powerpc/powernv/mce: Don't silently restart the machine

powerpc/powernv/mce: Don't silently restart the machine

[Balbir Singh]

On MCE the current code will restart the machine with
ppc_md.restart(). This case was extremely unlikely since
prior to that a skiboot call is made and that resulted in
a checkstop for analysis.

With newer skiboots, on P9 we don't checkstop the box by
default, instead we return back to the kernel to extract
useful information at the time of the MCE. While we still
get this information, this patch converts the restart to
a panic(), so that if configured a dump can be taken and
we can track and probably debug the potential issue causing
the MCE.

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/platforms/powernv/opal.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 69b5263fc9e3..b510a6f41b00 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -500,9 +500,12 @@ void pnv_platform_error_reboot(struct pt_regs *regs, const char *msg)
 	 *    opal to trigger checkstop explicitly for error analysis.
 	 *    The FSP PRD component would have already got notified
 	 *    about this error through other channels.
+	 * 4. We are running on a newer skiboot that by default does
+	 *    not cause a checkstop, drops us back to the kernel to
+	 *    extract context and state at the time of the error.
 	 */
 
-	ppc_md.restart(NULL);
+	panic("PowerNV Unrecovered Machine Check");
 }
 
 int opal_machine_check(struct pt_regs *regs)
-- 
2.13.6

Re: powerpc/powernv/mce: Don't silently restart the machine

[Michael Ellerman]

Balbir Singh <bsingharora@gmail.com> writes:

> On MCE the current code will restart the machine with
> ppc_md.restart(). This case was extremely unlikely since
> prior to that a skiboot call is made and that resulted in
> a checkstop for analysis.
>
> With newer skiboots, on P9 we don't checkstop the box by
> default, instead we return back to the kernel to extract
> useful information at the time of the MCE. While we still
> get this information, this patch converts the restart to
> a panic(), so that if configured a dump can be taken and
> we can track and probably debug the potential issue causing
> the MCE.
>
> Signed-off-by: Balbir Singh <bsingharora@gmail.com>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  arch/powerpc/platforms/powernv/opal.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index 69b5263fc9e3..b510a6f41b00 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -500,9 +500,12 @@ void pnv_platform_error_reboot(struct pt_regs *regs, const char *msg)
                                                                            ^^^^^^^^^^^^^^^
Why don't we use the msg ..

>  	 *    opal to trigger checkstop explicitly for error analysis.
>  	 *    The FSP PRD component would have already got notified
>  	 *    about this error through other channels.
> +	 * 4. We are running on a newer skiboot that by default does
> +	 *    not cause a checkstop, drops us back to the kernel to
> +	 *    extract context and state at the time of the error.
>  	 */
>  
> -	ppc_md.restart(NULL);
> +	panic("PowerNV Unrecovered Machine Check");
              ^
              Here.

Because we can get here from a HMI so it's confusing to print "Machine
Check" in that case, and we have the msg already.

So just:

> +	panic(msg);

cheers

Re: powerpc/powernv/mce: Don't silently restart the machine

[Balbir Singh]

On Wed, Feb 28, 2018 at 8:49 PM, Michael Ellerman <mpe@ellerman.id.au> wrote:
> Balbir Singh <bsingharora@gmail.com> writes:
>
>> On MCE the current code will restart the machine with
>> ppc_md.restart(). This case was extremely unlikely since
>> prior to that a skiboot call is made and that resulted in
>> a checkstop for analysis.
>>
>> With newer skiboots, on P9 we don't checkstop the box by
>> default, instead we return back to the kernel to extract
>> useful information at the time of the MCE. While we still
>> get this information, this patch converts the restart to
>> a panic(), so that if configured a dump can be taken and
>> we can track and probably debug the potential issue causing
>> the MCE.
>>
>> Signed-off-by: Balbir Singh <bsingharora@gmail.com>
>> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>> ---
>>  arch/powerpc/platforms/powernv/opal.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
>> index 69b5263fc9e3..b510a6f41b00 100644
>> --- a/arch/powerpc/platforms/powernv/opal.c
>> +++ b/arch/powerpc/platforms/powernv/opal.c
>> @@ -500,9 +500,12 @@ void pnv_platform_error_reboot(struct pt_regs *regs, const char *msg)
>                                                                             ^^^^^^^^^^^^^^^
> Why don't we use the msg ..
>
>>        *    opal to trigger checkstop explicitly for error analysis.
>>        *    The FSP PRD component would have already got notified
>>        *    about this error through other channels.
>> +      * 4. We are running on a newer skiboot that by default does
>> +      *    not cause a checkstop, drops us back to the kernel to
>> +      *    extract context and state at the time of the error.
>>        */
>>
>> -     ppc_md.restart(NULL);
>> +     panic("PowerNV Unrecovered Machine Check");
>               ^
>               Here.
>
> Because we can get here from a HMI so it's confusing to print "Machine
> Check" in that case, and we have the msg already.
>
> So just:
>
>> +     panic(msg);
>

My bad, we used to have two of these one in opal and opal-hmi and the
diff from the previous change showed this message. Resending

Thanks,
Balbir

Re: powerpc/powernv/mce: Don't silently restart the machine

[Michael Ellerman]

On Thu, 2018-03-08 at 00:36:06 UTC, Balbir Singh wrote:
> On MCE the current code will restart the machine with
> ppc_md.restart(). This case was extremely unlikely since
> prior to that a skiboot call is made and that resulted in
> a checkstop for analysis.
> 
> With newer skiboots, on P9 we don't checkstop the box by
> default, instead we return back to the kernel to extract
> useful information at the time of the MCE. While we still
> get this information, this patch converts the restart to
> a panic(), so that if configured a dump can be taken and
> we can track and probably debug the potential issue causing
> the MCE.
> 
> Signed-off-by: Balbir Singh <bsingharora@gmail.com>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> Reviewed-by: Stewart Smith <stewart@linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/5ee573e8ef034e687c420cb1091137

cheers