Re: [PATCH v3 2/2] efi: efi_mem_reserve(): don't reserve through memblock after mm_init()

[Matt Fleming]

On Fri, 06 Jan, at 07:28:40PM, Ard Biesheuvel wrote:
> 
> This is my point exactly. But it appears efi_free_boot_services()
> occurs much later than I thought, and so there is a sizabe time window
> where SLAB is up but reservations can still be made. But we don't
> check whether efi_free_boot_services() has been called.

True. This has only been correct thus far because all code has been
audited, but adding a check to catch future offenders is a good idea.

> Another problem is that we never check that the reservation is
> covered by a BootServicesData region, which are the only ones that
> are guaranteed to be retained up to this point.

The runtime regions are guaranteed to be retained too.

Again, this shouldn't actually be a problem today, but the potential
for breakage here warrants some kind of check and loud warning.