Re: [PATCH v7 39/42] powerpc: move NMI entry/exit code into wrapper
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2021-02-05 23:39:59
Nicholas Piggin [off-list ref] writes:
Excerpts from Michael Ellerman's message of February 4, 2021 8:15 pm:quoted
Nicholas Piggin [off-list ref] writes:quoted
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 <npiggin@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 pSeriespseries hash. Blast!
The worst kind.
quoted
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
quoted hunk ↗ jump to hunk
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; }