[PATCH v8 5/5] powernv/pseries: consolidate code for mce early handling.
Nicholas Piggin
npiggin at gmail.com
Thu Aug 23 19:02:58 AEST 2018
On Thu, 23 Aug 2018 14:13:13 +0530
Mahesh Jagannath Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:
> On 08/20/2018 05:04 PM, Nicholas Piggin wrote:
> > On Sun, 19 Aug 2018 22:38:39 +0530
> > Mahesh J Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:
> >
> >> From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> >>
> >> Now that other platforms also implements real mode mce handler,
> >> lets consolidate the code by sharing existing powernv machine check
> >> early code. Rename machine_check_powernv_early to
> >> machine_check_common_early and reuse the code.
> >>
> >> Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> >> ---
> >> arch/powerpc/kernel/exceptions-64s.S | 155 ++++++----------------------------
> >> 1 file changed, 28 insertions(+), 127 deletions(-)
> >>
> >> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> >> index 12f056179112..2f85a7baf026 100644
> >> --- a/arch/powerpc/kernel/exceptions-64s.S
> >> +++ b/arch/powerpc/kernel/exceptions-64s.S
> >> @@ -243,14 +243,13 @@ EXC_REAL_BEGIN(machine_check, 0x200, 0x100)
> >> SET_SCRATCH0(r13) /* save r13 */
> >> EXCEPTION_PROLOG_0(PACA_EXMC)
> >> BEGIN_FTR_SECTION
> >> - b machine_check_powernv_early
> >> + b machine_check_common_early
> >> FTR_SECTION_ELSE
> >> b machine_check_pSeries_0
> >> ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE)
> >> EXC_REAL_END(machine_check, 0x200, 0x100)
> >> EXC_VIRT_NONE(0x4200, 0x100)
> >> -TRAMP_REAL_BEGIN(machine_check_powernv_early)
> >> -BEGIN_FTR_SECTION
> >> +TRAMP_REAL_BEGIN(machine_check_common_early)
> >> EXCEPTION_PROLOG_1(PACA_EXMC, NOTEST, 0x200)
> >> /*
> >> * Register contents:
> >> @@ -306,7 +305,9 @@ BEGIN_FTR_SECTION
> >> /* Save r9 through r13 from EXMC save area to stack frame. */
> >> EXCEPTION_PROLOG_COMMON_2(PACA_EXMC)
> >> mfmsr r11 /* get MSR value */
> >> +BEGIN_FTR_SECTION
> >> ori r11,r11,MSR_ME /* turn on ME bit */
> >> +END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
> >> ori r11,r11,MSR_RI /* turn on RI bit */
> >> LOAD_HANDLER(r12, machine_check_handle_early)
> >> 1: mtspr SPRN_SRR0,r12
> >> @@ -325,7 +326,6 @@ BEGIN_FTR_SECTION
> >> andc r11,r11,r10 /* Turn off MSR_ME */
> >> b 1b
> >> b . /* prevent speculative execution */
> >> -END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
> >>
> >> TRAMP_REAL_BEGIN(machine_check_pSeries)
> >> .globl machine_check_fwnmi
> >> @@ -333,7 +333,7 @@ machine_check_fwnmi:
> >> SET_SCRATCH0(r13) /* save r13 */
> >> EXCEPTION_PROLOG_0(PACA_EXMC)
> >> BEGIN_FTR_SECTION
> >> - b machine_check_pSeries_early
> >> + b machine_check_common_early
> >> END_FTR_SECTION_IFCLR(CPU_FTR_HVMODE)
> >> machine_check_pSeries_0:
> >> EXCEPTION_PROLOG_1(PACA_EXMC, KVMTEST_PR, 0x200)
> >> @@ -346,103 +346,6 @@ 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 */
> >> - lhz r11,PACA_IN_MCE(r13)
> >> - cmpwi r11,0 /* Are we in nested machine check */
> >> - bne 0f /* Yes, we are. */
> >> - /* First machine check entry */
> >> - ld r1,PACAMCEMERGSP(r13) /* Use MC emergency stack */
> >> -0: subi r1,r1,INT_FRAME_SIZE /* alloc stack frame */
> >> - addi r11,r11,1 /* increment paca->in_mce */
> >> - sth r11,PACA_IN_MCE(r13)
> >> - /* Limit nested MCE to level 4 to avoid stack overflow */
> >> - cmpwi r11,MAX_MCE_DEPTH
> >> - bgt 1f /* Check if we hit limit of 4 */
> >> - 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
> >> - beq 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 */
> >> - beq 1f /* if !handled then panic */
> >> -
> >> - /* Stay on emergency stack and return from interrupt. */
> >> - LOAD_HANDLER(r10,mce_return)
> >> - mtspr SPRN_SRR0,r10
> >> - ld r10,PACAKMSR(r13)
> >> - mtspr SPRN_SRR1,r10
> >> - RFI_TO_KERNEL
> >> - b .
> >> -
> >> -1: 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 .
> >> -
> >> - /* 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
> >> - /* Decrement paca->in_mce. */
> >> - lhz r12,PACA_IN_MCE(r13)
> >> - subi r12,r12,1
> >> - sth r12,PACA_IN_MCE(r13)
> >> - 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
> >> @@ -541,6 +444,9 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
> >> bl machine_check_early
> >> std r3,RESULT(r1) /* Save result */
> >> ld r12,_MSR(r1)
> >> +BEGIN_FTR_SECTION
> >> + b 4f
> >> +END_FTR_SECTION_IFCLR(CPU_FTR_HVMODE)
> >>
> >> #ifdef CONFIG_PPC_P7_NAP
> >> /*
> >> @@ -564,10 +470,11 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
> >> */
> >> rldicl. r11,r12,4,63 /* See if MC hit while in HV mode. */
> >> beq 5f
> >> - andi. r11,r12,MSR_PR /* See if coming from user. */
> >> +4: andi. r11,r12,MSR_PR /* See if coming from user. */
> >> bne 9f /* continue in V mode if we are. */
> >>
> >> 5:
> >> +BEGIN_FTR_SECTION
> >> #ifdef CONFIG_KVM_BOOK3S_64_HANDLER
> >> /*
> >> * We are coming from kernel context. Check if we are coming from
> >> @@ -578,6 +485,7 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
> >> cmpwi r11,0 /* Check if coming from guest */
> >> bne 9f /* continue if we are. */
> >> #endif
> >> +END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
> >
> > Put these inside the ifdef?
> >
> >
> >> /*
> >> * At this point we are not sure about what context we come from.
> >> * Queue up the MCE event and return from the interrupt.
> >> @@ -611,6 +519,7 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
> >> cmpdi r3,0 /* see if we handled MCE successfully */
> >>
> >> beq 1b /* if !handled then panic */
> >> +BEGIN_FTR_SECTION
> >> /*
> >> * Return from MC interrupt.
> >> * Queue up the MCE event so that we can log it later, while
> >> @@ -619,10 +528,24 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
> >> bl machine_check_queue_event
> >> MACHINE_CHECK_HANDLER_WINDUP
> >> RFI_TO_USER_OR_KERNEL
> >> +FTR_SECTION_ELSE
> >> + /*
> >> + * pSeries: Return from MC interrupt. Before that stay on emergency
> >> + * stack and call machine_check_exception to log the MCE event.
> >> + */
> >> + LOAD_HANDLER(r10,mce_return)
> >> + mtspr SPRN_SRR0,r10
> >> + ld r10,PACAKMSR(r13)
> >> + mtspr SPRN_SRR1,r10
> >> + RFI_TO_KERNEL
> >> + b .
> >> +ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE)
> >
> > Do you still need mce_return? Why can't you consolidate it as well? ...
> > Hmm, okay so now I look back at patch 2, I don't think you should call
> > machine_check_exception there. You're supposed to call
> > machine_check_queue_event here and it will be handled by irq work.
>
> machine_check_queue_event does not handle RTAS mce event.
Yes it would need a bit of work.
> Also, we need
> to call fwnmi_release_errinfo() as early as possible which is why I am
> calling machine_check_exception() in mce_return path for pSeries.
> Otherwise if we get another MCE before calling fwnmi_release_errinfo()
> then lpar will get rebooted without any logs getting printed.
I think you can call that in your early handler, but then defer
the printing to the irq work.
Although hmm, maybe that's less of a problem now we do nmi_enter
in machine check exception so I think printk will use an NMI safe
buffer.
We have to be careful actually of soft irq state if we take a
machine check in an un-reconciled state or in the middle of
the irq replay code I'm not actually sure we do the right thing,
but that would be a bug in existing code too. And we definitely
have MSR[RI] vs DAR/DSISR bugs in existing code, sigh.
I don't know... maybe just push what you have and we'll try to do
some more fixes and cleanups on top of that.
Thanks,
Nick
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