Re: [PATCH V4 01/10] acpi: apei: read ack upon ghes record consumption

[Suzuki K Poulose <Suzuki.Poulose@arm.com>]

On 21/10/16 18:30, Tyler Baicar wrote:
> A RAS (Reliability, Availability, Serviceability) controller
> may be a separate processor running in parallel with OS
> execution, and may generate error records for consumption by
> the OS. If the RAS controller produces multiple error records,
> then they may be overwritten before the OS has consumed them.
>
> The Generic Hardware Error Source (GHES) v2 structure
> introduces the capability for the OS to acknowledge the
> consumption of the error record generated by the RAS
> controller. A RAS controller supporting GHESv2 shall wait for
> the acknowledgment before writing a new error record, thus
> eliminating the race condition.
>
> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
> Signed-off-by: Richard Ruigrok <rruigrok@codeaurora.org>
> Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
> Signed-off-by: Naveen Kaje <nkaje@codeaurora.org>
> ---
>  drivers/acpi/apei/ghes.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/acpi/apei/hest.c |  7 +++++--
>  include/acpi/ghes.h      |  5 ++++-
>  3 files changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 60746ef..7d020b0 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -45,6 +45,7 @@
>  #include <linux/aer.h>
>  #include <linux/nmi.h>
>
> +#include <acpi/actbl1.h>
>  #include <acpi/ghes.h>
>  #include <acpi/apei.h>
>  #include <asm/tlbflush.h>
> @@ -79,6 +80,10 @@
>  	((struct acpi_hest_generic_status *)				\
>  	 ((struct ghes_estatus_node *)(estatus_node) + 1))
>
> +#define HEST_TYPE_GENERIC_V2(ghes)				\
> +	((struct acpi_hest_header *)ghes->generic)->type ==	\
> +	 ACPI_HEST_TYPE_GENERIC_ERROR_V2
> +
>  /*
>   * This driver isn't really modular, however for the time being,
>   * continuing to use module_param is the easiest way to remain
> @@ -248,7 +253,15 @@ static struct ghes *ghes_new(struct acpi_hest_generic *generic)
>  	ghes = kzalloc(sizeof(*ghes), GFP_KERNEL);
>  	if (!ghes)
>  		return ERR_PTR(-ENOMEM);
> +
>  	ghes->generic = generic;
> +	if (HEST_TYPE_GENERIC_V2(ghes)) {
> +		rc = apei_map_generic_address(
> +			&ghes->generic_v2->read_ack_register);
> +		if (rc)
> +			goto err_unmap;

I think should be goto err_free, see more below.

> +	}
> +
>  	rc = apei_map_generic_address(&generic->error_status_address);
>  	if (rc)
>  		goto err_free;
> @@ -270,6 +283,9 @@ static struct ghes *ghes_new(struct acpi_hest_generic *generic)
>
>  err_unmap:
>  	apei_unmap_generic_address(&generic->error_status_address);
> +	if (HEST_TYPE_GENERIC_V2(ghes))
> +		apei_unmap_generic_address(
> +			&ghes->generic_v2->read_ack_register);

We might end up trying to unmap (error_status_address) which is not mapped
if we hit the error in mapping read_ack_register. The read_ack_register unmap
hunk should be moved below to err_free.


>  err_free:
>  	kfree(ghes);
>  	return ERR_PTR(rc);
> @@ -279,6 +295,9 @@ static void ghes_fini(struct ghes *ghes)
>  {
>  	kfree(ghes->estatus);
>  	apei_unmap_generic_address(&ghes->generic->error_status_address);
> +	if (HEST_TYPE_GENERIC_V2(ghes))
> +		apei_unmap_generic_address(
> +			&ghes->generic_v2->read_ack_register);
>  }
>
>  static inline int ghes_severity(int severity)
> @@ -648,6 +667,23 @@ static void ghes_estatus_cache_add(
>  	rcu_read_unlock();
>  }
>

> +static int ghes_do_read_ack(struct acpi_hest_generic_v2 *generic_v2)

nit: We are actually writing something to the read_ack_register. The names
read_ack_register (which may be as per standard) and more importantly the
function name (ghes_do_read_ack) sounds a bit misleading.

Rest looks fine to me.

Suzuki