Re: [PATCH v5 03/12] iommu: Add attach/detach_dev_pasid domain ops

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2022/5/4 02:07, Jean-Philippe Brucker wrote:
> On Mon, May 02, 2022 at 09:48:33AM +0800, 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):
>>
>>   - SVA (Shared Virtual Address)
>>   - kernel DMA with PASID
>>   - hardware-assist mediated device
>>
>> This adds a pair of common domain ops for this purpose and adds helpers
>> 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>
> 
> just a nit below
> 
>> ---
>>   include/linux/iommu.h | 21 ++++++++++++
>>   drivers/iommu/iommu.c | 76 +++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 97 insertions(+)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index b8ffaf2cb1d0..ab36244d4e94 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -263,6 +263,8 @@ 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
>> + * @attach_dev_pasid: attach an iommu domain to a pasid of device
>> + * @detach_dev_pasid: detach an iommu domain from a pasid of device
>>    * @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.
>> @@ -283,6 +285,10 @@ 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 (*attach_dev_pasid)(struct iommu_domain *domain,
>> +				struct device *dev, ioasid_t pasid);
>> +	void (*detach_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);
>> @@ -678,6 +684,10 @@ 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 {};
>> @@ -1051,6 +1061,17 @@ 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 29906bc16371..89c9d19ddb28 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -38,6 +38,7 @@ 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);
>> @@ -630,6 +631,7 @@ 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_simple_get(&iommu_group_ida, 0, 0, GFP_KERNEL);
>>   	if (ret < 0) {
>> @@ -3190,3 +3192,77 @@ bool iommu_group_dma_owner_claimed(struct iommu_group *group)
>>   	return user;
>>   }
>>   EXPORT_SYMBOL_GPL(iommu_group_dma_owner_claimed);
>> +
>> +/*
>> + * Use standard PCI bus topology and isolation features to check immutable
>> + * singleton. Otherwise, assume the bus is static and then singleton can
>> + * know from the device count in the group.
>> + */
> 
> The comment doesn't really add anything that can't be directly understood
> from the code.

Yes. It's fine to remove it.

Best regards,
baolu
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