Messages in this thread | | | Date | Mon, 11 Sep 2023 20:46:26 +0800 | Subject | Re: [PATCH v4 09/10] iommu: Make iommu_queue_iopf() more generic | From | Baolu Lu <> |
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On 2023/9/11 14:57, Tian, Kevin wrote: >> From: Baolu Lu <baolu.lu@linux.intel.com> >> Sent: Tuesday, September 5, 2023 1:24 PM >> >> Hi Kevin, >> >> I am trying to address this issue in below patch. Does it looks sane to >> you? >> >> iommu: Consolidate per-device fault data management >> >> The per-device fault data is a data structure that is used to store >> information about faults that occur on a device. This data is allocated >> when IOPF is enabled on the device and freed when IOPF is disabled. The >> data is used in the paths of iopf reporting, handling, responding, and >> draining. >> >> The fault data is protected by two locks: >> >> - dev->iommu->lock: This lock is used to protect the allocation and >> freeing of the fault data. >> - dev->iommu->fault_parameter->lock: This lock is used to protect the >> fault data itself. >> >> Improve the iopf code to enforce this lock mechanism and add a reference >> counter in the fault data to avoid use-after-free issue. >> > > Can you elaborate the use-after-free issue and why a new user count > is required?
I was concerned that when iommufd uses iopf, page fault report/response may occur simultaneously with enable/disable PRI.
Currently, this is not an issue as the enable/disable PRI is in its own path. In the future, we may discard this interface and enable PRI when attaching the first PRI-capable domain, and disable it when detaching the last PRI-capable domain.
> > btw a Fix tag is required given this mislocking issue has been there for > quite some time...
I don't see any real issue fixed by this change. It's only a lock refactoring after the code refactoring and preparing it for iommufd use. Perhaps I missed anything?
Best regards, baolu
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