> From: Tian, Kevin > Sent: Thursday, November 2, 2023 10:52 AM > > > > > Without an in-tree user of this code, we're just chopping up code for > > no real purpose. There's no reason that a variant driver requiring IMS > > couldn't initially implement their own SET_IRQS ioctl. Doing that > > this is an interesting idea. We haven't seen a real usage which wants > such MSI emulation on IMS for variant drivers. but if the code is > simple enough to demonstrate the 1st user of IMS it might not be > a bad choice. There are additional trap-emulation required in the > device MMIO bar (mostly copying MSI permission entry which contains > PASID info to the corresponding IMS entry). At a glance that area > is 4k-aligned so should be doable. > misread the spec. the MSI-X permission table which provides auxiliary data to MSI-X table is not 4k-aligned. It sits in the 1st 4k page together with many other registers. emulation of them could be simple with a native read/write handler but not sure whether any of them may sit in a hot path to affect perf due to trap...
