Messages in this thread | | | Subject | Re: [PATCH 2/2] powerpc/book3s: mce: Use add_taint_no_warn() in machine_check_early(). | From | Mahesh Jagannath Salgaonkar <> | Date | Mon, 17 Apr 2017 16:49:41 +0530 |
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On 04/17/2017 04:09 PM, Daniel Axtens wrote: > Hi Mahesh, > >> Fixes: 27ea2c420cad powerpc: Set the correct kernel taint on machine check errors. > > I notice this Fixes a commit I introduced. Please could you cc me when > you do this? I am likely to miss it otherwise, especially since I have > now left IBM.
Sure will do. :-)
> > Being cced allows me to provide an Ack or a review. And getting feedback > on my changes is very helpful in becoming a better programmer. > > In this case, as per Michael's comment, why don't we just move the > add_taint from machine_check_early to > machine_check_process_queued_event - the other side of the work queue.
Yes. That is what my plan is. Also, that is not the only place. add_taint() need to be called from machine_check_exception() as well. So it will be called from two places.
Thanks, -Mahesh.
> > The work queue system is supposed to provide us with a safe place to do > printing, etc., so it's an appropriate place. Also, we already do > machine_check_print_event_info there, and adding the taint doesn't need > to be done synchronously. > > Regards, > Daniel > > Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com> writes: > >> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> >> >> machine_check_early() gets called in real mode. The very first time when >> add_taint() is called, it prints a warning which ends up calling opal >> call (that uses OPAL_CALL wrapper) for writing it to console. If we get a >> very first machine check while we are in opal we are doomed. OPAL_CALL >> overwrites the PACASAVEDMSR in r13 and in this case when we are done with >> MCE handling the original opal call will use this new MSR on it's way >> back to opal_return. This usually leads unexpected behaviour or kernel >> to panic. Instead use the add_taint_no_warn() that does not call printk. >> >> This is broken with current FW level. We got lucky so far for not getting >> very first MCE hit while in OPAL. But easily reproducible on Mambo. >> This should go to stable as well alongwith patch 1/2. >> >> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> >> --- >> arch/powerpc/kernel/traps.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c >> index 62b587f..4a048dc 100644 >> --- a/arch/powerpc/kernel/traps.c >> +++ b/arch/powerpc/kernel/traps.c >> @@ -306,7 +306,7 @@ long machine_check_early(struct pt_regs *regs) >> >> __this_cpu_inc(irq_stat.mce_exceptions); >> >> - add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE); >> + add_taint_no_warn(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE); >> >> /* >> * See if platform is capable of handling machine check. (e.g. PowerNV >
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