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.
> >
> > josh
> > _______________________________________________
> > kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx
> > To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx
Thanks
Dave
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