On 2019/10/23 5:04, Bjorn Helgaas wrote: > On Sat, Oct 19, 2019 at 02:45:43PM +0800, Yunsheng Lin wrote: >> As the disscusion in [1]: > > We need to justify this patch right here in the commit log, not with a > pointer to a 50+ message email thread.
Ok, thanks. > >> A PCI device really _MUST_ have a node assigned. > > No, it's not really essential. It's *nice* if we know the node > closest to a PCI device, but the system should function correctly even > if we don't. The only problem is that it will be slower. Ok, will try to mention the info you mention here in the commit log. > > I think the underlying problem you're addressing is that: > > - NUMA_NO_NODE == -1, > - dev_to_node(dev) may return NUMA_NO_NODE, > - kmalloc(dev) relies on cpumask_of_node(dev_to_node(dev)), and > - cpumask_of_node(NUMA_NO_NODE) makes an invalid array reference > > For example, on arm64, mips loongson, s390, and x86, > cpumask_of_node(node) returns "node_to_cpumask_map[node]", and -1 is > an invalid array index. The invalid array index of -1 is the underlying problem here when cpumask_of_node(dev_to_node(dev)) is called and cpumask_of_node() is not NUMA_NO_NODE aware yet. In the "numa: make node_to_cpumask_map() NUMA_NO_NODE aware" thread disscusion, it is requested that it is better to warn about the pcie device without a node assigned by the firmware before making the cpumask_of_node() NUMA_NO_NODE aware, so that the system with pci devices of "NUMA_NO_NODE" node can be fixed by their vendor. See: https://lore.kernel.org/lkml/20191011111539.gx2...@hirez.programming.kicks-ass.net/ > > That problem can't be solved by emitting a warning, of course. I > assume some variation of your "numa: make node_to_cpumask_map() > NUMA_NO_NODE aware" patch [a] will solve that problem. > > [a] > https://lore.kernel.org/linux-mips/1568535656-158979-1-git-send-email-linyunsh...@huawei.com/T/#u > > It is probably a good idea to emit a warning about the performance > issue. > > When I run your patch on qemu, I see this: > > ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) > acpi PNP0A08:00: _OSC: OS supports [ExtendedConfig ASPM ClockPM Segments > MSI HPX-Type3] > acpi PNP0A08:00: _OSC: platform does not support [LTR] > acpi PNP0A08:00: _OSC: OS now controls [PME AER PCIeCapability] > PCI host bridge to bus 0000:00 > pci_bus 0000:00: root bus resource [io 0x0000-0x0cf7 window] > pci_bus 0000:00: root bus resource [io 0x0d00-0xffff window] > pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window] > pci_bus 0000:00: root bus resource [mem 0xc0000000-0xfebfffff window] > pci_bus 0000:00: root bus resource [mem 0x100000000-0x8ffffffff window] > pci_bus 0000:00: root bus resource [bus 00-ff] > pci0000:00: [Firmware Bug]: No node assigned on NUMA capable HW by BIOS. > Please contact your vendor for updates. > > I didn't debug it to see what's wrong with the " pci0000:00" string. > Ideally it would be connected with "acpi PNP0A08:00" since that's the > place where BIOS would make a fix but I suppose "pci_bus 0000:00" > would be adequate. It seems the string at the beginning of dev_err() output is consisted of dev_driver_string() and dev_name(). drivers/base/core.c: const char *dev_driver_string(const struct device *dev) { struct device_driver *drv; /* dev->driver can change to NULL underneath us because of unbinding, * so be careful about accessing it. dev->bus and dev->class should * never change once they are set, so they don't need special care. */ drv = READ_ONCE(dev->driver); return drv ? drv->name : (dev->bus ? dev->bus->name : (dev->class ? dev->class->name : "")); } The bridge device does not have a driver, a bus or a class, so dev_driver_string() will return "", that is why there is a extral space at the beginning of the " pci0000:00". I am not familiar with the pci, so not sure if this is a problem that the bridge device does not have a driver, a bus or a class. And the bus device has a class of pcibus_class, and name of pcibus_class is "pci_bus". So maybe change the warning to below: if (nr_node_ids > 1 && pcibus_to_node(bus) == NUMA_NO_NODE) dev_err(&bus->dev, FW_BUG "No node assigned on NUMA capable HW. Please contact your vendor for updates.\n"); And it seems a pci device's parent will always set to the bridge device in pci_setup_device(), and device_add() which will set the node to its parent's when the child device' node is NUMA_NO_NODE, maybe we can add the bridge device' node checking to make sure the pci device really does not have a node assigned, as below: if (nr_node_ids > 1 && pcibus_to_node(bus) == NUMA_NO_NODE && dev_to_node(bus->bridge) == NUMA_NO_NODE) dev_err(&bus->dev, FW_BUG "No node assigned on NUMA capable HW. Please contact your vendor for updates.\n"); > >> It is possible to >> have a PCI bridge shared between two nodes, such that the PCI >> devices have equidistance. But the moment you scale this out, you >> either get devices that are 'local' to a package while having >> multiple packages, or if you maintain a single bridge in a big >> system, things become so slow it all doesn't matter anyway. >> Assigning a node (one of the shared) is, in the generic ase of >> multiple packages, the better solution over assigning all nodes. >> >> As pci_device_add() will assign the pci device' node according to >> the bus the device is on, which is decided by pcibus_to_node(). >> Currently different arch may implement the pcibus_to_node() based >> on bus->sysdata or bus device' node, which has the same node as >> the bridge device. >> >> And for devices behind another bridge case, the child bus device >> is setup with proper parent bus device and inherit its parent' >> sysdata in pci_alloc_child_bus(), so the pcie device under the >> child bus should have the same node as the parent bridge when >> device_add() is called, which will set the node to its parent's >> node when the child device' node is NUMA_NO_NODE. >> >> So this patch only warns about the case when a host bridge device >> is registered with a node of NO_NODE in pci_register_host_bridge(). >> And it only warns about that when there are more than one numa >> nodes in the system. > > >> [1] >> https://lore.kernel.org/lkml/1568724534-146242-1-git-send-email-linyunsh...@huawei.com/ >> >> Signed-off-by: Yunsheng Lin <linyunsh...@huawei.com> >> --- >> drivers/pci/probe.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c >> index 3d5271a..22be96a 100644 >> --- a/drivers/pci/probe.c >> +++ b/drivers/pci/probe.c >> @@ -927,6 +927,9 @@ static int pci_register_host_bridge(struct >> pci_host_bridge *bridge) >> list_add_tail(&bus->node, &pci_root_buses); >> up_write(&pci_bus_sem); >> >> + if (nr_node_ids > 1 && dev_to_node(bus->bridge) == NUMA_NO_NODE) >> + dev_err(bus->bridge, FW_BUG "No node assigned on NUMA capable >> HW by BIOS. Please contact your vendor for updates.\n"); >> + >> return 0; >> >> unregister: > > . >
