Re: [PATCH] x86/EFI: additional checks in efi_bgrt_init()

[Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>]

On Tue, Nov 06, 2012 at 08:57:06AM +0000, Jan Beulich wrote:
> The question here is how to properly invalidate that data then:
> So far I was assuming that clearing the valid bit would be the way
> to go, as the specification says nothing on e.g. the image address
> being zero having any specific meaning. I need to do that in Xen,
> at least for the time being, as I'm not inclined to postpone
> indefinitely the use of boot services memory for normal memory
> allocations (which we would have to do if we wanted Dom0 to
> be able to access the image pointed to here).

This doesn't postpone the use of boot services memory indefinitely; the
BGRT driver copies the image out, and the kernel then frees boot
services memory.  That does introduce a delay in the use of boot
services memory, but not an indefinite one.

> I was quite bad a design decision to allow (and even suggest)
> the image to live in boot services memory - one can't generally
> expect the ACPI parser to become available in an OS before
> setting up memory allocation. To Linux this already has turned
> out to be a problem, on Xen dealing with this would turn out
> even more cumbersome.

What problems has this caused?

- Josh Triplett