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!
> 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
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;
}
