On Sun, Oct 20, 2024 at 10:21:29PM -0700, Vivek Kasireddy wrote: > Functions of the same PCI device (such as a PF and a VF) share the > same bus and have a common root port and typically, the PF provisions > resources for the VF. Therefore, they can be considered compatible > as far as P2P access is considered. > > Currently, although the distance (2) is correctly calculated for > functions of the same device, an ACS check failure prevents P2P DMA > access between them. Therefore, introduce a small function named > pci_devs_are_p2pdma_compatible() to determine if the provider and > client belong to the same device and facilitate P2P DMA between > them by not enforcing the ACS check. > > v2: > - Relax the enforcment of ACS check only for Intel GPU functions > as they are P2PDMA compatible given the way the PF provisions > the resources among multiple VFs. I don't want version history in the commit log. If the content is useful, just incorporate it here directly (without the version info), and put the version-to-version changelog below the "---". > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx> > Cc: <linux-pci@xxxxxxxxxxxxxxx> > Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx> > --- > drivers/pci/p2pdma.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 4f47a13cb500..a230e661f939 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -535,6 +535,17 @@ static unsigned long map_types_idx(struct pci_dev *client) > return (pci_domain_nr(client->bus) << 16) | pci_dev_id(client); > } > > +static bool pci_devs_are_p2pdma_compatible(struct pci_dev *provider, > + struct pci_dev *client) > +{ > + if (provider->vendor == PCI_VENDOR_ID_INTEL) { > + if (pci_is_vga(provider) && pci_is_vga(client)) > + return pci_physfn(provider) == pci_physfn(client); > + } This doesn't explain why this should be specific to Intel or VGA. As far as I can tell, everything mentioned in the commit log is generic. I see the previous comments (https://lore.kernel.org/all/eddb423c-945f-40c9-b904-43ea8371f1c4@xxxxxxxxxxxx/), but none of that context was captured here. I'm not sure what you refer to by "PF provisions resources for the VF". Isn't it *always* the case that the architected PCI resources (BARs) are configured by the PF? It sounds like you're referring to something Intel GPU-specific beyond that? > + return false; > +} > + > /* > * Calculate the P2PDMA mapping type and distance between two PCI devices. > * > @@ -634,7 +645,7 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, > > *dist = dist_a + dist_b; > > - if (!acs_cnt) { > + if (!acs_cnt || pci_devs_are_p2pdma_compatible(provider, client)) { > map_type = PCI_P2PDMA_MAP_BUS_ADDR; > goto done; > } > @@ -696,7 +707,9 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients, > return -1; > > for (i = 0; i < num_clients; i++) { > - pci_client = find_parent_pci_dev(clients[i]); > + pci_client = dev_is_pf(clients[i]) ? > + pci_dev_get(to_pci_dev(clients[i])) : > + find_parent_pci_dev(clients[i]); > if (!pci_client) { > if (verbose) > dev_warn(clients[i], > -- > 2.45.1 >