Messages in this thread Patch in this message | | | Subject | Re: [PATCH 01/11] iommu: Add device dma ownership set/release interfaces | From | Lu Baolu <> | Date | Wed, 17 Nov 2021 13:22:19 +0800 |
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Hi Jason,
On 11/16/21 9:46 PM, Jason Gunthorpe wrote: > On Tue, Nov 16, 2021 at 09:57:30AM +0800, Lu Baolu wrote: >> Hi Christoph, >> >> On 11/15/21 9:14 PM, Christoph Hellwig wrote: >>> On Mon, Nov 15, 2021 at 10:05:42AM +0800, Lu Baolu wrote: >>>> +enum iommu_dma_owner { >>>> + DMA_OWNER_NONE, >>>> + DMA_OWNER_KERNEL, >>>> + DMA_OWNER_USER, >>>> +}; >>>> + >>> >>>> + enum iommu_dma_owner dma_owner; >>>> + refcount_t owner_cnt; >>>> + struct file *owner_user_file; >>> >>> I'd just overload the ownership into owner_user_file, >>> >>> NULL -> no owner >>> (struct file *)1UL) -> kernel >>> real pointer -> user >>> >>> Which could simplify a lot of the code dealing with the owner. >>> >> >> Yeah! Sounds reasonable. I will make this in the next version. > > It would be good to figure out how to make iommu_attach_device() > enforce no other driver binding as a kernel user without a file *, as > Robin pointed to, before optimizing this. > > This fixes an existing bug where iommu_attach_device() only checks the > group size and is vunerable to a hot plug increasing the group size > after it returns. That check should be replaced by this series's logic > instead.
As my my understanding, the essence of this problem is that only the user owner of the iommu_group could attach an UNMANAGED domain to it. If I understand it right, how about introducing a new interface to allocate a user managed domain and storing the user file pointer in it.
--- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -94,6 +94,7 @@ struct iommu_domain { void *handler_token; struct iommu_domain_geometry geometry; struct iommu_dma_cookie *iova_cookie; + struct file *owner_user_file; }; --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -1902,6 +1902,18 @@ struct iommu_domain *iommu_domain_alloc(struct bus_type *bus) } EXPORT_SYMBOL_GPL(iommu_domain_alloc);
+struct iommu_domain *iommu_domain_alloc_user(struct bus_type *bus, + struct file *filep) +{ + struct iommu_domain *domain; + + domain = __iommu_domain_alloc(bus, IOMMU_DOMAIN_UNMANAGED); + if (domain) + domain->owner_user_file = filep; + + return domain; +}
When attaching a domain to an user-owned iommu_group, both group and domain should have matched user fd.
Does above help here?
Best regards, baolu
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