Hi Julien,
Julien Grall <jul...@xen.org> writes: > On 16/11/2023 15:26, Stewart Hildebrand wrote: >> On 11/16/23 10:12, Julien Grall wrote: >>> Hi Volodymyr, >>> >>> On 16/11/2023 15:07, Volodymyr Babchuk wrote: >>>> With my vPCI patch series in place, hypervisor itself assigns BDFs for >>>> passed-through devices. Toolstack needs to get this information to know >>>> which BDFs are free and can be used by virtio-pci. >>> >>> It sounds a bit odd to let the hypervisor to assign the BDFs. At >>> least because there might be case where you want to specific vBDF >>> (for instance this is the case with some intel graphic cards). This >>> should be the toolstack job to say "I want to assign the pBDF to >>> this vBDF". >> Keep in mind we are also supporting dom0less PCI passthrough. > Right, but even with that in mind, I expect the Device-Tree to provide > the details where a given PCI is assigned. > > You could have logic for assigning the BDF automagically. But that > should be part of dom0less, not deep into the vPCI code. As far as I know, right now toolstack does not allow you to assign BDF in any form. For x86 there are two options, and they are controlled by "passthrough" option of xen-pciback driver in Linux: "Option to specify how to export PCI topology to guest:" " 0 - (default) Hide the true PCI topology and makes the frontend" " there is a single PCI bus with only the exported devices on it." " For example, a device at 03:05.0 will be re-assigned to 00:00.0" " while second device at 02:1a.1 will be re-assigned to 00:01.1." " 1 - Passthrough provides a real view of the PCI topology to the" " frontend (for example, a device at 06:01.b will still appear at" " 06:01.b to the frontend). This is similar to how Xen 2.0.x" " exposed PCI devices to its driver domains. This may be required" " for drivers which depend on finding their hardward in certain" " bus/slot locations."); Also, isn't strict dependency on BDF breaks the PCI specification? I mean, of course, you can assign Function on random, but what about Bus and Device parts? I mean, we can make toolstack responsible of assigning BDFs, but this might break existing x86 setups... -- WBR, Volodymyr
