On Thu, Nov 03, 2022 at 12:32:53PM +0200, Mika Westerberg wrote: > It is possible to have PCIe switch upstream port a multifunction device. I can't quite parse this. I guess the point is that a Switch Upstream Port may be one of the functions of a multifunction device? > The resource distribution code does not take this into account properly > and therefore it expands the upstream port resource windows too much, > not leaving space for the other functions (in the multifunction device) > and this leads to an issue that Jonathan reported. He runs QEMU with > the following topoology (QEMU parameters): > > -device pcie-root-port,port=0,id=root_port13,chassis=0,slot=2 \ > -device x3130-upstream,id=sw1,bus=root_port13,multifunction=on \ > -device e1000,bus=root_port13,addr=0.1 \ > -device xio3130-downstream,id=fun1,bus=sw1,chassis=0,slot=3 \ > -device e1000,bus=fun1 > > The first e1000 NIC here is another function in the switch upstream > port. This leads to following errors: > > pci 0000:00:04.0: bridge window [mem 0x10200000-0x103fffff] to [bus 02-04] > pci 0000:02:00.0: bridge window [mem 0x10200000-0x103fffff] to [bus 03-04] > pci 0000:02:00.1: BAR 0: failed to assign [mem size 0x00020000] > e1000 0000:02:00.1: can't ioremap BAR 0: [??? 0x00000000 flags 0x0] > > Fix this by taking into account the possible multifunction devices when > uptream port resources are distributed. Can you include the link to Jonathan's report? > Reported-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > --- > Hi, > > This is the formal patch that resulted from the discussion here: > > https://lore.kernel.org/linux-pci/20220905080232.36087-5-mika.westerberg@xxxxxxxxxxxxxxx/T/#m724289d0ee0c1ae07628744c283116e60efaeaf1 > > Only change from that version is that we loop through all resources of > the multifunction device. > > drivers/pci/setup-bus.c | 63 ++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 59 insertions(+), 4 deletions(-) > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c > index b4096598dbcb..c8787b187ee4 100644 > --- a/drivers/pci/setup-bus.c > +++ b/drivers/pci/setup-bus.c > @@ -1830,10 +1830,65 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus, > * bridges below. > */ > if (hotplug_bridges + normal_bridges == 1) { > - dev = list_first_entry(&bus->devices, struct pci_dev, bus_list); > - if (dev->subordinate) > - pci_bus_distribute_available_resources(dev->subordinate, > - add_list, io, mmio, mmio_pref); > + /* Upstream port must be the first */ Do you have any citation or reasoning for this handy? We had this assumption before, and it seems true that an Upstream Port must be Function 0 because a variety of Link-related things have to be in Function 0, e.g., ARI ASPM Control, ARI Clock PM, Autonomous Width Disable, Flit Mode Disable, LTR Enable, OBFF Enable, etc. But those are all pretty oblique. I guess it's better to have the comment than not, but is the sort of assertion that makes one wonder why it is true. > + bridge = list_first_entry(&bus->devices, struct pci_dev, bus_list); > + if (!bridge->subordinate) > + return; > + > + /* > + * It is possible to have switch upstream port as a part > + * of a multifunction device. For this reason reduce the > + * resources occupied by the other functions before > + * distributing the rest. The space consumed by the peer functions of the Switch Upstream Port is determined by their BAR sizes, so I don't think we actually reduce that. I *think* the point here is to reduce the space available for distribution by the amount required by the peers of the Switch Upstream Port, right? I.e., "mmio" is the amount of space we have to distribute, and before splitting it across devices on the secondary bus, we need to save out the space required for peers on the primary bus. > + */ > + list_for_each_entry(dev, &bus->devices, bus_list) { > + int i; > + > + if (dev == bridge) > + continue; > + > + /* > + * It should be multifunction but if not stop > + * the distribution and bail out. > + */ > + if (!dev->multifunction) > + return; Why do we bother with this? If there are multiple devices on the bus, don't we want to consider them all, regardless of whether dev->multifunction is set? It seems like a gratuitous check. > + for (i = 0; i < PCI_NUM_RESOURCES; i++) { > + const struct resource *dev_res = &dev->resource[i]; > + resource_size_t dev_sz; > + struct resource *b_res; > + > + if (dev_res->flags & IORESOURCE_IO) { > + b_res = &io; > + } else if (dev_res->flags & IORESOURCE_MEM) { > + if (dev_res->flags & IORESOURCE_PREFETCH) > + b_res = &mmio_pref; > + else > + b_res = &mmio; > + } else { > + continue; > + } > + > + /* Size aligned to bridge window */ > + align = pci_resource_alignment(bridge, b_res); > + dev_sz = ALIGN(resource_size(dev_res), align); > + > + pci_dbg(dev, "%pR aligned to %llx\n", dev_res, %#llx to avoid confusion and match other output. > + (unsigned long long)dev_sz); > + > + if (dev_sz >= resource_size(b_res)) > + memset(b_res, 0, sizeof(*b_res)); > + else > + b_res->end -= dev_sz; > + > + pci_dbg(bridge, "updated available to %pR\n", b_res); > + } > + } > + > + pci_bus_distribute_available_resources(bridge->subordinate, > + add_list, io, mmio, > + mmio_pref); > return; > } > > -- > 2.35.1 >
