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.
cheers
> diff --git a/arch/powerpc/platforms/pseries/ras.c
> b/arch/powerpc/platforms/pseries/ras.c
> index 149cec2212e6..f57ca0c570be 100644
> --- a/arch/powerpc/platforms/pseries/ras.c
> +++ b/arch/powerpc/platforms/pseries/ras.c
> @@ -719,6 +719,7 @@ static int mce_handle_err_virtmode(struct pt_regs *regs,
>
> static int mce_handle_error(struct pt_regs *regs, struct rtas_error_log
> *errp)
> {
> + unsigned long msr;
> struct pseries_errorlog *pseries_log;
> struct pseries_mc_errorlog *mce_log = NULL;
> int disposition = rtas_error_disposition(errp);
> @@ -747,9 +748,12 @@ 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);
> + mtmsr(msr);
> +
> return disposition;
> }
>
