linux-kernel - Re: [PATCH v2 2/2] x86/mce: Report only DRAM ECC as memory errors on AMD systems

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Date:   Sun, 10 Dec 2017 17:18:24 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Yazen Ghannam <Yazen.Ghannam@....com>
Cc:     linux-edac@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] x86/mce: Report only DRAM ECC as memory errors on
 AMD systems

On Thu, Dec 07, 2017 at 02:39:55PM -0600, Yazen Ghannam wrote:
> From: Yazen Ghannam <yazen.ghannam@....com>
> 
> The MCA_STATUS[ErrorCodeExt] field is very bank type specific. We currently
> check if the ErrorCodeExt value is 0x0 or 0x8 in mce_is_memory_error(), but
> we don't check the bank. This means that we could flag non-memory errors as
> memory errors.
> 
> We know that we want to flag DRAM ECC errors as memory errors, so let's do
> those cases first. We can add more cases later when needed.
> 
> Check that bank type is UMC and xec is 0 on SMCA systems.
> 
> Check that bank is 4 (Northbridge) and xec is 8 on legacy systems.
> 
> Define a wrapper function in mce_amd.c so we can use SMCA enums.
> 
> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> ---
> Link:
> https://lkml.kernel.org/r/20171201155034.39206-2-Yazen.Ghannam@amd.com
> 
> v1->v2:
> * No changes.
> 
>  arch/x86/include/asm/mce.h           |  2 ++
>  arch/x86/kernel/cpu/mcheck/mce.c     |  4 +---
>  arch/x86/kernel/cpu/mcheck/mce_amd.c | 11 +++++++++++
>  3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
> index b1e8d8db921f..96ea4b5ba658 100644
> --- a/arch/x86/include/asm/mce.h
> +++ b/arch/x86/include/asm/mce.h
> @@ -376,6 +376,7 @@ struct smca_bank {
>  extern struct smca_bank smca_banks[MAX_NR_BANKS];
>  
>  extern const char *smca_get_long_name(enum smca_bank_types t);
> +extern bool amd_mce_is_memory_error(struct mce *m);
>  
>  extern int mce_threshold_create_device(unsigned int cpu);
>  extern int mce_threshold_remove_device(unsigned int cpu);
> @@ -384,6 +385,7 @@ extern int mce_threshold_remove_device(unsigned int cpu);
>  
>  static inline int mce_threshold_create_device(unsigned int cpu) { return 0; };
>  static inline int mce_threshold_remove_device(unsigned int cpu) { return 0; };
> +static inline bool amd_mce_is_memory_error(struct mce *m) { return false; };
>  
>  #endif
>  
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index b1d616d08eee..321c7a80be66 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -503,10 +503,8 @@ static int mce_usable_address(struct mce *m)
>  bool mce_is_memory_error(struct mce *m)
>  {
>  	if (m->cpuvendor == X86_VENDOR_AMD) {
> -		/* ErrCodeExt[20:16] */
> -		u8 xec = (m->status >> 16) & 0x1f;
> +		return amd_mce_is_memory_error(m);
>  
> -		return (xec == 0x0 || xec == 0x8);
>  	} else if (m->cpuvendor == X86_VENDOR_INTEL) {
>  		/*
>  		 * Intel SDM Volume 3B - 15.9.2 Compound Error Codes
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index 219d5115f4d4..2b7f7ce4bedf 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -750,6 +750,17 @@ int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *sys_addr)
>  }
>  EXPORT_SYMBOL_GPL(umc_normaddr_to_sysaddr);
>  
> +bool amd_mce_is_memory_error(struct mce *m)
> +{
> +	/* ErrCodeExt[20:16] */
> +	u8 xec = (m->status >> 16) & 0x1f;
> +
> +	if (mce_flags.smca)
> +		return (smca_get_bank_type(m) == SMCA_UMC && xec == 0x0);
> +
> +	return (m->bank == 4 && xec == 0x8);

You don't need brackets around the return statements.

Anyway, applied, thx.


-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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