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

Baolu Lu
2022-05-05T06:31:01Z

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