Excerpts from Nicholas Piggin's message of February 6, 2021 12:46 pm:
> Excerpts from Michael Ellerman's message of February 6, 2021 9:38 am:
>> Nicholas Piggin <npig...@gmail.com> writes:
>>> Excerpts from Michael Ellerman's message of February 4, 2021 8:15 pm:
>>>> Nicholas Piggin <npig...@gmail.com> writes:
>>>>> This moves the common NMI entry and exit code into the interrupt handler
>>>>> wrappers.
>>>>>
>>>>> This changes the behaviour of soft-NMI (watchdog) and HMI interrupts, and
>>>>> also MCE interrupts on 64e, by adding missing parts of the NMI entry to
>>>>> them.
>>>>>
>>>>> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
>>>>> ---
>>>>> arch/powerpc/include/asm/interrupt.h | 28 ++++++++++++++++++++++
>>>>> arch/powerpc/kernel/mce.c | 11 ---------
>>>>> arch/powerpc/kernel/traps.c | 35 +++++-----------------------
>>>>> arch/powerpc/kernel/watchdog.c | 10 ++++----
>>>>> 4 files changed, 38 insertions(+), 46 deletions(-)
>>>>
>>>> This is unhappy when injecting SLB multi-hits:
>>>>
>>>> root@p86-2:~# echo PPC_SLB_MULTIHIT >
>>>> /sys/kernel/debug/provoke-crash/DIRECT
>>>> [ 312.496026][ T1344] kernel BUG at
>>>> arch/powerpc/include/asm/interrupt.h:152!
>>>> [ 312.496037][ T1344] Oops: Exception in kernel mode, sig: 5 [#1]
>>>> [ 312.496045][ T1344] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA
>>>> pSeries
>>>
>>> pseries hash. Blast!
>>
>> The worst kind.
>>
>>>> 147 static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs,
>>>> struct interrupt_nmi_state *state)
>>>> 148 {
>>>> 149 if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
>>>> 150 !firmware_has_feature(FW_FEATURE_LPAR) ||
>>>> 151 radix_enabled() || (mfmsr() & MSR_DR))
>>>> 152 nmi_exit();
>>>>
>>>>
>>>> So presumably it's:
>>>>
>>>> #define __nmi_exit() \
>>>> do { \
>>>> BUG_ON(!in_nmi()); \
>>>
>>> Yes that would be it, pseries machine check enables MMU half way through
>>> so only one side of this triggers.
>>>
>>> The MSR_DR check is supposed to catch the other NMIs that run with MMU
>>> on (perf, watchdog, etc). Suppose it could test TRAP(regs) explicitly
>>> although I wonder if we should also do this to keep things balanced
>>
>> Yeah I think I like that. I'll give it a test.
>
> The msr restore? Looking closer, pseries_machine_check_realmode may have
> expected mce_handle_error to enable the MMU, because irq_work_queue uses
> some per-cpu variables I think.
>
> So the code might have to be rearranged a bit more than the patch below.
Here is a patch, it should go anywhere before this patch. Seems to
work with some test MCE injection on pseries hash.
Thanks,
Nick
--
powerpc/pseries/mce: restore msr before returning from handler
The pseries real-mode machine check handler can enable the MMU, and
return from the handler with the MMU still enabled.
This works, but real-mode handler wrapper exit handlers want to rely
on the MMU being in real-mode. So change the pseries handler to
restore the MSR after it has finished virtual mode tasks.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/platforms/pseries/ras.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/ras.c
b/arch/powerpc/platforms/pseries/ras.c
index 2d9f985fd13a..377439e88598 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -722,6 +722,7 @@ static int mce_handle_error(struct pt_regs *regs, struct
rtas_error_log *errp)
struct pseries_errorlog *pseries_log;
struct pseries_mc_errorlog *mce_log = NULL;
int disposition = rtas_error_disposition(errp);
+ unsigned long msr;
u8 error_type;
if (!rtas_error_extended(errp))
@@ -747,9 +748,21 @@ static int mce_handle_error(struct pt_regs *regs, struct
rtas_error_log *errp)
* SLB multihit is done by now.
*/
out:
- mtmsr(mfmsr() | MSR_IR | MSR_DR);
+ msr = mfmsr();
+ mtmsr(msr | MSR_IR | MSR_DR);
+
disposition = mce_handle_err_virtmode(regs, errp, mce_log,
disposition);
+
+ /*
+ * Queue irq work to log this rtas event later.
+ * irq_work_queue uses per-cpu variables, so do this in virt
+ * mode as well.
+ */
+ irq_work_queue(&mce_errlog_process_work);
+
+ mtmsr(msr);
+
return disposition;
}
@@ -865,10 +878,8 @@ long pseries_machine_check_realmode(struct pt_regs *regs)
* virtual mode.
*/
disposition = mce_handle_error(regs, errp);
- fwnmi_release_errinfo();
- /* Queue irq work to log this rtas event later. */
- irq_work_queue(&mce_errlog_process_work);
+ fwnmi_release_errinfo();
if (disposition == RTAS_DISP_FULLY_RECOVERED)
return 1;
--
2.23.0
