Re: [Xen-devel] loading custom ACPI tables?

[Eric Shelton <eshelton@xxxxxxxxx>]

Unfortunately, I managed to hit the few portions looked at by the
hypervisor, as I am modifying the IOAPIC information in MADT and IVRS
(as well as PCI slot interrupt info in DSDT, although that does not
appear to be looked at by the hypervisor).

A question on how Xen gathers platform info: Xen appears to use the MP
tables as a starting point for determining the number of IOAPICs.  Is
the hypervisor code capable of not using the MP tables, and solely
collecting this information from ACPI?  It would be nice not to

In terms of implementing passing in custom ACPI tables, I was
considering adding an additional "module" line in the grub
configuration (assuming a third one is permitted) to essentially a
copy of the in-memory structure, and looking for a magic number (which
will likely already be part of the ACPI tables).  I am aware of, but I
have not reviewed, the Linux initrd-based override code.  However, I'm
not sure whether the Xen development philosophy would prefer (1) code
reuse (if reasonably portable), even if it involves adding something
with the complexity of digging through an initrd; or (2) something
simpler with fewer LOC.  Other suggestions are welcome.

- Eric


On Mon, Apr 22, 2013 at 3:21 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 21.04.13 at 19:25, Eric Shelton <eshelton@xxxxxxxxx> wrote:
>> For some items I am working on, I need to modify a couple of the ACPI
>> tables.  Is there a preexisting way to provide replacement tables that
>> will be used by the hypervisor and dom0?
>
> For the hypervisor - no. But you'll not normally need to modify the
> (few) tables the hypervisor looks at.
>
> For the kernel, iirc support had been floating around for quite some
> time and got added relatively recently upstream (see
> CONFIG_ACPI_INITRD_TABLE_OVERRIDE). Plus there has been,
> for quite a bit longer a period already, a config option to add a DSDT
> replacement at build time (CONFIG_ACPI_CUSTOM_DSDT{,_FILE}).
>
> Jan
>

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