Re: [PATCH -v2 0/4] EFI 1:1 mapping

H. Peter Anvin
2013-06-21T16:43:10Z

On 06/21/2013 07:21 AM, Borislav Petkov wrote:
> On Fri, Jun 21, 2013 at 03:05:30AM -0700, H. Peter Anvin wrote:
>> If you cap it you are basically imposing a constraint on the firmware
>> and may not run properly (or at least have to turn off EFI runtime
>> calls with all that implies.)
>
> I don't want to cap EFI just for the fun of it but rather set a limit
> so that the next one who wants a chunk of the virtual address space can
> have a reliable limit from where she/he can start. Otherwise we won't
> know where EFI reliably ends...
>

We don't... and I don't think there is anything we can do about it. If
some messed-up firmware wants to map a terabyte we either refuse and
don't allow EFI runtime calls on that machine or we accept it.

Fortunately the space is extremely large and with growing down from a
known address it is less likely that we'll conflict with something.

>> It might be good to have a sanity check but it needs to be pretty
>> generous.
>
> 64 Gb generous enough?

Let's start there and see if we run into something that gives us trouble.

-hpa