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* [PATCH v2] nfit, mce: only handle uncorrectable machine checks
@ 2018-10-25 18:06 Vishal Verma
  2018-10-25 18:54 ` Elliott, Robert (Persistent Memory)
  0 siblings, 1 reply; 2+ messages in thread
From: Vishal Verma @ 2018-10-25 18:06 UTC (permalink / raw)
  To: linux-nvdimm; +Cc: Tony Luck, stable, Borislav Petkov, linux-edac

The mce handler for 'nfit' devices is called for memory errors on a
Non-Volatile DIMM, and adds the error location to a 'badblocks' list.
This list is used by the various NVDIMM drivers to avoid consuming known
poison locations during IO.

The mce handler gets called for both corrected and uncorrectable errors.
Until now, both kinds of errors have been added to the badblocks list.
However, corrected memory errors indicate that the problem has already
been fixed by hardware, and the resulting interrupt is merely a
notification to Linux. As far as future accesses to that location are
concerned, it is perfectly fine to use, and thus doesn't need to be
included in the above badblocks list.

Add a check in the nfit mce handler to filter out corrected mce events,
and only process uncorrectable errors.

Reported-by: Omar Avelar <omar.avelar@intel.com>
Fixes: 6839a6d96f4e ("nfit: do an ARS scrub on hitting a latent media error")
Cc: stable@vger.kernel.org
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 arch/x86/include/asm/mce.h       | 1 +
 arch/x86/kernel/cpu/mcheck/mce.c | 3 ++-
 drivers/acpi/nfit/mce.c          | 4 ++--
 3 files changed, 5 insertions(+), 3 deletions(-)

v2: Reword the changelog to explain the motivation for this patch better
(Borisalv)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 3a17107594c8..3111b3cee2ee 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -216,6 +216,7 @@ static inline int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *s
 
 int mce_available(struct cpuinfo_x86 *c);
 bool mce_is_memory_error(struct mce *m);
+bool mce_is_correctable(struct mce *m);
 
 DECLARE_PER_CPU(unsigned, mce_exception_count);
 DECLARE_PER_CPU(unsigned, mce_poll_count);
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 953b3ce92dcc..27015948bc41 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -534,7 +534,7 @@ bool mce_is_memory_error(struct mce *m)
 }
 EXPORT_SYMBOL_GPL(mce_is_memory_error);
 
-static bool mce_is_correctable(struct mce *m)
+bool mce_is_correctable(struct mce *m)
 {
 	if (m->cpuvendor == X86_VENDOR_AMD && m->status & MCI_STATUS_DEFERRED)
 		return false;
@@ -544,6 +544,7 @@ static bool mce_is_correctable(struct mce *m)
 
 	return true;
 }
+EXPORT_SYMBOL_GPL(mce_is_correctable);
 
 static bool cec_add_mce(struct mce *m)
 {
diff --git a/drivers/acpi/nfit/mce.c b/drivers/acpi/nfit/mce.c
index e9626bf6ca29..7a51707f87e9 100644
--- a/drivers/acpi/nfit/mce.c
+++ b/drivers/acpi/nfit/mce.c
@@ -25,8 +25,8 @@ static int nfit_handle_mce(struct notifier_block *nb, unsigned long val,
 	struct acpi_nfit_desc *acpi_desc;
 	struct nfit_spa *nfit_spa;
 
-	/* We only care about memory errors */
-	if (!mce_is_memory_error(mce))
+	/* We only care about uncorrectable memory errors */
+	if (!mce_is_memory_error(mce) || mce_is_correctable(mce))
 		return NOTIFY_DONE;
 
 	/*
-- 
2.17.1

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^ permalink raw reply	[flat|nested] 2+ messages in thread

* RE: [PATCH v2] nfit, mce: only handle uncorrectable machine checks
  2018-10-25 18:06 [PATCH v2] nfit, mce: only handle uncorrectable machine checks Vishal Verma
@ 2018-10-25 18:54 ` Elliott, Robert (Persistent Memory)
  0 siblings, 0 replies; 2+ messages in thread
From: Elliott, Robert (Persistent Memory) @ 2018-10-25 18:54 UTC (permalink / raw)
  To: 'Vishal Verma', linux-nvdimm
  Cc: Tony Luck, Borislav Petkov, stable, linux-edac



> -----Original Message-----
> From: Linux-nvdimm [mailto:linux-nvdimm-bounces@lists.01.org] On Behalf Of Vishal Verma
> Sent: Thursday, October 25, 2018 1:06 PM
...
> +++ b/drivers/acpi/nfit/mce.c
> @@ -25,8 +25,8 @@ static int nfit_handle_mce(struct notifier_block *nb, unsigned long val,
>  	struct acpi_nfit_desc *acpi_desc;
>  	struct nfit_spa *nfit_spa;
> 
> -	/* We only care about memory errors */
> -	if (!mce_is_memory_error(mce))
> +	/* We only care about uncorrectable memory errors */
> +	if (!mce_is_memory_error(mce) || mce_is_correctable(mce))
>  		return NOTIFY_DONE;

Another function that calls those functions, cec_add_mce(), also calls 
mce_usable_address() to ensure the address valid bit is set.  It doesn't
look like nfit_handle_mce() ever confirms that before proceeding to
use mce->addr (if it gets through that if statement).

---
Robert Elliott, HPE Persistent Memory


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^ permalink raw reply	[flat|nested] 2+ messages in thread

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