On Fri, Sep 19, 2025 at 08:33:23AM +0100, Will Deacon wrote: > pieces and will need to work on the userspace side. It's not like > MSI_IOVA2 is magically going to work (and I bet it won't be tested).
It could, if someone checks the default memory map a second constant could be selected that works. > > Nicolin has some patches on the iommufd side to let userspace select > > the MSI address instead, but they are not done yet. > > Maybe we should just wait for that? Carrying a temporary hack with ABI > implications to support broken hardware isn't particularly compelling > to me. This patch would still be needed for kernel users. Arguably the kernel users should just be using the iova allocator from dma-iommu.c. This whole hard coded constant/sneaky uapi is just a hack to make vfio work.. So maybe if the single constant doesn't work we could set some indication that the caller must allocate the MSI iova, the kernel can use the dma-iommu allocator and VFIO can just refuse to use the device for now. Jason
