[PATCH] papr/scm: Add bad memory ranges to nvdimm bad ranges

[Vaibhav Jain]

Hi Santosh,

Some review comments below.

Santosh Sivaraj <santosh at fossix.org> writes:

> Subscribe to the MCE notification and add the physical address which
> generated a memory error to nvdimm bad range.
>
> Signed-off-by: Santosh Sivaraj <santosh at fossix.org>
> ---
>
> This patch depends on "powerpc/mce: Add MCE notification chain" [1].
>
> Unlike the previous series[2], the patch adds badblock registration only for
> pseries scm driver. Handling badblocks for baremetal (powernv) PMEM will be done
> later and if possible get the badblock handling as a common code.
>
> [1] https://lore.kernel.org/linuxppc-dev/20200330071219.12284-1-ganeshgr@linux.ibm.com/
> [2] https://lore.kernel.org/linuxppc-dev/20190820023030.18232-1-santosh@fossix.org/
>
> arch/powerpc/platforms/pseries/papr_scm.c | 96 ++++++++++++++++++++++-
>  1 file changed, 95 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index 0b4467e378e5..5012cbf4606e 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -12,6 +12,8 @@
>  #include <linux/libnvdimm.h>
>  #include <linux/platform_device.h>
>  #include <linux/delay.h>
> +#include <linux/nd.h>
> +#include <asm/mce.h>
>  
>  #include <asm/plpar_wrappers.h>
>  
> @@ -39,8 +41,12 @@ struct papr_scm_priv {
>  	struct resource res;
>  	struct nd_region *region;
>  	struct nd_interleave_set nd_set;
> +	struct list_head region_list;
>  };
>  
> +LIST_HEAD(papr_nd_regions);
> +DEFINE_MUTEX(papr_ndr_lock);
> +
>  static int drc_pmem_bind(struct papr_scm_priv *p)
>  {
>  	unsigned long ret[PLPAR_HCALL_BUFSIZE];
> @@ -372,6 +378,10 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
>  		dev_info(dev, "Region registered with target node %d and online node %d",
>  			 target_nid, online_nid);
>  
> +	mutex_lock(&papr_ndr_lock);
> +	list_add_tail(&p->region_list, &papr_nd_regions);
> +	mutex_unlock(&papr_ndr_lock);
> +
>  	return 0;
>  
>  err:	nvdimm_bus_unregister(p->bus);
> @@ -379,6 +389,68 @@ err:	nvdimm_bus_unregister(p->bus);
>  	return -ENXIO;
>  }
>  
> +void papr_scm_add_badblock(struct nd_region *region, struct nvdimm_bus *bus,
> +			   u64 phys_addr)
> +{
> +	u64 aligned_addr = ALIGN_DOWN(phys_addr, L1_CACHE_BYTES);
> +
> +	if (nvdimm_bus_add_badrange(bus, aligned_addr, L1_CACHE_BYTES)) {
> +		pr_err("Bad block registration for 0x%llx failed\n", phys_addr);
> +		return;
> +	}
> +
> +	pr_debug("Add memory range (0x%llx - 0x%llx) as bad range\n",
> +		 aligned_addr, aligned_addr + L1_CACHE_BYTES);
> +
> +	nvdimm_region_notify(region, NVDIMM_REVALIDATE_POISON);
> +}
> +
> +static int handle_mce_ue(struct notifier_block *nb, unsigned long val,
> +			 void *data)
> +{
> +	struct machine_check_event *evt = data;
> +	struct papr_scm_priv *p;
> +	u64 phys_addr;
> +	bool found = false;
> +
> +	if (evt->error_type != MCE_ERROR_TYPE_UE)
> +		return NOTIFY_DONE;
> +
> +	if (list_empty(&papr_nd_regions))
> +		return NOTIFY_DONE;
> +
> +	phys_addr = evt->u.ue_error.physical_address +
> +		(evt->u.ue_error.effective_address & ~PAGE_MASK);
Though it seems that you are trying to get the actual physical address
from the page aligned evt->u.ue_error.physical_address, it would be nice
if you could put a comment as to why you are doing this seemingly wierd
math with real and effective addresses here.
> +
> +	if (!evt->u.ue_error.physical_address_provided ||
> +	    !is_zone_device_page(pfn_to_page(phys_addr >> PAGE_SHIFT)))
> +		return NOTIFY_DONE;
> +
> +	/* mce notifier is called from a process context, so mutex is safe */
> +	mutex_lock(&papr_ndr_lock);
> +	list_for_each_entry(p, &papr_nd_regions, region_list) {
> +		struct resource res = p->res;
> +
> +		if (phys_addr >= res.start && phys_addr <= res.end) {
> +			found = true;
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&papr_ndr_lock);
> +
> +	if (!found)
> +		return NOTIFY_DONE;
> +
> +	papr_scm_add_badblock(p->region, p->bus, phys_addr);
I see a possible race between papr_scm_add_badblock() and
papr_scm_remove() as a bad block may be reported just remove a region is
disabled. Would recomment calling papr_scm_bad_block() in context of
papr_ndr_lock.

> +
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block mce_ue_nb = {
> +	.notifier_call = handle_mce_ue
> +};
> +
>  static int papr_scm_probe(struct platform_device *pdev)
>  {
>  	struct device_node *dn = pdev->dev.of_node;
> @@ -476,6 +548,10 @@ static int papr_scm_remove(struct platform_device *pdev)
>  {
>  	struct papr_scm_priv *p = platform_get_drvdata(pdev);
>  
> +	mutex_lock(&papr_ndr_lock);
> +	list_del(&(p->region_list));
> +	mutex_unlock(&papr_ndr_lock);
> +
>  	nvdimm_bus_unregister(p->bus);
>  	drc_pmem_unbind(p);
>  	kfree(p->bus_desc.provider_name);
> @@ -498,7 +574,25 @@ static struct platform_driver papr_scm_driver = {
>  	},
>  };
>  
> -module_platform_driver(papr_scm_driver);
> +static int __init papr_scm_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_driver_register(&papr_scm_driver);
> +	if (!ret)
> +		mce_register_notifier(&mce_ue_nb);
> +
> +	return ret;
> +}
> +module_init(papr_scm_init);
> +
> +static void __exit papr_scm_exit(void)
> +{
> +	mce_unregister_notifier(&mce_ue_nb);
> +	platform_driver_unregister(&papr_scm_driver);
> +}
> +module_exit(papr_scm_exit);
> +
>  MODULE_DEVICE_TABLE(of, papr_scm_match);
>  MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("IBM Corporation");
> -- 
> 2.25.1
>

-- 
Vaibhav Jain <vaibhav at linux.ibm.com>
Linux Technology Center, IBM India Pvt. Ltd.