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Date:   Sun, 31 Jul 2022 20:10:06 +0800
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Subject: Re: [PATCH v10 04/12] iommu: Add attach/detach_dev_pasid iommu
 interface
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To:     Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        "Will Deacon" <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        "Jean-Philippe Brucker" <jean-philippe@linaro.com>,
        Dave Jiang <dave.jiang@intel.com>,
        "Vinod Koul" <vkoul@kernel.org>
CC:     Eric Auger <eric.auger@redhat.com>,
        Jacob jun Pan <jacob.jun.pan@intel.com>,
        Zhangfei Gao <zhangfei.gao@linaro.org>,
        Zhu Tony <tony.zhu@intel.com>, <iommu@lists.linux.dev>,
        <linux-kernel@vger.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>
References: <20220705050710.2887204-1-baolu.lu@linux.intel.com>
 <20220705050710.2887204-5-baolu.lu@linux.intel.com>
From:   Yi Liu <yi.l.liu@intel.com>
In-Reply-To: <20220705050710.2887204-5-baolu.lu@linux.intel.com>
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On 2022/7/5 13:07, Lu Baolu wrote:
> Attaching an IOMMU domain to a PASID of a device is a generic operation
> for modern IOMMU drivers which support PASID-granular DMA address
> translation. Currently visible usage scenarios include (but not limited):

s/visible/known/? "known" seems better. up to you. :-)

> 
>   - SVA (Shared Virtual Address)
>   - kernel DMA with PASID
>   - hardware-assist mediated device
> 
> This adds a pair of domain ops for this purpose and adds the interfaces
> for device drivers to attach/detach a domain to/from a {device, PASID}.
> Some buses, like PCI, route packets without considering the PASID value.
> Thus a DMA target address with PASID might be treated as P2P if the
> address falls into the MMIO BAR of other devices in the group. To make
> things simple, these interfaces only apply to devices belonging to the
> singleton groups, and the singleton is immutable in fabric (i.e. not
> affected by hotplug).
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
> Tested-by: Tony Zhu <tony.zhu@intel.com>
> ---
>   include/linux/iommu.h | 21 ++++++++++++
>   drivers/iommu/iommu.c | 75 +++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 96 insertions(+)

Reviewed-by: Yi Liu <yi.l.liu@intel.com>

> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index f41eb2b3c7da..f2b5aa7efe43 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -262,6 +262,8 @@ struct iommu_ops {
>    * struct iommu_domain_ops - domain specific operations
>    * @attach_dev: attach an iommu domain to a device
>    * @detach_dev: detach an iommu domain from a device
> + * @set_dev_pasid: set an iommu domain to a pasid of device
> + * @block_dev_pasid: block pasid of device from using iommu domain
>    * @map: map a physically contiguous memory region to an iommu domain
>    * @map_pages: map a physically contiguous set of pages of the same size to
>    *             an iommu domain.
> @@ -282,6 +284,10 @@ struct iommu_ops {
>   struct iommu_domain_ops {
>   	int (*attach_dev)(struct iommu_domain *domain, struct device *dev);
>   	void (*detach_dev)(struct iommu_domain *domain, struct device *dev);
> +	int (*set_dev_pasid)(struct iommu_domain *domain, struct device *dev,
> +			     ioasid_t pasid);
> +	void (*block_dev_pasid)(struct iommu_domain *domain, struct device *dev,
> +				ioasid_t pasid);
>   
>   	int (*map)(struct iommu_domain *domain, unsigned long iova,
>   		   phys_addr_t paddr, size_t size, int prot, gfp_t gfp);
> @@ -679,6 +685,10 @@ int iommu_group_claim_dma_owner(struct iommu_group *group, void *owner);
>   void iommu_group_release_dma_owner(struct iommu_group *group);
>   bool iommu_group_dma_owner_claimed(struct iommu_group *group);
>   
> +int iommu_attach_device_pasid(struct iommu_domain *domain, struct device *dev,
> +			      ioasid_t pasid);
> +void iommu_detach_device_pasid(struct iommu_domain *domain, struct device *dev,
> +			       ioasid_t pasid);
>   #else /* CONFIG_IOMMU_API */
>   
>   struct iommu_ops {};
> @@ -1052,6 +1062,17 @@ static inline bool iommu_group_dma_owner_claimed(struct iommu_group *group)
>   {
>   	return false;
>   }
> +
> +static inline int iommu_attach_device_pasid(struct iommu_domain *domain,
> +					    struct device *dev, ioasid_t pasid)
> +{
> +	return -ENODEV;
> +}
> +
> +static inline void iommu_detach_device_pasid(struct iommu_domain *domain,
> +					     struct device *dev, ioasid_t pasid)
> +{
> +}
>   #endif /* CONFIG_IOMMU_API */
>   
>   /**
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 74a0a3ec0907..be48b09371f4 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -39,6 +39,7 @@ struct iommu_group {
>   	struct kobject kobj;
>   	struct kobject *devices_kobj;
>   	struct list_head devices;
> +	struct xarray pasid_array;
>   	struct mutex mutex;
>   	void *iommu_data;
>   	void (*iommu_data_release)(void *iommu_data);
> @@ -660,6 +661,7 @@ struct iommu_group *iommu_group_alloc(void)
>   	mutex_init(&group->mutex);
>   	INIT_LIST_HEAD(&group->devices);
>   	INIT_LIST_HEAD(&group->entry);
> +	xa_init(&group->pasid_array);
>   
>   	ret = ida_alloc(&iommu_group_ida, GFP_KERNEL);
>   	if (ret < 0) {
> @@ -3271,3 +3273,76 @@ bool iommu_group_dma_owner_claimed(struct iommu_group *group)
>   	return user;
>   }
>   EXPORT_SYMBOL_GPL(iommu_group_dma_owner_claimed);
> +
> +static bool iommu_group_immutable_singleton(struct iommu_group *group,
> +					    struct device *dev)
> +{
> +	int count;
> +
> +	mutex_lock(&group->mutex);
> +	count = iommu_group_device_count(group);
> +	mutex_unlock(&group->mutex);
> +
> +	if (count != 1)
> +		return false;
> +
> +	/*
> +	 * The PCI device could be considered to be fully isolated if all
> +	 * devices on the path from the device to the host-PCI bridge are
> +	 * protected from peer-to-peer DMA by ACS.
> +	 */
> +	if (dev_is_pci(dev))
> +		return pci_acs_path_enabled(to_pci_dev(dev), NULL,
> +					    REQ_ACS_FLAGS);
> +
> +	/*
> +	 * Otherwise, the device came from DT/ACPI, assume it is static and
> +	 * then singleton can know from the device count in the group.
> +	 */
> +	return true;
> +}
> +
> +int iommu_attach_device_pasid(struct iommu_domain *domain, struct device *dev,
> +			      ioasid_t pasid)
> +{
> +	struct iommu_group *group;
> +	void *curr;
> +	int ret;
> +
> +	if (!domain->ops->set_dev_pasid)
> +		return -EOPNOTSUPP;
> +
> +	group = iommu_group_get(dev);
> +	if (!group || !iommu_group_immutable_singleton(group, dev)) {
> +		iommu_group_put(group);
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&group->mutex);
> +	curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, domain, GFP_KERNEL);
> +	if (curr) {
> +		ret = xa_err(curr) ? : -EBUSY;
> +		goto out_unlock;
> +	}
> +	ret = domain->ops->set_dev_pasid(domain, dev, pasid);
> +	if (ret)
> +		xa_erase(&group->pasid_array, pasid);
> +out_unlock:
> +	mutex_unlock(&group->mutex);
> +	iommu_group_put(group);
> +
> +	return ret;
> +}
> +
> +void iommu_detach_device_pasid(struct iommu_domain *domain, struct device *dev,
> +			       ioasid_t pasid)
> +{
> +	struct iommu_group *group = iommu_group_get(dev);
> +
> +	mutex_lock(&group->mutex);
> +	domain->ops->block_dev_pasid(domain, dev, pasid);
> +	xa_erase(&group->pasid_array, pasid);
> +	mutex_unlock(&group->mutex);
> +
> +	iommu_group_put(group);
> +}

-- 
Regards,
Yi Liu