On 08/07/2018 10:24 PM, Michal Suchánek wrote:
> Hello,
>
>
> On Tue, 07 Aug 2018 19:47:14 +0530
> "Mahesh J Salgaonkar" <mah...@linux.vnet.ibm.com> wrote:
>
>> From: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com>
>>
>> On pseries, as of today system crashes if we get a machine check
>> exceptions due to SLB errors. These are soft errors and can be fixed
>> by flushing the SLBs so the kernel can continue to function instead of
>> system crash. We do this in real mode before turning on MMU. Otherwise
>> we would run into nested machine checks. This patch now fetches the
>> rtas error log in real mode and flushes the SLBs on SLB errors.
>>
>> Signed-off-by: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com>
>> Signed-off-by: Michal Suchanek <msucha...@suse.com>
>> ---
>>
>> Changes in V7:
>> - Fold Michal's patch into this patch.
>> - Handle MSR_RI=0 and evil context case in MC handler.
>> ---
>> arch/powerpc/include/asm/book3s/64/mmu-hash.h | 1
>> arch/powerpc/include/asm/machdep.h | 1
>> arch/powerpc/kernel/exceptions-64s.S | 112
>> +++++++++++++++++++++++++
>> arch/powerpc/kernel/mce.c | 15 +++
>> arch/powerpc/mm/slb.c | 6 +
>> arch/powerpc/platforms/powernv/setup.c | 11 ++
>> arch/powerpc/platforms/pseries/pseries.h | 1
>> arch/powerpc/platforms/pseries/ras.c | 51 +++++++++++
>> arch/powerpc/platforms/pseries/setup.c | 1 9 files changed,
>> 195 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
>> b/arch/powerpc/include/asm/book3s/64/mmu-hash.h index
>> 50ed64fba4ae..cc00a7088cf3 100644 ---
>> a/arch/powerpc/include/asm/book3s/64/mmu-hash.h +++
>> b/arch/powerpc/include/asm/book3s/64/mmu-hash.h @@ -487,6 +487,7 @@
>> extern void hpte_init_native(void);
>> extern void slb_initialize(void);
>> extern void slb_flush_and_rebolt(void);
>> +extern void slb_flush_and_rebolt_realmode(void);
>>
>> extern void slb_vmalloc_update(void);
>> extern void slb_set_size(u16 size);
>> diff --git a/arch/powerpc/include/asm/machdep.h
>> b/arch/powerpc/include/asm/machdep.h index a47de82fb8e2..b4831f1338db
>> 100644 --- a/arch/powerpc/include/asm/machdep.h
>> +++ b/arch/powerpc/include/asm/machdep.h
>> @@ -108,6 +108,7 @@ struct machdep_calls {
>>
>> /* Early exception handlers called in realmode */
>> int (*hmi_exception_early)(struct pt_regs
>> *regs);
>> + long (*machine_check_early)(struct pt_regs
>> *regs);
>> /* Called during machine check exception to retrive fixup
>> address. */ bool (*mce_check_early_recovery)(struct
>> pt_regs *regs); diff --git a/arch/powerpc/kernel/exceptions-64s.S
>> b/arch/powerpc/kernel/exceptions-64s.S index
>> 285c6465324a..cb06f219570a 100644 ---
>> a/arch/powerpc/kernel/exceptions-64s.S +++
>> b/arch/powerpc/kernel/exceptions-64s.S @@ -332,6 +332,9 @@
>> TRAMP_REAL_BEGIN(machine_check_pSeries) machine_check_fwnmi:
>> SET_SCRATCH0(r13) /* save r13 */
>> EXCEPTION_PROLOG_0(PACA_EXMC)
>> +BEGIN_FTR_SECTION
>> + b machine_check_pSeries_early
>> +END_FTR_SECTION_IFCLR(CPU_FTR_HVMODE)
>> machine_check_pSeries_0:
>> EXCEPTION_PROLOG_1(PACA_EXMC, KVMTEST_PR, 0x200)
>> /*
>> @@ -343,6 +346,90 @@ machine_check_pSeries_0:
>>
>> TRAMP_KVM_SKIP(PACA_EXMC, 0x200)
>>
>> +TRAMP_REAL_BEGIN(machine_check_pSeries_early)
>> +BEGIN_FTR_SECTION
>> + EXCEPTION_PROLOG_1(PACA_EXMC, NOTEST, 0x200)
>> + mr r10,r1 /* Save r1 */
>> + ld r1,PACAMCEMERGSP(r13) /* Use MC emergency
>> stack */
>> + subi r1,r1,INT_FRAME_SIZE /* alloc stack
>> frame */
>> + mfspr r11,SPRN_SRR0 /* Save SRR0 */
>> + mfspr r12,SPRN_SRR1 /* Save SRR1 */
>> + EXCEPTION_PROLOG_COMMON_1()
>> + EXCEPTION_PROLOG_COMMON_2(PACA_EXMC)
>> + EXCEPTION_PROLOG_COMMON_3(0x200)
>> + addi r3,r1,STACK_FRAME_OVERHEAD
>> + BRANCH_LINK_TO_FAR(machine_check_early) /* Function call ABI
>> */
>> + ld r12,_MSR(r1)
>> + andi. r11,r12,MSR_PR /* See if coming
>> from user. */
>> + bne 2f /* continue in V mode
>> if we are. */ +
>> + /*
>> + * At this point we are not sure about what context we come
>> from.
>> + * We may be in the middle of swithing stack. r1 may not be
>> valid.
>> + * Hence stay on emergency stack, call
>> machine_check_exception and
>> + * return from the interrupt.
>> + * But before that, check if this is an un-recoverable
>> exception.
>> + * If yes, then stay on emergency stack and panic.
>> + */
>> + andi. r11,r12,MSR_RI
>> + bne 1f
>> +
>> + /*
>> + * Check if we have successfully handled/recovered from
>> error, if not
>> + * then stay on emergency stack and panic.
>> + */
>> + cmpdi r3,0 /* see if we handled MCE
>> successfully */
>> + bne 1f /* if handled then return from
>> interrupt */ +
>> + LOAD_HANDLER(r10,unrecover_mce)
>> + mtspr SPRN_SRR0,r10
>> + ld r10,PACAKMSR(r13)
>> + /*
>> + * We are going down. But there are chances that we might
>> get hit by
>> + * another MCE during panic path and we may run into
>> unstable state
>> + * with no way out. Hence, turn ME bit off while going down,
>> so that
>> + * when another MCE is hit during panic path, hypervisor will
>> + * power cycle the lpar, instead of getting into MCE loop.
>> + */
>> + li r3,MSR_ME
>> + andc r10,r10,r3 /* Turn off MSR_ME */
>> + mtspr SPRN_SRR1,r10
>> + RFI_TO_KERNEL
>> + b .
>> +
>> + /* Stay on emergency stack and return from interrupt. */
>> +1: LOAD_HANDLER(r10,mce_return)
>> + mtspr SPRN_SRR0,r10
>> + ld r10,PACAKMSR(r13)
>> + mtspr SPRN_SRR1,r10
>> + RFI_TO_KERNEL
>> + b .
>
> I think that the logic should be inverted here. That is we should check
> for unrecoverable and unhandled exceptions and jump to unrecov_mce if
> found, fallthrough to mce_return otherwise.
sure. will make that change in next revision.
Thanks,
-Mahesh.
>
> Thanks
>
> Michal
>
>
>> +
>> + /* Move original SRR0 and SRR1 into the respective regs */
>> +2: ld r9,_MSR(r1)
>> + mtspr SPRN_SRR1,r9
>> + ld r3,_NIP(r1)
>> + mtspr SPRN_SRR0,r3
>> + ld r9,_CTR(r1)
>> + mtctr r9
>> + ld r9,_XER(r1)
>> + mtxer r9
>> + ld r9,_LINK(r1)
>> + mtlr r9
>> + REST_GPR(0, r1)
>> + REST_8GPRS(2, r1)
>> + REST_GPR(10, r1)
>> + ld r11,_CCR(r1)
>> + mtcr r11
>> + REST_GPR(11, r1)
>> + REST_2GPRS(12, r1)
>> + /* restore original r1. */
>> + ld r1,GPR1(r1)
>> + SET_SCRATCH0(r13) /* save r13 */
>> + EXCEPTION_PROLOG_0(PACA_EXMC)
>> + b machine_check_pSeries_0
>> +END_FTR_SECTION_IFCLR(CPU_FTR_HVMODE)
>> +
>> EXC_COMMON_BEGIN(machine_check_common)
>> /*
>> * Machine check is different because we use a different
>> @@ -536,6 +623,31 @@ EXC_COMMON_BEGIN(unrecover_mce)
>> bl unrecoverable_exception
>> b 1b
>>
>> +EXC_COMMON_BEGIN(mce_return)
>> + /* Invoke machine_check_exception to print MCE event and
>> return. */
>> + addi r3,r1,STACK_FRAME_OVERHEAD
>> + bl machine_check_exception
>> + ld r9,_MSR(r1)
>> + mtspr SPRN_SRR1,r9
>> + ld r3,_NIP(r1)
>> + mtspr SPRN_SRR0,r3
>> + ld r9,_CTR(r1)
>> + mtctr r9
>> + ld r9,_XER(r1)
>> + mtxer r9
>> + ld r9,_LINK(r1)
>> + mtlr r9
>> + REST_GPR(0, r1)
>> + REST_8GPRS(2, r1)
>> + REST_GPR(10, r1)
>> + ld r11,_CCR(r1)
>> + mtcr r11
>> + REST_GPR(11, r1)
>> + REST_2GPRS(12, r1)
>> + /* restore original r1. */
>> + ld r1,GPR1(r1)
>> + RFI_TO_KERNEL
>> + b .
>>
>> EXC_REAL(data_access, 0x300, 0x80)
>> EXC_VIRT(data_access, 0x4300, 0x80, 0x300)
>> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
>> index efdd16a79075..ae17d8aa60c4 100644
>> --- a/arch/powerpc/kernel/mce.c
>> +++ b/arch/powerpc/kernel/mce.c
>> @@ -488,10 +488,19 @@ long machine_check_early(struct pt_regs *regs)
>> {
>> long handled = 0;
>>
>> - __this_cpu_inc(irq_stat.mce_exceptions);
>> + /*
>> + * For pSeries we count mce when we go into virtual mode
>> machine
>> + * check handler. Hence skip it. Also, We can't access per
>> cpu
>> + * variables in real mode for LPAR.
>> + */
>> + if (early_cpu_has_feature(CPU_FTR_HVMODE))
>> + __this_cpu_inc(irq_stat.mce_exceptions);
>>
>> - if (cur_cpu_spec && cur_cpu_spec->machine_check_early)
>> - handled = cur_cpu_spec->machine_check_early(regs);
>> + /*
>> + * See if platform is capable of handling machine check.
>> + */
>> + if (ppc_md.machine_check_early)
>> + handled = ppc_md.machine_check_early(regs);
>> return handled;
>> }
>>
>> diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
>> index cb796724a6fc..e89f675f1b5e 100644
>> --- a/arch/powerpc/mm/slb.c
>> +++ b/arch/powerpc/mm/slb.c
>> @@ -145,6 +145,12 @@ void slb_flush_and_rebolt(void)
>> get_paca()->slb_cache_ptr = 0;
>> }
>>
>> +void slb_flush_and_rebolt_realmode(void)
>> +{
>> + __slb_flush_and_rebolt();
>> + get_paca()->slb_cache_ptr = 0;
>> +}
>> +
>> void slb_vmalloc_update(void)
>> {
>> unsigned long vflags;
>> diff --git a/arch/powerpc/platforms/powernv/setup.c
>> b/arch/powerpc/platforms/powernv/setup.c index
>> f96df0a25d05..b74c93bc2e55 100644 ---
>> a/arch/powerpc/platforms/powernv/setup.c +++
>> b/arch/powerpc/platforms/powernv/setup.c @@ -431,6 +431,16 @@ static
>> unsigned long pnv_get_proc_freq(unsigned int cpu) return ret_freq;
>> }
>>
>> +static long pnv_machine_check_early(struct pt_regs *regs)
>> +{
>> + long handled = 0;
>> +
>> + if (cur_cpu_spec && cur_cpu_spec->machine_check_early)
>> + handled = cur_cpu_spec->machine_check_early(regs);
>> +
>> + return handled;
>> +}
>> +
>> define_machine(powernv) {
>> .name = "PowerNV",
>> .probe = pnv_probe,
>> @@ -442,6 +452,7 @@ define_machine(powernv) {
>> .machine_shutdown = pnv_shutdown,
>> .power_save = NULL,
>> .calibrate_decr = generic_calibrate_decr,
>> + .machine_check_early = pnv_machine_check_early,
>> #ifdef CONFIG_KEXEC_CORE
>> .kexec_cpu_down = pnv_kexec_cpu_down,
>> #endif
>> diff --git a/arch/powerpc/platforms/pseries/pseries.h
>> b/arch/powerpc/platforms/pseries/pseries.h index
>> 60db2ee511fb..ec2a5f61d4a4 100644 ---
>> a/arch/powerpc/platforms/pseries/pseries.h +++
>> b/arch/powerpc/platforms/pseries/pseries.h @@ -24,6 +24,7 @@ struct
>> pt_regs;
>> extern int pSeries_system_reset_exception(struct pt_regs *regs);
>> extern int pSeries_machine_check_exception(struct pt_regs *regs);
>> +extern long pSeries_machine_check_realmode(struct pt_regs *regs);
>>
>> #ifdef CONFIG_SMP
>> extern void smp_init_pseries(void);
>> diff --git a/arch/powerpc/platforms/pseries/ras.c
>> b/arch/powerpc/platforms/pseries/ras.c index
>> 851ce326874a..e4420f7c8fda 100644 ---
>> a/arch/powerpc/platforms/pseries/ras.c +++
>> b/arch/powerpc/platforms/pseries/ras.c @@ -427,6 +427,35 @@ int
>> pSeries_system_reset_exception(struct pt_regs *regs) return 0; /*
>> need to perform reset */ }
>>
>> +static int mce_handle_error(struct rtas_error_log *errp)
>> +{
>> + struct pseries_errorlog *pseries_log;
>> + struct pseries_mc_errorlog *mce_log;
>> + int disposition = rtas_error_disposition(errp);
>> + uint8_t error_type;
>> +
>> + if (!rtas_error_extended(errp))
>> + goto out;
>> +
>> + pseries_log = get_pseries_errorlog(errp,
>> PSERIES_ELOG_SECT_ID_MCE);
>> + if (pseries_log == NULL)
>> + goto out;
>> +
>> + mce_log = (struct pseries_mc_errorlog *)pseries_log->data;
>> + error_type = rtas_mc_error_type(mce_log);
>> +
>> + if ((disposition == RTAS_DISP_NOT_RECOVERED) &&
>> + (error_type == PSERIES_MC_ERROR_TYPE_SLB)) {
>> + /* Store the old slb content someplace. */
>> + slb_flush_and_rebolt_realmode();
>> + disposition = RTAS_DISP_FULLY_RECOVERED;
>> + rtas_set_disposition_recovered(errp);
>> + }
>> +
>> +out:
>> + return disposition;
>> +}
>> +
>> /*
>> * Process MCE rtas errlog event.
>> */
>> @@ -503,11 +532,31 @@ int pSeries_machine_check_exception(struct
>> pt_regs *regs) struct rtas_error_log *errp;
>>
>> if (fwnmi_active) {
>> - errp = fwnmi_get_errinfo(regs);
>> fwnmi_release_errinfo();
>> + errp = fwnmi_get_errlog();
>> if (errp && recover_mce(regs, errp))
>> return 1;
>> }
>>
>> return 0;
>> }
>> +
>> +long pSeries_machine_check_realmode(struct pt_regs *regs)
>> +{
>> + struct rtas_error_log *errp;
>> + int disposition;
>> +
>> + if (fwnmi_active) {
>> + errp = fwnmi_get_errinfo(regs);
>> + /*
>> + * Call to fwnmi_release_errinfo() in real mode
>> causes kernel
>> + * to panic. Hence we will call it as soon as we go
>> into
>> + * virtual mode.
>> + */
>> + disposition = mce_handle_error(errp);
>> + if (disposition == RTAS_DISP_FULLY_RECOVERED)
>> + return 1;
>> + }
>> +
>> + return 0;
>> +}
>> diff --git a/arch/powerpc/platforms/pseries/setup.c
>> b/arch/powerpc/platforms/pseries/setup.c index
>> b42087cd8c6b..7a9421d089d8 100644 ---
>> a/arch/powerpc/platforms/pseries/setup.c +++
>> b/arch/powerpc/platforms/pseries/setup.c @@ -1000,6 +1000,7 @@
>> define_machine(pseries) { .calibrate_decr =
>> generic_calibrate_decr, .progress = rtas_progress,
>> .system_reset_exception = pSeries_system_reset_exception,
>> + .machine_check_early = pSeries_machine_check_realmode,
>> .machine_check_exception = pSeries_machine_check_exception,
>> #ifdef CONFIG_KEXEC_CORE
>> .machine_kexec = pSeries_machine_kexec,
>>
>>
>
