On Mon, 02 Jul 2018 11:17:06 +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/powernv/opal.c | 1
> arch/powerpc/platforms/pseries/pseries.h | 1
> arch/powerpc/platforms/pseries/ras.c | 51
> +++++++++++++++++++++++++
> arch/powerpc/platforms/pseries/setup.c | 1
> 9 files changed, 116 insertions(+), 4 deletions(-)
>
> +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 */
Is there any reason you can't use the existing
machine_check_powernv_early code to do all this?
> 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);
Would be good to add a powernv ppc_md handler which does the
cur_cpu_spec->machine_check_early() call now that other platforms are
calling this code. Because those aren't valid as a fallback call, but
specific to powernv.
> diff --git a/arch/powerpc/platforms/powernv/opal.c
> b/arch/powerpc/platforms/powernv/opal.c
> index 48fbb41af5d1..ed548d40a9e1 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -417,7 +417,6 @@ static int opal_recover_mce(struct pt_regs *regs,
>
> if (!(regs->msr & MSR_RI)) {
> /* If MSR_RI isn't set, we cannot recover */
> - pr_err("Machine check interrupt unrecoverable: MSR(RI=0)\n");
What's the reason for this change?
> recovered = 0;
> } else if (evt->disposition == MCE_DISPOSITION_RECOVERED) {
> /* Platform corrected itself */
> diff --git a/arch/powerpc/platforms/pseries/pseries.h
> b/arch/powerpc/platforms/pseries/pseries.h
> index 60db2ee511fb..3611db5dd583 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 int 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..9aa7885e0148 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();
Should the fwnmi_release_errinfo be done in the realmode path as well
now, or is there some reason to leave it here?
> + errp = fwnmi_get_errlog();
> if (errp && recover_mce(regs, errp))
> return 1;
> }
>
> return 0;
> }
> +
> +int 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 60a067a6e743..249b02bc5c41 100644
> --- a/arch/powerpc/platforms/pseries/setup.c
> +++ b/arch/powerpc/platforms/pseries/setup.c
> @@ -999,6 +999,7 @@ 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,
>
