Re: fixed location of share info page in HVM guests

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Tue, Aug 28, 2012 at 02:35:19PM +0100, Keir Fraser wrote:
> On 28/08/2012 13:42, "Olaf Hering" <olaf@aepfle.de> wrote:
> 
> > On Tue, Aug 28, Keir Fraser wrote:
> > 
> >> Okay, that was a bit too clever, trying to hide between IOAPIC and LAPIC
> >> pages. How about a bit lower in memory -- FE700000-FE7FFFFF?
> >> 
> >> Everything in range FC000000-FFFFFFFF should already be marked
> >> E820_RESERVED. You can test that, and also see
> >> tools/firmware/hvmloader/e820.c:build_e820_table() (and note that
> >> RESERVED_MEMBASE == FC000000).
> > 
> > Yes, FC000000-FFFFFFFF has already an E820_RESERVED entry. Within that
> > range the kernel finds the IOAPIC, LAPIC and the HPET, perhaps because
> > they are listed in the ACPI table or because they are found by other
> > ways.
> 
> Yes they are all listed in various ACPI tables.
> 
> > To make the location of the of the shared pages configurable from the
> > tools, does tools/firmware/hvmloader/acpi/dsdt.asl have a way to
> > describe such special region? Maybe the kernel parses that table early

Isn't there also a magic string of said structure? If so we should also
check for the magic string to make sure we are mapping the proper
"thing." It can be done similary to how iBFT or EBDA is found.