On Tue, May 06, 2025 at 09:58:47AM -0300, Jason Gunthorpe wrote: > On Mon, May 05, 2025 at 07:53:44PM -0700, Nicolin Chen wrote: > > On Mon, May 05, 2025 at 02:08:07PM -0300, Jason Gunthorpe wrote: > > > On Wed, Apr 30, 2025 at 12:58:47AM -0700, Nicolin Chen wrote: > > > The bus numbers can be reassigned at any time on the fly by the guest > > > by reprogramming the PCI hierarchy. > > > > Yes. If we take some aggressive use case into account, where its > > BDF number could change multiple times, I think it's natural for > > VMM to simply destroy the previous vDEVICE and allocate a new one > > with a new BDF number, right? > > We should not destroy the vdevice for something like that. In a CC > case that would unplug it from the VM which is not right.
CC needs BDF to allocate a VDEV in the CC world. So, it cannot allocate a VDEV with BDF=0 firstly, which is what Alex reported. And even for a normal case that the device is migrating between PCI buses, CC might not be able to update the BDF (which can be a part of CC_VDEV_ALLOC instruction), even if iommufd supports an update ioctl. So, the underlying handler for an update ioctl is still to first destroy the VDEV and re-allocate a new one? Thanks Nicolin
