Messages in this thread | | | Subject | Re: [PATCH 01/11] iommu: Add device dma ownership set/release interfaces | From | Lu Baolu <> | Date | Thu, 18 Nov 2021 09:12:41 +0800 |
| |
On 11/17/21 9:35 PM, Jason Gunthorpe wrote: > On Wed, Nov 17, 2021 at 01:22:19PM +0800, Lu Baolu wrote: >> 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. > > For iommu_attach_device() the semantic is simple non-sharing, so there > is no need for the file * at all, it can just be NULL.
The file * being NULL means the device is only owned by the kernel driver. Perhaps we can check this pointer in iommu_attach_device() to avoid using it for user domain attachment.
> >> Does above help here? > > No, iommu_attach_device() is kernel only and should not interact with > userspace.
The existing iommu_attach_device() allows only for singleton group. As we have added group ownership attribute, we can enforce this interface only for kernel domain usage.
> > I'm also going to see if I can learn what Tegra is doing with > iommu_attach_group()
Okay! Thank you!
> > Jason >
Best regards, baolu
| |