linux-kernel - Re: [PATCH V2 1/9] acpi: apei: read ack upon ghes record consumption

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Date:	Wed, 6 Apr 2016 16:53:36 +0100
From:	Suzuki K Poulose <Suzuki.Poulose@....com>
To:	Tyler Baicar <tbaicar@...eaurora.org>, fu.wei@...aro.org,
	timur@...eaurora.org, harba@...eaurora.org,
	rruigrok@...eaurora.org, ahs3@...hat.com, catalin.marinas@....com,
	will.deacon@....com, rjw@...ysocki.net, lenb@...nel.org,
	matt@...eblueprint.co.uk, robert.moore@...el.com,
	lv.zheng@...el.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-efi@...r.kernel.org, devel@...ica.org
Cc:	"Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>,
	Naveen Kaje <nkaje@...eaurora.org>
Subject: Re: [PATCH V2 1/9] acpi: apei: read ack upon ghes record consumption

On 06/04/16 16:12, 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@...eaurora.org>
> Signed-off-by: Richard Ruigrok <rruigrok@...eaurora.org>
> Signed-off-by: Tyler Baicar <tbaicar@...eaurora.org>
> Signed-off-by: Naveen Kaje <nkaje@...eaurora.org>


>   		return ERR_PTR(-ENOMEM);
> +
> +	hest_hdr = (struct acpi_hest_header *)generic;
> +	if (hest_hdr->type == ACPI_HEST_TYPE_GENERIC_ERROR_V2) {
> +		ghes->generic_v2 = (struct acpi_hest_generic_v2 *)generic;
> +		rc = apei_map_generic_address(
> +			&ghes->generic_v2->read_ack_register);
> +		if (rc)
> +			goto err_unmap;
> +	} else
> +		ghes->generic_v2 = NULL;

...

>   err_unmap:
>   	apei_unmap_generic_address(&generic->error_status_address);
> +	if (ghes->generic_v2)
> +		apei_unmap_generic_address(
> +			&ghes->generic_v2->read_ack_register);
>   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 (ghes->generic_v2)
> +		apei_unmap_generic_address(
> +			&ghes->generic_v2->error_status_address);

I am not familiar with the APEI code, but is this error_status_address or
read_ack_register ? We don't seem to be mapping error_status_address in generic_v2 header
which is introduced in this patch ? Am I missing something ?

Suzuki