +
> 	ret = -EBUSY;
> 	if (dev_data->domain != NULL)
> 		goto out;
> @@ -2199,6 +2202,8 @@ static int attach_device(struct device *dev,
> 	domain_flush_complete(domain);
> 
> out:
> +	spin_unlock(&dev_data->lock);
> +
> 	spin_unlock_irqrestore(&domain->lock, flags);
> 
> 	return ret;
> @@ -2218,6 +2223,8 @@ static void detach_device(struct device *dev)
> 
> 	spin_lock_irqsave(&domain->lock, flags);
> 
> +	spin_lock(&dev_data->lock);
> +
> 	/*
> 	 * First check if the device is still attached. It might already
> 	 * be detached from its domain because the generic
> @@ -2240,6 +2247,8 @@ static void detach_device(struct device *dev)
> 	dev_data->ats.enabled = false;
> 
> out:
> +	spin_unlock(&dev_data->lock);
> +
> 	spin_unlock_irqrestore(&domain->lock, flags);
> }
> 
> diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h
> index 0186501ab971..c9c1612d52e0 100644
> --- a/drivers/iommu/amd_iommu_types.h
> +++ b/drivers/iommu/amd_iommu_types.h
> @@ -633,6 +633,9 @@ struct devid_map {
>  * This struct contains device specific data for the IOMMU
>  */
> struct iommu_dev_data {
> +	/*Protect against attach/detach races */
> +	spinlock_t lock;
> +
> 	struct list_head list;		  /* For domain->dev_list */
> 	struct llist_node dev_data_list;  /* For global dev_data_list */
> 	struct protection_domain *domain; /* Domain the device is bound to */
> -- 
> 2.17.1
> 

Reviewed-by: Filippo Sironi <sironi@amazon.de>



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