On Tue, Sep 23, 2025 at 11:30:41AM -0600, Alex Williamson wrote:
On Tue, 23 Sep 2025 12:04:14 -0300 Jason Gunthorpe jgg@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.
I agree it is a weird interface, but it is close to the existing weird interface :\
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.
It uses devm to call pci_p2pdma_release() which NULL's pdev->p2pdma.
Jason