[Xen-devel] Re: [PATCH][VTD] check BIOS settings before enabling interrupt remapping or x2apic

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 29.03.11 at 19:58, "Kay, Allen M" <allen.m.kay@xxxxxxxxx> wrote:
> Check flags field in ACPI DMAR structure before enabling interrupt remapping 
> or x2apic.  This allows platform vendors to disable interrupt remapping or 
> x2apic features if on board BIOS does not support them.
> 
> Signed-off-by: Allen Kay <allen.m.kay@xxxxxxxxx>

Taking a second look (while trying to merge this into our SLE11
code base), I think this

>@@ -761,7 +762,11 @@ out:
> 
> int __init acpi_dmar_init(void)
> {
>+    struct acpi_table_dmar *dmar;
>+
>     acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_table);
>+    dmar = (struct acpi_table_dmar *) dmar_table;
>+    dmar_flags = dmar->flags;
> 
>     return parse_dmar_table(acpi_parse_dmar);
> }

is wrong from a TXT perspective - the table obtained here must
only be used for the signature zapping activity, nothing else. All
decisions must be based upon what gets passed to
acpi_parse_dmar(). (This would at once reduce the size of
the change, since a cast struct acpi_table_dmar * is already
available there.)

Jan


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