On Friday, March 03/02/18, 2018 at 18:52:45 +0530, Eric W. Biederman wrote: > Rahul Lakkireddy <rahul.lakkireddy@xxxxxxxxxxx> writes: > > > On production servers running variety of workloads over time, kernel > > panic can happen sporadically after days or even months. It is > > important to collect as much debug logs as possible to root cause > > and fix the problem, that may not be easy to reproduce. Snapshot of > > underlying hardware/firmware state (like register dump, firmware > > logs, adapter memory, etc.), at the time of kernel panic will be very > > helpful while debugging the culprit device driver. > > > > This series of patches add new generic framework that enable device > > drivers to collect device specific snapshot of the hardware/firmware > > state of the underlying device at the time of kernel panic. The > > collected logs are appended to vmcore along with details, such as > > start address and length of the logs, which are required for > > extraction during post-analysis. > > > > Device drivers can use crash_driver_dump_register() to register their > > callback that collects underlying device specific hardware/firmware > > logs during kernel panic (i.e. before booting into the second kernel). > > Drivers can unregister with crash_driver_dump_unregister(). > > > > To extract the device specific hardware/firmware logs using crash: > > > > crash> help -D | grep DRIVERDUMP > > DRIVERDUMP=(cxgb4_0000:02:00.4, ffffb131090bd000, 37782968) > > > > crash> rd ffffb131090bd000 37782968 -r hardware.log > > 37782968 bytes copied from 0xffffb131090bd000 to hardware.log > > > > Patch 1 adds API to allow drivers to register callback to > > collect the device specific hardware/firmware logs. > > > > Patch 2 shows a cxgb4 driver example using the API to collect > > hardware/firmware logs during kernel panic. > > > > Suggestions and feedback will be much appreciated. > > I strongly suggest you figure out how to run this code in the > crash recovery kernel before your hardware is initialized. > That will give you a known good kernel to perform your collection from. > > Every line of code we add to the kexec on panic code path tends to add > to it's fragility and increase the chance you won't get any information > at all. > > When the assumption is it is something wrong with your driver/hardware > that caused the crash, calling into your driver is a very bad idea. > Especially running code that does callbacks and all kinds of other cute > things. > > Doing this as the crash recover kernel boots up before much if any > hardware is initialized seems like a fine thing to do, and just > needs a little coordination with userspace to ensure the information > gets saved when a vmcore is computed. > Thanks for the feedback and suggestions. I will work on achieving this from the crash recover kernel. Thanks, Rahul _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
