Hi Prarit, 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? For driver_load_messages, it doesn't seem necessarily PCI-specific. If we want a message like that, maybe it could be in driver_probe_device() or similar? There are already a few pr_debug() calls in that path. There are some enabled by initcall_debug that include the return value from the probe; would those be close to what you're looking for? Bjorn
