On 07/19, Dan Williams wrote:
> On Mon, Jul 18, 2016 at 5:45 PM, Vishal Verma <vishal.l.verma@xxxxxxxxx> wrote:
> > When a latent (unknown to 'badblocks') error is encountered, it will
> > trigger a machine check exception. On a system with machine check
> > recovery, this will only SIGBUS the process(es) which had the bad page
> > mapped (as opposed to a kernel panic on platforms without machine
> > check recovery features). In the former case, we want to trigger a full
> > rescan of that nvdimm bus. This will allow any additional, new errors
> > to be captured in the block devices' badblocks lists, and offending
> > operations on them can be trapped early, avoiding machine checks.
> >
> > This is done by registering a callback function with the
> > x86_mce_decoder_chain and calling the new ars_rescan functionality with
> > the address in the mce notificatiion.
> >
> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Cc: Tony Luck <tony.luck@xxxxxxxxx>
> > Cc: <linux-acpi@xxxxxxxxxxxxxxx>
> > Cc: <linux-nvdimm@xxxxxxxxxxxx>
> > Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> > ---
> > drivers/acpi/nfit.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > drivers/acpi/nfit.h | 1 +
> > 2 files changed, 103 insertions(+)
> >
> > diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
> > index def9505..0d2d7a3 100644
> > --- a/drivers/acpi/nfit.c
> > +++ b/drivers/acpi/nfit.c
> > @@ -12,6 +12,7 @@
> > */
> > #include <linux/list_sort.h>
> > #include <linux/libnvdimm.h>
> > +#include <linux/notifier.h>
> > #include <linux/module.h>
> > #include <linux/mutex.h>
> > #include <linux/ndctl.h>
> > @@ -23,6 +24,7 @@
> > #include <linux/io.h>
> > #include <linux/nd.h>
> > #include <asm/cacheflush.h>
> > +#include <asm/mce.h>
> > #include "nfit.h"
> >
> > /*
> > @@ -50,6 +52,9 @@ module_param(disable_vendor_specific, bool, S_IRUGO);
> > MODULE_PARM_DESC(disable_vendor_specific,
> > "Limit commands to the publicly specified set\n");
> >
> > +static LIST_HEAD(acpi_descs);
> > +static DEFINE_MUTEX(acpi_desc_lock);
> > +
> > static struct workqueue_struct *nfit_wq;
> >
> > struct nfit_table_prev {
> > @@ -2382,6 +2387,7 @@ static int acpi_nfit_check_deletions(struct acpi_nfit_desc *acpi_desc,
> >
> > int acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, acpi_size sz)
> > {
> > + struct acpi_nfit_desc *acpi_desc_entry;
> > struct device *dev = acpi_desc->dev;
> > struct nfit_table_prev prev;
> > const void *end;
> > @@ -2439,6 +2445,25 @@ int acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, acpi_size sz)
> >
> > rc = acpi_nfit_register_regions(acpi_desc);
> >
> > + /*
> > + * We may get here due to an update of the nfit via _FIT.
> > + * Check if the acpi_desc we're (re)initializing is already
> > + * present in the list, and if so, don't re-add it
> > + */
> > + mutex_lock(&acpi_desc_lock);
> > + if (list_empty(&acpi_descs))
> > + list_add_tail(&acpi_desc->list, &acpi_descs);
>
> No need to special case list_empty(), it's covered below and this
> isn't a fast path.
>
> > + else {
> > + int found = 0;
> > +
> > + list_for_each_entry(acpi_desc_entry, &acpi_descs, list)
> > + if (acpi_desc_entry == acpi_desc)
> > + found = 1;
> > + if (found == 0)
> > + list_add_tail(&acpi_desc->list, &acpi_descs);
> > + }
> > + mutex_unlock(&acpi_desc_lock);
> > +
> > out_unlock:
> > mutex_unlock(&acpi_desc->init_mutex);
> > return rc;
> > @@ -2522,6 +2547,69 @@ static int acpi_nfit_ars_rescan(struct nvdimm_bus_descriptor *nd_desc)
> > return 0;
> > }
> >
> > +static int nfit_handle_mce(struct notifier_block *nb, unsigned long val,
> > + void *data)
> > +{
> > + struct mce *mce = (struct mce *)data;
> > + struct acpi_nfit_desc *acpi_desc;
> > + struct nfit_spa *nfit_spa;
> > +
> > + /* We only care about memory errors */
> > + if (!(mce->status & MCACOD))
> > + return NOTIFY_DONE;
> > +
> > + /*
> > + * mce->addr contains the physical addr accessed that caused the
> > + * machine check. We need to walk through the list of NFITs, and see
> > + * if any of them matches that address, and only then start a scrub.
> > + */
> > + mutex_lock(&acpi_desc_lock);
> > + if (list_empty(&acpi_descs))
> > + goto out;
>
> Again, no need to check for empty, list_for_each_entry() already does that...
>
> > +
> > + list_for_each_entry(acpi_desc, &acpi_descs, list) {
> > + struct device *dev = acpi_desc->dev;
> > + int found_match = 0;
> > +
> > + list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
> > + struct acpi_nfit_system_address *spa = nfit_spa->spa;
> > +
> > + if (nfit_spa_type(spa) != NFIT_SPA_PM)
> > + continue;
> > + /* find the spa that covers the mce addr */
> > + if (spa->address > mce->addr)
> > + continue;
> > + if ((spa->address + spa->length - 1) < mce->addr)
> > + continue;
> > + found_match = 1;
> > + dev_dbg(dev, "%s: addr in SPA %d (0x%llx, 0x%llx)\n",
> > + __func__, spa->range_index, spa->address,
> > + spa->length);
> > + /*
> > + * We can break at the first match because we're going
> > + * to rescan all the SPA ranges. There shouldn't be any
> > + * aliasing anyway.
> > + */
> > + break;
> > + }
> > +
> > + /*
> > + * We can ignore an -EBUSY here because if an ARS is already
> > + * in progress, just let that be the last authoritative one
> > + */
> > + if (found_match)
> > + acpi_nfit_ars_rescan(&acpi_desc->nd_desc);
> > + }
> > +
> > + out:
> > + mutex_unlock(&acpi_desc_lock);
> > + return NOTIFY_DONE;
> > +}
> > +
> > +static struct notifier_block nfit_mce_dec = {
> > + .notifier_call = nfit_handle_mce,
> > +};
> > +
> > void acpi_nfit_desc_init(struct acpi_nfit_desc *acpi_desc, struct device *dev)
> > {
> > struct nvdimm_bus_descriptor *nd_desc;
> > @@ -2616,6 +2704,9 @@ static int acpi_nfit_remove(struct acpi_device *adev)
> > acpi_desc->cancel = 1;
> > flush_workqueue(nfit_wq);
> > nvdimm_bus_unregister(acpi_desc->nvdimm_bus);
> > + mutex_lock(&acpi_desc_lock);
> > + list_del(&acpi_desc->list);
> > + mutex_unlock(&acpi_desc_lock);
> > return 0;
> > }
> >
> > @@ -2725,13 +2816,24 @@ static __init int nfit_init(void)
> > if (!nfit_wq)
> > return -ENOMEM;
> >
> > + INIT_LIST_HEAD(&acpi_descs);
> > + mce_register_decode_chain(&nfit_mce_dec);
> > +
> > return acpi_bus_register_driver(&acpi_nfit_driver);
> > }
> >
> > static __exit void nfit_exit(void)
> > {
> > + struct acpi_nfit_desc *acpi_desc, *next;
> > +
> > + mce_unregister_decode_chain(&nfit_mce_dec);
> > acpi_bus_unregister_driver(&acpi_nfit_driver);
> > destroy_workqueue(nfit_wq);
> > + mutex_lock(&acpi_desc_lock);
> > + if (list_empty(&acpi_descs))
> > + list_for_each_entry_safe(acpi_desc, next, &acpi_descs, list)
> > + list_del(&acpi_desc->list);
>
> We should WARN here, since there should be no way, outside of a bug,
> that 'acpi_descs' is still populated after
> acpi_bus_unregister_driver().
Agreed, also just spotted another bug - it should've been
if (!list_empty()) ...
>
> > + mutex_unlock(&acpi_desc_lock);
> > }
> >
> > module_init(nfit_init);
> > diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
> > index db95c5d..cf4d42d 100644
> > --- a/drivers/acpi/nfit.h
> > +++ b/drivers/acpi/nfit.h
> > @@ -147,6 +147,7 @@ struct acpi_nfit_desc {
> > struct nd_cmd_ars_status *ars_status;
> > size_t ars_status_size;
> > struct work_struct work;
> > + struct list_head list;
> > unsigned int cancel:1;
> > unsigned long dimm_cmd_force_en;
> > unsigned long bus_cmd_force_en;
>
> Outside of the minor comments above, this looks good to me.
Ok, I'll fix these up and resend. Thanks!
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