From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad@kernel.org>
Subject: Re: ask a question about ERST
Date: Thu, 18 Oct 2012 08:06:29 -0400
Message-ID: <20121018120627.GA13485@localhost.localdomain>
References: <507FBE7F.3010403@oracle.com>
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To: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Ethan Zhao <ethan.zhao@oracle.com>, Feng Jin <joe.jin@oracle.com>, xen-devel <xen-devel@lists.xen.org>
List-Id: xen-devel@lists.xenproject.org

On Thu, Oct 18, 2012 at 04:31:59PM +0800, Zhenzhong Duan wrote:
> Hi maintainer,
> I found below patch reverted part of erst header size check.
> This lead to mismatch with kernel upstream code and erst disabled on
> some machine like X4170 M3/X3-2.
> According to the ACPI spec 4.0 and 5.0, the Serialization Header Length
> should be the length of Serialization Header.
> After revert below patch, xen succeed with erst table init.
> So could this patch be reverted now to match acpi spec and kernel upstream?

There was a discussion about this on xen-devel. Search for Jan and ERST
and I believe the idea was that an AMD machine needs to be checked
to figure out what to do.

> 
> [root@zhenzhong2 xen-unstable.hg]# hg export 23760
> # HG changeset patch
> # User Keir Fraser <keir@xen.org>
> # Date 1312909603 -3600
> # Node ID ae10d7804168c185166277bcef3b18ffc9227b66
> # Parent aca07ff1f0a59cc7ebb5ef76875229b7e99ba3ff
> ACPI ERST: Revert change to erst_check_table() to be more permissive.
> 
> Permits tables that apparently Xen cannot handle (causes boot failure
> on many systems).
> 
> Signed-off-by: Keir Fraser <keir@xen.org>
> 
> diff -r aca07ff1f0a5 -r ae10d7804168 xen/drivers/acpi/apei/erst.c
> --- a/xen/drivers/acpi/apei/erst.c Tue Aug 09 17:48:16 2011 +0100
> +++ b/xen/drivers/acpi/apei/erst.c Tue Aug 09 18:06:43 2011 +0100
> @@ -715,13 +715,7 @@
> 
> static int __init erst_check_table(struct acpi_table_erst *erst_tab)
> {
> - /*
> - * Some old BIOSes include the ACPI standard header in the ERST header
> - * length; new BIOSes do not. Our check allows for both methods.
> - */
> - if ((erst_tab->header_length !=
> - (sizeof(struct acpi_table_erst) - sizeof(erst_tab->header)))
> - && (erst_tab->header_length != sizeof(struct acpi_table_erst)))
> + if (erst_tab->header_length != sizeof(struct acpi_table_erst))
> return -EINVAL;
> if (erst_tab->header.length < sizeof(struct acpi_table_erst))
> return -EINVAL;

Gosh, your mailer mangled that patch :-)