Re: [PATCH V4 6/6] x86/Hyper-V: Report crash data in die() when panic_on_oops is set

[Tianyu Lan]

On 3/31/2020 9:51 PM, Michael Kelley wrote:
> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> Sent: Tuesday, March 31, 2020 12:39 AM
> > When oops happens with panic_on_oops unset, the oops
> > thread is killed by die() and system continues to run.
> > In such case, guest should not report crash register
> > data to host since system still runs. Fix it.
> >
> > Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> > Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> > ---
> > Change since v3:
> > 	Fix compile error
> > ---
> >   drivers/hv/vmbus_drv.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> > index 172ceae69abb..4bc02aea2098 100644
> > --- a/drivers/hv/vmbus_drv.c
> > +++ b/drivers/hv/vmbus_drv.c
> > @@ -31,6 +31,7 @@
> >   #include <linux/kdebug.h>
> >   #include <linux/efi.h>
> >   #include <linux/random.h>
> > +#include <linux/kernel.h>
>
> Unfortunately, adding the #include doesn't solve the problem.  The error occurs when
> CONFIG_HYPERV=m, because panic_on_oops is not exported.  I haven't thought it
> through, but hopefully there's a solution where panic_on_oops can be tested in
> hyperv_report_panic() or some other Hyper-V specific function that's never in a
> module, so that we don't need to export panic_on_oops.

Yes, I don't consider modules case. I think we may introduce a check 
function of panic_on_oops in the mshyperv.c and expose it to module.

> Michael
>
> >   #include <linux/syscore_ops.h>
> >   #include <clocksource/hyperv_timer.h>
> >   #include "hyperv_vmbus.h"
> > @@ -91,7 +92,7 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long
> > val,
> >   	 * doing hyperv_report_panic_msg() later with kmsg data, don't do
> >   	 * the notification here.
> >   	 */
> > -	if (hyperv_report_reg())
> > +	if (hyperv_report_reg() && panic_on_oops)
> >   		hyperv_report_panic(regs, val);
> >   	return NOTIFY_DONE;
> >   }
> > --
> > 2.14.5