On Tue, 23 Sep 2025 12:04:14 -0300 Jason Gunthorpe <j...@nvidia.com> wrote:
> On Mon, Sep 22, 2025 at 03:00:32PM -0600, Alex Williamson wrote: > > But then later in patch 8/ and again in 10/ why exactly do we cache > > the provider on the vfio_pci_core_device rather than ask for it on > > demand from the p2pdma? > > It makes the most sense if the P2P is activated once during probe(), > it is just a cheap memory allocation, so no reason not to. > > If you try to do it on-demand then it will require more locking. I'm only wondering about splitting to an "initialize/setup" function where providers for each BAR are setup, and a "get provider" interface, which doesn't really seem to be a hot path anyway. Batching could still be done to setup all BAR providers at once. However, the setup isn't really once per probe(), even in the case of a new driver probing we re-use the previously setup providers. Doesn't that introduce a problem that the provider bus_offset can be stale if something like a BAR resize has occurred between drivers? Possibly the providers should be setup in PCI core, a re-init triggered for resource updates, and the driver interface is only to get the provider. Thanks, Alex
