On Wed, Mar 30, 2022 at 08:53:16AM -0400, Peter Xu wrote: > On Wed, Mar 30, 2022 at 11:04:24AM +0100, Stefan Hajnoczi wrote: > > This makes me wonder whether there is a deeper issue with the > > pci_setup_iommu() API: the lack of per-device cleanup callbacks. > > Per-device IOMMU resources should be freed when a device is hot > > unplugged. > > > > From what I can tell this is not the case today: > > > > - hw/i386/intel_iommu.c:vtd_find_add_as() allocates and adds device > > address spaces but I can't find where they are removed and freed. > > VTDAddressSpace instances pointed to from vtd_bus->dev_as[] are leaked. > > > > - hw/i386/amd_iommu.c has similar leaks. > > AFAICT it's because there's no device-specific data cached in the > per-device IOMMU address space, at least so far. IOW, all the data > structures allocated here can be re-used when a new device is plugged in > after the old device unplugged. > > It's definitely not ideal since after unplug (and before a new device > plugged in) the resource is not needed at all so it's kind of wasted, but > it should work functionally. If to achieve that, some iommu_unplug() or > iommu_cleanup() hook sounds reasonable.
I guess the question is whether PCI busses can be hotplugged with IOMMUs. If yes, then there is a memory leak that matters for intel_iommu.c and amd_iommu.c. Stefan
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