On 07/19/2017 12:29 PM, Nicholas Piggin wrote: > Unrecovered MCE and HMI errors are sent through a special restart OPAL > call to log the platform error. The downside is that they don't go > through normal Linux crash paths, so they don't give much information > to the Linux console. > > Change this by providing a special crash function which does some of > the console flushing from the panic() path before calling firmware to > reboot. > > The downside of this is a little more code to execute before reaching > the firmware reboot. However in practice, it's critical to get the > Linux console messages output in order to debug a problem. So this is > a desirable tradeoff. > > Note on the implementation: It is difficult to plumb a custom reboot > handler into the panic path, because panic does a little bit too much > work. For example, it will try to delay with the timebase, but that > may be corrupted in some cases resulting in a hang without reaching > the platform reboot. Another problem is that panic can invoke the > crash dump code which is not what we want in the case of a hardware > platform error. Long-term the best solution will be to rework the > panic path so it can be suitable for this kind of panic, but for now > we just duplicate a bit of the code. > > Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Reviewed-by: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com> Thanks, -Mahesh. > --- > arch/powerpc/include/asm/opal.h | 2 +- > arch/powerpc/platforms/powernv/opal-hmi.c | 22 ++------ > arch/powerpc/platforms/powernv/opal.c | 89 > ++++++++++++++++++------------- > arch/powerpc/platforms/powernv/powernv.h | 2 + > 4 files changed, 57 insertions(+), 58 deletions(-) > > diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h > index 588fb1c23af9..182dab435aad 100644 > --- a/arch/powerpc/include/asm/opal.h > +++ b/arch/powerpc/include/asm/opal.h > @@ -50,7 +50,7 @@ int64_t opal_tpo_write(uint64_t token, uint32_t > year_mon_day, > uint32_t hour_min); > int64_t opal_cec_power_down(uint64_t request); > int64_t opal_cec_reboot(void); > -int64_t opal_cec_reboot2(uint32_t reboot_type, char *diag); > +int64_t opal_cec_reboot2(uint32_t reboot_type, const char *diag); > int64_t opal_read_nvram(uint64_t buffer, uint64_t size, uint64_t offset); > int64_t opal_write_nvram(uint64_t buffer, uint64_t size, uint64_t offset); > int64_t opal_handle_interrupt(uint64_t isn, __be64 *outstanding_event_mask); > diff --git a/arch/powerpc/platforms/powernv/opal-hmi.c > b/arch/powerpc/platforms/powernv/opal-hmi.c > index 88f3c61eec95..d78fed728cdf 100644 > --- a/arch/powerpc/platforms/powernv/opal-hmi.c > +++ b/arch/powerpc/platforms/powernv/opal-hmi.c > @@ -30,6 +30,8 @@ > #include <asm/cputable.h> > #include <asm/machdep.h> > > +#include "powernv.h" > + > static int opal_hmi_handler_nb_init; > struct OpalHmiEvtNode { > struct list_head list; > @@ -267,8 +269,6 @@ static void hmi_event_handler(struct work_struct *work) > spin_unlock_irqrestore(&opal_hmi_evt_lock, flags); > > if (unrecoverable) { > - int ret; > - > /* Pull all HMI events from OPAL before we panic. */ > while (opal_get_msg(__pa(&msg), sizeof(msg)) == OPAL_SUCCESS) { > u32 type; > @@ -284,23 +284,7 @@ static void hmi_event_handler(struct work_struct *work) > print_hmi_event_info(hmi_evt); > } > > - /* > - * Unrecoverable HMI exception. We need to inform BMC/OCC > - * about this error so that it can collect relevant data > - * for error analysis before rebooting. > - */ > - ret = opal_cec_reboot2(OPAL_REBOOT_PLATFORM_ERROR, > - "Unrecoverable HMI exception"); > - if (ret == OPAL_UNSUPPORTED) { > - pr_emerg("Reboot type %d not supported\n", > - OPAL_REBOOT_PLATFORM_ERROR); > - } > - > - /* > - * Fall through and panic if opal_cec_reboot2() returns > - * OPAL_UNSUPPORTED. > - */ > - panic("Unrecoverable HMI exception"); > + pnv_platform_error_reboot(NULL, "Unrecoverable HMI exception"); > } > } > > diff --git a/arch/powerpc/platforms/powernv/opal.c > b/arch/powerpc/platforms/powernv/opal.c > index 9b87abb178f0..96436d129684 100644 > --- a/arch/powerpc/platforms/powernv/opal.c > +++ b/arch/powerpc/platforms/powernv/opal.c > @@ -25,6 +25,10 @@ > #include <linux/memblock.h> > #include <linux/kthread.h> > #include <linux/freezer.h> > +#include <linux/printk.h> > +#include <linux/kmsg_dump.h> > +#include <linux/console.h> > +#include <linux/sched/debug.h> > > #include <asm/machdep.h> > #include <asm/opal.h> > @@ -436,10 +440,55 @@ static int opal_recover_mce(struct pt_regs *regs, > return recovered; > } > > +void pnv_platform_error_reboot(struct pt_regs *regs, const char *msg) > +{ > + /* > + * This is mostly taken from kernel/panic.c, but tries to do > + * relatively minimal work. Don't use delay functions (TB may > + * be broken), don't crash dump (need to set a firmware log), > + * don't run notifiers. We do want to get some information to > + * Linux console. > + */ > + console_verbose(); > + bust_spinlocks(1); > + pr_emerg("Hardware platform error: %s\n", msg); > + if (regs) > + show_regs(regs); > + smp_send_stop(); > + printk_safe_flush_on_panic(); > + kmsg_dump(KMSG_DUMP_PANIC); > + bust_spinlocks(0); > + debug_locks_off(); > + console_flush_on_panic(); > + > + /* > + * Don't bother to shut things down because this will > + * xstop the system. > + */ > + if (opal_cec_reboot2(OPAL_REBOOT_PLATFORM_ERROR, msg) > + == OPAL_UNSUPPORTED) { > + pr_emerg("Reboot type %d not supported for %s\n", > + OPAL_REBOOT_PLATFORM_ERROR, msg); > + } > + > + /* > + * We reached here. There can be three possibilities: > + * 1. We are running on a firmware level that do not support > + * opal_cec_reboot2() > + * 2. We are running on a firmware level that do not support > + * OPAL_REBOOT_PLATFORM_ERROR reboot type. > + * 3. We are running on FSP based system that does not need > + * opal to trigger checkstop explicitly for error analysis. > + * The FSP PRD component would have already got notified > + * about this error through other channels. > + */ > + > + ppc_md.restart(NULL); > +} > + > int opal_machine_check(struct pt_regs *regs) > { > struct machine_check_event evt; > - int ret; > > if (!get_mce_event(&evt, MCE_EVENT_RELEASE)) > return 0; > @@ -455,43 +504,7 @@ int opal_machine_check(struct pt_regs *regs) > if (opal_recover_mce(regs, &evt)) > return 1; > > - /* > - * Unrecovered machine check, we are heading to panic path. > - * > - * We may have hit this MCE in very early stage of kernel > - * initialization even before opal-prd has started running. If > - * this is the case then this MCE error may go un-noticed or > - * un-analyzed if we go down panic path. We need to inform > - * BMC/OCC about this error so that they can collect relevant > - * data for error analysis before rebooting. > - * Use opal_cec_reboot2(OPAL_REBOOT_PLATFORM_ERROR) to do so. > - * This function may not return on BMC based system. > - */ > - ret = opal_cec_reboot2(OPAL_REBOOT_PLATFORM_ERROR, > - "Unrecoverable Machine Check exception"); > - if (ret == OPAL_UNSUPPORTED) { > - pr_emerg("Reboot type %d not supported\n", > - OPAL_REBOOT_PLATFORM_ERROR); > - } > - > - /* > - * We reached here. There can be three possibilities: > - * 1. We are running on a firmware level that do not support > - * opal_cec_reboot2() > - * 2. We are running on a firmware level that do not support > - * OPAL_REBOOT_PLATFORM_ERROR reboot type. > - * 3. We are running on FSP based system that does not need opal > - * to trigger checkstop explicitly for error analysis. The FSP > - * PRD component would have already got notified about this > - * error through other channels. > - * > - * If hardware marked this as an unrecoverable MCE, we are > - * going to panic anyway. Even if it didn't, it's not safe to > - * continue at this point, so we should explicitly panic. > - */ > - > - panic("PowerNV Unrecovered Machine Check"); > - return 0; > + pnv_platform_error_reboot(regs, "Unrecoverable Machine Check > exception"); > } > > /* Early hmi handler called in real mode. */ > diff --git a/arch/powerpc/platforms/powernv/powernv.h > b/arch/powerpc/platforms/powernv/powernv.h > index 6dbc0a1da1f6..a159d48573d7 100644 > --- a/arch/powerpc/platforms/powernv/powernv.h > +++ b/arch/powerpc/platforms/powernv/powernv.h > @@ -7,6 +7,8 @@ extern void pnv_smp_init(void); > static inline void pnv_smp_init(void) { } > #endif > > +extern void pnv_platform_error_reboot(struct pt_regs *regs, const char *msg) > __noreturn; > + > struct pci_dev; > > #ifdef CONFIG_PCI >