On 01/17/18 at 09:31am, Dave Young wrote:
> Don, thanks for ccing me.
> On 01/16/18 at 07:47am, Don Zickus wrote:
> > (cc'ing Dae Young)
> >
> > On Tue, Jan 16, 2018 at 07:41:36AM -0500, Josh Boyer wrote:
> > > On Tue, Jan 9, 2018 at 1:51 PM, Maxim Burgerhout <maxim@xxxxxxxxx> wrote:
> > > > I'm getting kernel panics in a VM that functions as a hypervisor, the moment
> > > > I spin up the nested guest (on AMD ThreadRipper / Fedora 27). That is
> > > > annoying, of course, so I try to be a good citizen and file a bug.
> > > >
> > > > For some reason though, I cannot get the core dumped. I get a core fine with
> > > > sysrq, but not with this actual panic. I've followed [1] to set up kdump and
> > > > crash, but everytime I trigger the crash and see my VM reboot, I see an
> > > > empty /var/crash afterwards.
> > > >
> > > > As was able to get the vmcore written to /var/crash on in a RHEL7 guest, I'm
> > > > starting to suspect a bug, but I'm unsure.
>
> One thing need check is if kdump service started successfully before the
> crash, ie. check /sys/kernel/kexec_crash_loaded.
>
> If use self-build kernel, you can check to use below patch for testing:
>
> ---
> It is useful to print kdump kernel loaded status in dump_stack()
> especially when panic happens so that we can differenciate
> kdump kernel early hang and a normal panic in a bug report.
>
> Signed-off-by: Dave Young <dyoung@xxxxxxxxxx>
> ---
> kernel/printk/printk.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> --- linux-x86.orig/kernel/printk/printk.c
> +++ linux-x86/kernel/printk/printk.c
> @@ -48,6 +48,7 @@
> #include <linux/sched/clock.h>
> #include <linux/sched/debug.h>
> #include <linux/sched/task_stack.h>
> +#include <linux/kexec.h>
>
> #include <linux/uaccess.h>
> #include <asm/sections.h>
> @@ -3127,6 +3128,8 @@ void dump_stack_print_info(const char *l
> if (dump_stack_arch_desc_str[0] != '\0')
> printk("%sHardware name: %s\n",
> log_lvl, dump_stack_arch_desc_str);
> + if (kexec_crash_loaded())
> + printk("%skdump kernel loaded\n", log_lvl);
>
> print_worker_info(log_lvl, current);
> }
>
> > > >
> > > > Any pointers on how to debug this?
> > > >
> > > > [1] https://fedoraproject.org/wiki/How_to_use_kdump_to_debug_kernel_crashes
> > >
> > > Adding the Fedora kernel list.
> > >
> > > Kdump isn't automatically tested in Fedora and while it can work, it
> > > can often be broken as well. There might be someone on the kernel
> > > list that is more familiar with the current state of kdump support in
> > > Fedora, or alternative methods for getting the kernel backtrace.
>
> Yes, since Fedora kernel updates frequently, it is not a surprise that
> kdump does not work. But it is always good to report a bug against
> "kexec-tools" component or "kernel" -> "Kexec/kdump" Subcomponent.
Hmm, I noticed in bugzilla there is no such subcomponent for Fedora
if so the kdump bugs can be routed to "kexec-tools" so that we can
be aware about them.
>
> > >
> > > josh
> > > _______________________________________________
> > > kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx
> > > To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx
>
> Thanks
> Dave
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