Messages in this thread | | | Subject | Re: [PATCH v3 01/18] iommu: Add device dma ownership set/release interfaces | From | Lu Baolu <> | Date | Tue, 7 Dec 2021 10:07:16 +0800 |
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On 12/6/21 10:42 PM, Christoph Hellwig wrote: > On Mon, Dec 06, 2021 at 09:58:46AM +0800, Lu Baolu wrote: >> >From the perspective of who is initiating the device to do DMA, device >> DMA could be divided into the following types: >> >> DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver >> through the kernel DMA API. >> DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel >> driver with its own PRIVATE domain. >> DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by >> userspace. >> >> Different DMA ownerships are exclusive for all devices in the same iommu >> group as an iommu group is the smallest granularity of device isolation >> and protection that the IOMMU subsystem can guarantee. This extends the >> iommu core to enforce this exclusion. >> >> Basically two new interfaces are provided: >> >> int iommu_device_set_dma_owner(struct device *dev, >> enum iommu_dma_owner type, void *owner_cookie); >> void iommu_device_release_dma_owner(struct device *dev, >> enum iommu_dma_owner type); >> >> Although above interfaces are per-device, DMA owner is tracked per group >> under the hood. An iommu group cannot have different dma ownership set >> at the same time. Violation of this assumption fails >> iommu_device_set_dma_owner(). >> >> Kernel driver which does DMA have DMA_OWNER_DMA_API automatically set/ >> released in the driver binding/unbinding process (see next patch). >> >> Kernel driver which doesn't do DMA could avoid setting the owner type. >> Device bound to such driver is considered same as a driver-less device >> which is compatible to all owner types. >> >> Userspace driver framework (e.g. vfio) should set >> DMA_OWNER_PRIVATE_DOMAIN_USER for a device before the userspace is allowed >> to access it, plus a owner cookie pointer to mark the user identity so a >> single group cannot be operated by multiple users simultaneously. Vice >> versa, the owner type should be released after the user access permission >> is withdrawn. >> >> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> >> Signed-off-by: Kevin Tian <kevin.tian@intel.com> >> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> >> --- >> include/linux/iommu.h | 36 +++++++++++++++++ >> drivers/iommu/iommu.c | 93 +++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 129 insertions(+) >> >> diff --git a/include/linux/iommu.h b/include/linux/iommu.h >> index d2f3435e7d17..24676b498f38 100644 >> --- a/include/linux/iommu.h >> +++ b/include/linux/iommu.h >> @@ -162,6 +162,23 @@ enum iommu_dev_features { >> IOMMU_DEV_FEAT_IOPF, >> }; >> >> +/** >> + * enum iommu_dma_owner - IOMMU DMA ownership >> + * @DMA_OWNER_NONE: No DMA ownership. >> + * @DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver through >> + * the kernel DMA API. >> + * @DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel driver >> + * which provides an UNMANAGED domain. >> + * @DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by userspace, >> + * kernel ensures that DMAs never go to kernel memory. >> + */ >> +enum iommu_dma_owner { >> + DMA_OWNER_NONE, >> + DMA_OWNER_DMA_API, >> + DMA_OWNER_PRIVATE_DOMAIN, >> + DMA_OWNER_PRIVATE_DOMAIN_USER, >> +}; >> + >> #define IOMMU_PASID_INVALID (-1U) >> >> #ifdef CONFIG_IOMMU_API >> @@ -681,6 +698,10 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, >> void iommu_sva_unbind_device(struct iommu_sva *handle); >> u32 iommu_sva_get_pasid(struct iommu_sva *handle); >> >> +int iommu_device_set_dma_owner(struct device *dev, enum iommu_dma_owner owner, >> + void *owner_cookie); >> +void iommu_device_release_dma_owner(struct device *dev, enum iommu_dma_owner owner); >> + >> #else /* CONFIG_IOMMU_API */ >> >> struct iommu_ops {}; >> @@ -1081,6 +1102,21 @@ static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device *dev) >> { >> return NULL; >> } >> + >> +static inline int iommu_device_set_dma_owner(struct device *dev, >> + enum iommu_dma_owner owner, >> + void *owner_cookie) >> +{ >> + if (owner != DMA_OWNER_DMA_API) >> + return -EINVAL; >> + >> + return 0; >> +} >> + >> +static inline void iommu_device_release_dma_owner(struct device *dev, >> + enum iommu_dma_owner owner) >> +{ >> +} >> #endif /* CONFIG_IOMMU_API */ >> >> /** >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index 8b86406b7162..1de520a07518 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -48,6 +48,9 @@ struct iommu_group { >> struct iommu_domain *default_domain; >> struct iommu_domain *domain; >> struct list_head entry; >> + enum iommu_dma_owner dma_owner; >> + refcount_t owner_cnt; > > owner_cnt is only manipulated under group->mutex, not need for a > refcount_t here, a plain unsigned int while do it and will also > simplify a fair bit of code as it avoid the need for atomic add/sub > and test operations.
Fair enough.
> >> +static int __iommu_group_set_dma_owner(struct iommu_group *group, >> + enum iommu_dma_owner owner, >> + void *owner_cookie) >> +{ > > As pointed out last time, please move the group->mutex locking into > this helper, which makes it identical to the later added public > function.
I didn't mean to ignore your comment. :-) As I replied, by placing the lock out of the function, the helper could easily handle the error paths (return directly without something like "goto out_unlock").
As the implementation of iommu_group_set_dma_owner() has been greatly simplified, I agree with you now, we should move the group->mutex locking into the helper and make it identical to the latter public interface.
I will work towards this.
> >> +static void __iommu_group_release_dma_owner(struct iommu_group *group, >> + enum iommu_dma_owner owner) >> +{ > > Same here. >
Ditto.
Best regards, baolu
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