linux-kernel - Re: [PATCH 3/4] iommu: Introduce IOMMU call-back for processing struct KVM assigned to VFIO

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Message-ID: <e4d5db37-a7b9-9b33-4ecf-c168b6d41a9a@arm.com>
Date:   Tue, 10 Jan 2023 15:11:23 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Cc:     joro@...tes.org, ashish.kalra@....com, thomas.lendacky@....com,
        vasant.hegde@....com, jon.grimm@....com
Subject: Re: [PATCH 3/4] iommu: Introduce IOMMU call-back for processing
 struct KVM assigned to VFIO

On 2023-01-10 14:31, Suravee Suthikulpanit wrote:
> Currently, VFIO provide an kvm_vfio_file_set_kvm() interface for assigning
> a KVM structure to a VFIO group. The information in struct KVM is also
> useful for IOMMU drivers when setting up VFIO domain.
> 
> Introduce struct iommu_domain_ops.set_kvm call-back function to allow
> IOMMU drivers to provide call-back to process the struct KVM assigned.

Hmm, it sounds like this has quite some overlap of intent with the 
existing "enable_nesting" op, and my gut feeling is that it's not great 
to have two completely different "this is a VFIO domain" mechanisms... :/

Robin.

> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>   drivers/iommu/iommu.c    | 10 ++++++++++
>   drivers/vfio/vfio_main.c |  1 +
>   include/linux/iommu.h    |  4 ++++
>   3 files changed, 15 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 65a3b3d886dc..5116d5fe35f2 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -3231,3 +3231,13 @@ bool iommu_group_dma_owner_claimed(struct iommu_group *group)
>   	return user;
>   }
>   EXPORT_SYMBOL_GPL(iommu_group_dma_owner_claimed);
> +
> +void iommu_set_kvm(struct iommu_group *group, struct kvm *kvm)
> +{
> +	if (!group || !group->domain || !group->domain->ops)
> +		return;
> +
> +	if (group->domain->ops->set_kvm)
> +		group->domain->ops->set_kvm(group->domain, kvm);
> +}
> +EXPORT_SYMBOL_GPL(iommu_set_kvm);
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 2d168793d4e1..7641e3a0c986 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -1652,6 +1652,7 @@ void vfio_file_set_kvm(struct file *file, struct kvm *kvm)
>   
>   	mutex_lock(&group->group_lock);
>   	group->kvm = kvm;
> +	iommu_set_kvm(group->iommu_group, kvm);
>   	mutex_unlock(&group->group_lock);
>   }
>   EXPORT_SYMBOL_GPL(vfio_file_set_kvm);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 3c9da1f8979e..43000231d3d7 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -42,6 +42,7 @@ struct notifier_block;
>   struct iommu_sva;
>   struct iommu_fault_event;
>   struct iommu_dma_cookie;
> +struct kvm;
>   
>   /* iommu fault flags */
>   #define IOMMU_FAULT_READ	0x0
> @@ -314,6 +315,8 @@ struct iommu_domain_ops {
>   				  unsigned long quirks);
>   
>   	void (*free)(struct iommu_domain *domain);
> +
> +	void (*set_kvm)(struct iommu_domain *domain, struct kvm *kvm);
>   };
>   
>   /**
> @@ -391,6 +394,7 @@ void iommu_device_sysfs_remove(struct iommu_device *iommu);
>   int  iommu_device_link(struct iommu_device   *iommu, struct device *link);
>   void iommu_device_unlink(struct iommu_device *iommu, struct device *link);
>   int iommu_deferred_attach(struct device *dev, struct iommu_domain *domain);
> +void iommu_set_kvm(struct iommu_group *group, struct kvm *kvm);
>   
>   static inline struct iommu_device *dev_to_iommu_device(struct device *dev)
>   {