linux-kernel - Re: [PATCH V4 6/6] x86/Hyper-V: Report crash data in die() when panic_on

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Date:   Tue, 31 Mar 2020 22:26:06 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Michael Kelley <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <liuwe@...rosoft.com>
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        vkuznets <vkuznets@...hat.com>
Subject: Re: [PATCH V4 6/6] x86/Hyper-V: Report crash data in die() when
 panic_on_oops is set



On 3/31/2020 9:51 PM, Michael Kelley wrote:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com> 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@...rosoft.com>
>> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>> ---
>> 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
>