On 08/01/2018 11:28 AM, Nicholas Piggin wrote:
> On Wed, 04 Jul 2018 23:28:21 +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>
>> ---
>> arch/powerpc/include/asm/book3s/64/mmu-hash.h | 1
>> arch/powerpc/include/asm/machdep.h | 1
>> arch/powerpc/kernel/exceptions-64s.S | 42 +++++++++++++++++++++
>> arch/powerpc/kernel/mce.c | 16 +++++++-
>> arch/powerpc/mm/slb.c | 6 +++
>> arch/powerpc/platforms/pseries/pseries.h | 1
>> arch/powerpc/platforms/pseries/ras.c | 51
>> +++++++++++++++++++++++++
>> arch/powerpc/platforms/pseries/setup.c | 1
>> 8 files changed, 116 insertions(+), 3 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 ffe7c71e1132..fe447e0d4140 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);
>> + int (*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 f283958129f2..0038596b7906 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 +346,45 @@ 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 */
>> +
>> + /* Move original SRR0 and SRR1 into the respective regs */
>> + 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
>> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
>> index efdd16a79075..221271c96a57 100644
>> --- a/arch/powerpc/kernel/mce.c
>> +++ b/arch/powerpc/kernel/mce.c
>> @@ -488,9 +488,21 @@ 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)
>> + /*
>> + * See if platform is capable of handling machine check.
>> + * Otherwise fallthrough and allow CPU to handle this machine check.
>> + */
>> + if (ppc_md.machine_check_early)
>> + handled = ppc_md.machine_check_early(regs);
>> + else if (cur_cpu_spec && cur_cpu_spec->machine_check_early)
>> handled = cur_cpu_spec->machine_check_early(regs);
>> return handled;
>> }
>
> This looks fine to me after Michal's patch. Not sure if you want to
> fold them or add his immediately after this one in your series.
I am planning to fold Michal's patch into this patch itself.
>
>> diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
>> index 66577cc66dc9..5b1813b98358 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;
>> +}
>
>
> I think this should do something more like flush_and_reload_slb from
> powernv machine check code. We are real mode so should invalidate all
> SLBs.
Yes, and I think even powernv code should use this one instead. But that
can be a separate patch.
>
> It happens I also need very similar code (without the initial
> invalidate) for implementing idle wakeup code in C, so we should move
> that function and variants into mm/slb.c IMO.
So, you looking for only rebolt part ?
>
> Thanks,
> Nick
>
