Re: [Xen-devel] ask a question about ERST

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-10-18 at 09:31 +0100, 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?

Did you ask yourself *why* this patch was reverted and investigate what
has changed in order to resolve that situation?

As it happens this patch has been discussed on xen-devel just this week,
please check the archives.

> 
> [root@zhenzhong2 xen-unstable.hg]# hg export 23760
> # HG changeset patch
> # User Keir Fraser <keir@xxxxxxx>
> # 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@xxxxxxx>
> 
> 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;
> 
> 
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> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel



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