Re: Design doc of adding ACPI support for arm64 on Xen - version 5

[Christoffer Dall <christoffer.dall@linaro.org>]

Hi Jan,

On Wed, Sep 02, 2015 at 02:41:36AM -0600, Jan Beulich wrote:
> >>> Shannon Zhao <zhaoshenglong@huawei.com> 09/02/15 8:03 AM >>>
> >There are some descriptions in Documentation/arm64/booting.txt of Linux:
> >
> >"The Image must be placed text_offset bytes from a 2MB aligned base
> >address near the start of usable system RAM and called there. Memory
> >below that base address is currently unusable by Linux, and therefore it
> >is strongly recommended that this location is the start of system RAM.
> >At least image_size bytes from the start of the image must be free for
> >use by the kernel."
> >
> >From this, it says "Memory below that base address is currently unusable
> >by Linux". So if we put these tables below Dom0 RAM address and even
> >describe these regions as RAM, the Linux could not use them.
> 
> May I remind you that a design should not take specific guest OS
> implementation details (which even for that one OS may change over time)
> as the basis for decisions?
> 
While I agree that the guest behavior should not dictate an unfortunate
design, surely factoring in the behavior of the expected guests in the
design is a reasonable thing to do?

Changing the boot requirements of Linux for an architecture is a really
invasive change, IMHO, and should be avoided if possible.

Are there other acceptable solutions for placing the EFI tables
somewhere else that would work?

Thanks,
-Christoffer