Re: [PATCH] acpi, nfit: skip ARS on machine-check-recovery capable platforms

[Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> writes:

> If the platform supports machine-check-recovery then there is little
> reason to kick off opportunistic scrubs to collect a media error list.
> That initial scrub is only useful when it might prevent a kernel panic
> from consuming poison (a media error from memory).

How expensive is the scrub?  Even on platforms that support recoverable
machine checks, it's possible that you get one that is not recoverable.
You haven't sold me on this change.  ;-)

Cheers,
Jeff


> Cc: Vishal Verma <vishal.l.verma-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> ---
>  drivers/acpi/nfit/core.c |    6 ++++--
>  drivers/acpi/nfit/mce.c  |    7 +++++++
>  drivers/acpi/nfit/nfit.h |    5 +++++
>  3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 7361d00818e2..bbefd9516939 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -2500,10 +2500,12 @@ static void acpi_nfit_scrub(struct work_struct *work)
>  	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
>  		/*
>  		 * Flag all the ranges that still need scrubbing, but
> -		 * register them now to make data available.
> +		 * register them now to make data available. If the
> +		 * platform supports machine-check recovery then we skip
> +		 * these opportunistic scans.
>  		 */
>  		if (!nfit_spa->nd_region) {
> -			nfit_spa->ars_required = 1;
> +			nfit_spa->ars_required = is_ars_required();
>  			acpi_nfit_register_region(acpi_desc, nfit_spa);
>  		}
>  	}
> diff --git a/drivers/acpi/nfit/mce.c b/drivers/acpi/nfit/mce.c
> index e5ce81c38eed..1e6f1e7100f9 100644
> --- a/drivers/acpi/nfit/mce.c
> +++ b/drivers/acpi/nfit/mce.c
> @@ -92,6 +92,13 @@ static struct notifier_block nfit_mce_dec = {
>  	.notifier_call	= nfit_handle_mce,
>  };
>  
> +bool is_ars_required(void)
> +{
> +        if (static_branch_unlikely(&mcsafe_key))
> +                return false;
> +	return true;
> +}
> +
>  void nfit_mce_register(void)
>  {
>  	mce_register_decode_chain(&nfit_mce_dec);
> diff --git a/drivers/acpi/nfit/nfit.h b/drivers/acpi/nfit/nfit.h
> index fc29c2e9832e..925f2a3d896e 100644
> --- a/drivers/acpi/nfit/nfit.h
> +++ b/drivers/acpi/nfit/nfit.h
> @@ -211,6 +211,7 @@ int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc);
>  #ifdef CONFIG_X86_MCE
>  void nfit_mce_register(void);
>  void nfit_mce_unregister(void);
> +bool is_ars_required(void);
>  #else
>  static inline void nfit_mce_register(void)
>  {
> @@ -218,6 +219,10 @@ static inline void nfit_mce_register(void)
>  static inline void nfit_mce_unregister(void)
>  {
>  }
> +static inline bool is_ars_required(void)
> +{
> +	return true;
> +}
>  #endif
>  
>  int nfit_spa_type(struct acpi_nfit_system_address *spa);
>
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