NACK: [Zesty] [PATCH] powerpc/powernv: Flush console before platform error reboot
Kleber Souza
kleber.souza at canonical.com
Tue Jan 23 16:16:56 UTC 2018
On 11/29/17 13:12, Breno Leitao wrote:
> From: Nicholas Piggin <npiggin at gmail.com>
>
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1735159
>
> 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 <npiggin at gmail.com>
> Reviewed-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> (backported from commit b746e3e01e70d23ef53dcde1203ab78a1b7ac514)
> Signed-off-by: Breno Leitao <leitao at debian.org>
> ---
> arch/powerpc/include/asm/opal.h | 2 +-
> arch/powerpc/platforms/powernv/opal-hmi.c | 22 ++------
> arch/powerpc/platforms/powernv/opal.c | 88 ++++++++++++++++++-------------
> arch/powerpc/platforms/powernv/powernv.h | 2 +
> 4 files changed, 56 insertions(+), 58 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index 588fb1c..182dab4 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 c0a8201..cc5b7db 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;
> @@ -266,8 +268,6 @@ 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;
> @@ -283,23 +283,7 @@ 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 26b290c..372aa19 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -25,6 +25,9 @@
> #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 <asm/machdep.h>
> #include <asm/opal.h>
> @@ -436,10 +439,55 @@ 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_nmi_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 +503,7 @@ 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 6dbc0a1..a159d48 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
>
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