On Thu, Mar 04, 2021 at 09:42:44AM -0500, Prarit Bhargava wrote: > > > On 2/18/21 2:06 PM, Bjorn Helgaas wrote: > > On Thu, Feb 18, 2021 at 01:36:35PM -0500, Prarit Bhargava wrote: > >> On 1/26/21 10:12 AM, Bjorn Helgaas wrote: > >>> On Tue, Jan 26, 2021 at 09:05:23AM -0500, Prarit Bhargava wrote: > >>>> On 1/26/21 8:53 AM, Leon Romanovsky wrote: > >>>>> On Tue, Jan 26, 2021 at 08:42:12AM -0500, Prarit Bhargava wrote: > >>>>>> On 1/26/21 8:14 AM, Leon Romanovsky wrote: > >>>>>>> On Tue, Jan 26, 2021 at 07:54:46AM -0500, Prarit Bhargava wrote: > >>>>>>>> Leon Romanovsky <leon@xxxxxxxxxx> wrote: > >>>>>>>>> On Mon, Jan 25, 2021 at 02:41:38PM -0500, Prarit Bhargava wrote: > >>>>>>>>>> There are two situations where driver load messages are helpful. > >>>>>>>>>> > >>>>>>>>>> 1) Some drivers silently load on devices and debugging driver or system > >>>>>>>>>> failures in these cases is difficult. While some drivers (networking > >>>>>>>>>> for example) may not completely initialize when the PCI driver probe() function > >>>>>>>>>> has returned, it is still useful to have some idea of driver completion. > >>>>>>>>> > >>>>>>>>> Sorry, probably it is me, but I don't understand this use case. > >>>>>>>>> Are you adding global to whole kernel command line boot argument to debug > >>>>>>>>> what and when? > >>>>>>>>> > >>>>>>>>> During boot: > >>>>>>>>> If device success, you will see it in /sys/bus/pci/[drivers|devices]/*. > >>>>>>>>> If device fails, you should get an error from that device (fix the > >>>>>>>>> device to return an error), or something immediately won't work and > >>>>>>>>> you won't see it in sysfs. > >>>>>>>> > >>>>>>>> What if there is a panic during boot? There's no way to get to sysfs. > >>>>>>>> That's the case where this is helpful. > >>>>>>> > >>>>>>> How? If you have kernel panic, it means you have much more worse problem > >>>>>>> than not-supported device. If kernel panic was caused by the driver, you > >>>>>>> will see call trace related to it. If kernel panic was caused by > >>>>>>> something else, supported/not supported won't help here. > >>>>>> > >>>>>> I still have no idea *WHICH* device it was that the panic occurred on. > >>>>> > >>>>> The kernel panic is printed from the driver. There is one driver loaded > >>>>> for all same PCI devices which are probed without relation to their > >>>>> number.> > >>>>> If you have host with ten same cards, you will see one driver and this > >>>>> is where the problem and not in supported/not-supported device. > >>>> > >>>> That's true, but you can also have different cards loading the same driver. > >>>> See, for example, any PCI_IDs list in a driver. > >>>> > >>>> For example, > >>>> > >>>> 10:00.0 RAID bus controller: Broadcom / LSI MegaRAID SAS-3 3008 [Fury] (rev 02) > >>>> 20:00.0 RAID bus controller: Broadcom / LSI MegaRAID SAS-3 3108 [Invader] (rev 02) > >>>> > >>>> Both load the megaraid driver and have different profiles within the > >>>> driver. I have no idea which one actually panicked until removing > >>>> one card. > >>>> > >>>> It's MUCH worse when debugging new hardware and getting a panic > >>>> from, for example, the uncore code which binds to a PCI mapped > >>>> device. One device might work and the next one doesn't. And > >>>> then you can multiply that by seeing *many* panics at once and > >>>> trying to determine if the problem was on one specific socket, > >>>> die, or core. > >>> > >>> Would a dev_panic() interface that identified the device and > >>> driver help with this? > >> > >> ^^ the more I look at this problem, the more a dev_panic() that > >> would output a device specific message at panic time is what I > >> really need. > > I went down this road a bit and had a realization. The issue isn't > with printing something at panic time, but the *data* that is > output. Each PCI device is associated with a struct device. That > device struct's name is output for dev_dbg(), etc., commands. The > PCI subsystem sets the device struct name at drivers/pci/probe.c: > 1799 > > dev_set_name(&dev->dev, "%04x:%02x:%02x.%d", pci_domain_nr(dev->bus), > dev->bus->number, PCI_SLOT(dev->devfn), > PCI_FUNC(dev->devfn)); > > My problem really is that the above information is insufficient when > I (or a user) need to debug a system. The complexities of debugging > multiple broken driver loads would be much easier if I didn't have > to constantly add this output manually :). This *should* already be in the dmesg log: pci 0000:00:00.0: [8086:5910] type 00 class 0x060000 pci 0000:00:01.0: [8086:1901] type 01 class 0x060400 pci 0000:00:02.0: [8086:591b] type 00 class 0x030000 So if you had a dev_panic(), that message would include the bus/device/function number, and that would be enough to find the vendor/device ID from when the device was first enumerated. Or are you saying you can't get the part of the dmesg log that contains those vendor/device IDs? > Would you be okay with adding a *debug* parameter to expand the > device name to include the vendor & device ID pair? FWIW, I'm > somewhat against yet-another-kernel-option but that's really the > information I need. I could then add dev_dbg() statements in the > local_pci_probe() function.
