Date:	Wed, 16 Dec 2015 11:29:30 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	fu.wei@...aro.org
Cc:	linaro-acpi@...ts.linaro.org, linux-kernel@...r.kernel.org,
	zjzhang@...eaurora.org, tony.luck@...el.com, gong.chen@...el.com,
	ying.huang@...el.com, tomasz.nowicki@...aro.org,
	tekkamanninja@...il.com, graeme.gregory@...aro.org,
	al.stone@...aro.org, hanjun.guo@...aro.org, jcm@...hat.com,
	mark.rutland@....com, catalin.marinas@....com, will.deacon@....com,
	rjw@...ysocki.net, matt.fleming@...el.com,
	"Chen, Gong" <gong.chen@...ux.intel.com>
Subject: Re: [PATCH v2 1/2] acpi, apei: add Boot Error Record Table (BERT)
 support

On Wed, Aug 19, 2015 at 12:44:16AM +0800, fu.wei@...aro.org wrote:
> From: Huang Ying <ying.huang@...el.com>
> 
> Under normal circumstances, when a hardware error occurs, kernel will
> be notified via NMI, MCE or some other method, then kernel will
> process the error condition, report it, and recover it if possible.
> But sometime, the situation is so bad, so that firmware may choose to
> reset directly without notifying Linux kernel.
> 
> Linux kernel can use the Boot Error Record Table (BERT) to get the
> un-notified hardware errors that occurred in a previous boot. In this
> patch, the error information is reported via printk.
> 
> For more information about BERT, please refer to ACPI Specification
> version 6.0, section 18.3.1:
>   http://www.uefi.org/sites/default/files/resources/ACPI_6.0.pdf
> 
> [Tony: Applied some cleanups suggested by Fu Wei]
> [Fu Wei: delete EXPORT_SYMBOL_GPL(bert_disable), and do some cleanups]
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@...aro.org>
> Signed-off-by: Chen, Gong <gong.chen@...ux.intel.com>
> Tested-by: Jonathan (Zhixiong) Zhang <zjzhang@...eaurora.org>
> Tested-by: Fu Wei <fu.wei@...aro.org>
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> Signed-off-by: Fu Wei <fu.wei@...aro.org>
> ---
>  Documentation/kernel-parameters.txt |   3 +
>  drivers/acpi/apei/Makefile          |   2 +-
>  drivers/acpi/apei/bert.c            | 162 ++++++++++++++++++++++++++++++++++++
>  include/acpi/apei.h                 |   1 +
>  4 files changed, 167 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 1d6f045..7c6402c 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -554,6 +554,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  
>  	bootmem_debug	[KNL] Enable bootmem allocator debug messages.
>  
> +	bert_disable	[ACPI]
> +			Disable Boot Error Record Table (BERT) support.

Please document what that new parameter is good for.

> +
>  	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
>  	bttv.radio=	Most important insmod options are available as
>  			kernel args too.
> diff --git a/drivers/acpi/apei/Makefile b/drivers/acpi/apei/Makefile
> index 5d575a9..e50573d 100644
> --- a/drivers/acpi/apei/Makefile
> +++ b/drivers/acpi/apei/Makefile
> @@ -3,4 +3,4 @@ obj-$(CONFIG_ACPI_APEI_GHES)	+= ghes.o
>  obj-$(CONFIG_ACPI_APEI_EINJ)	+= einj.o
>  obj-$(CONFIG_ACPI_APEI_ERST_DEBUG) += erst-dbg.o
>  
> -apei-y := apei-base.o hest.o erst.o
> +apei-y := apei-base.o hest.o erst.o bert.o
> diff --git a/drivers/acpi/apei/bert.c b/drivers/acpi/apei/bert.c
> new file mode 100644
> index 0000000..1426227
> --- /dev/null
> +++ b/drivers/acpi/apei/bert.c
> @@ -0,0 +1,162 @@
> +/*
> + * APEI Boot Error Record Table (BERT) support
> + *
> + * Copyright 2011 Intel Corp.
> + *   Author: Huang Ying <ying.huang@...el.com>
> + *
> + * Under normal circumstances, when a hardware error occurs, kernel
> + * will be notified via NMI, MCE or some other method, then kernel
> + * will process the error condition, report it, and recover it if
> + * possible. But sometime, the situation is so bad, so that firmware
> + * may choose to reset directly without notifying Linux kernel.
> + *
> + * Linux kernel can use the Boot Error Record Table (BERT) to get the
> + * un-notified hardware errors that occurred in a previous boot.
> + *
> + * For more information about BERT, please refer to ACPI Specification
> + * version 4.0, section 17.3.1
> + *
> + * This file is licensed under GPLv2.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/acpi.h>
> +#include <linux/io.h>
> +
> +#include "apei-internal.h"
> +
> +#define BERT_PFX "BERT: "

This is done with pr_fmt

> +static int bert_disable;
> +
> +static void __init bert_print_all(struct acpi_hest_generic_status *region,
> +				  unsigned int region_len)
> +{
> +	struct acpi_hest_generic_status *estatus = region;
> +	int remain = region_len;
> +	u32 estatus_len;
> +	int first = 1;

	if (!estatus->block_status)
		return;

> +	while (remain > sizeof(struct acpi_hest_generic_status)) {
> +		/* No more error record */

			     ... records */

> +		if (!estatus->block_status)
> +			break;

This test should happen when you enter the function (see above) and when
you assign to estatus, i.e. below, at the end of the while loop body:

		estatus = (void *)estatus + estatus_len;
		if (!estatus->block_status)
			break;

> +
> +		estatus_len = cper_estatus_len(estatus);
> +		if (estatus_len < sizeof(struct acpi_hest_generic_status) ||
> +		    remain < estatus_len) {
> +			pr_err(FW_BUG BERT_PFX
> +			       "Invalid error status block with length %u\n",

				"Invalid status block length (%u)"

> +			       estatus_len);
> +			return;
> +		}
> +
> +		if (cper_estatus_check(estatus)) {
> +			pr_err(FW_BUG BERT_PFX "Invalid error status block\n");

						"Invalid error record."
> +			goto next;
> +		}
> +
> +		if (first) {
> +			pr_info(HW_ERR "Error record from previous boot:\n");

					Error records<--- plural.

> +			first = 0;
> +		}

We have pr_info_once() for this.

> +
> +		cper_estatus_print(KERN_INFO HW_ERR, estatus);
> +next:
> +		estatus = (void *)estatus + estatus_len;
> +		remain -= estatus_len;
> +	}
> +}
> +
> +static int __init setup_bert_disable(char *str)
> +{
> +	bert_disable = 1;
> +
> +	return 0;
> +}
> +__setup("bert_disable", setup_bert_disable);
> +
> +static int __init bert_check_table(struct acpi_table_bert *bert_tab)
> +{
> +	if (bert_tab->header.length < sizeof(struct acpi_table_bert))
> +		return -EINVAL;

\n here

> +	if (bert_tab->region_length &&

This test looks redundant if you're going to compare it to the size of
the BERT region struct below.

> +	    bert_tab->region_length < sizeof(struct acpi_bert_region))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static int __init bert_init(void)
> +{
> +	struct acpi_hest_generic_status *bert_region;
> +	struct acpi_table_bert *bert_tab;
> +	unsigned int region_len;
> +	acpi_status status;
> +	struct resource *r;
> +	int rc = -EINVAL;
> +
> +	if (acpi_disabled)
> +		goto out;
> +
> +	if (bert_disable) {
> +		pr_info(BERT_PFX "Boot Error Record Table (BERT) support is disabled.\n");
> +		goto out;
> +	}
> +
> +	status = acpi_get_table(ACPI_SIG_BERT, 0,
> +				(struct acpi_table_header **)&bert_tab);

No need to break that line, just leave it stick out.

> +	if (status == AE_NOT_FOUND) {
> +		pr_err(BERT_PFX "Table is not found!\n");

This will get issued on *all* machines which don't have BERT - which
is the majority now, I'm afraid - and that information is useless to
people. It's not like they can do anything about it short of overriding
their own firmware.

So please remove that printk.

> +		goto out;
> +	} else if (ACPI_FAILURE(status)) {
> +		const char *msg = acpi_format_exception(status);
> +
> +		pr_err(BERT_PFX "Failed to get table, %s\n", msg);
> +		goto out;
> +	}
> +
> +	rc = bert_check_table(bert_tab);
> +	if (rc) {
> +		pr_err(FW_BUG BERT_PFX "BERT table is invalid\n");

Prefix already has "BERT". Either write it out:

	"BERT: Boot Error Record Table invalid"

or make it shorter:

	"BERT: table invalid."

> +		goto out;
> +	}
> +
> +	region_len = bert_tab->region_length;
> +	if (!region_len) {
> +		rc = 0;
> +		goto out;
> +	}

Huh, we just checked ->region_length in bert_check_table(). This test is
redundant.

> +
> +	r = request_mem_region(bert_tab->address, region_len, "APEI BERT");
> +	if (!r) {
> +		pr_err(BERT_PFX "Can't request iomem region <%016llx-%016llx>\n",
> +		       (unsigned long long)bert_tab->address,
> +		       (unsigned long long)bert_tab->address + region_len - 1);
> +		rc = -EIO;
> +		goto out;
> +	}
> +
> +	bert_region = ioremap_cache(bert_tab->address, region_len);
> +	if (!bert_region) {
> +		rc = -ENOMEM;
> +		goto out_release;
> +	}
> +
> +	bert_print_all(bert_region, region_len);
> +
> +	iounmap(bert_region);
> +
> +out_release:
> +	release_mem_region(bert_tab->address, region_len);
> +out:
> +	if (rc)
> +		bert_disable = 1;

This assignment is redundant. We're not testing it anywhere else after
bert_init() has run.

> +
> +	return rc;
> +}
> +
> +late_initcall(bert_init);
> diff --git a/include/acpi/apei.h b/include/acpi/apei.h
> index 76284bb..284801a 100644
> --- a/include/acpi/apei.h
> +++ b/include/acpi/apei.h
> @@ -23,6 +23,7 @@ extern bool ghes_disable;
>  #else
>  #define ghes_disable 1
>  #endif
> +extern int bert_disable;
>  
>  #ifdef CONFIG_ACPI_APEI
>  void __init acpi_hest_init(void);
> -- 
> 2.4.3
> 
> 

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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