[Bug 211746] [Hyper-V] UEFI VM can't boot from the iso installation disk

bugzilla-noreply at freebsd.org bugzilla-noreply at freebsd.org
Mon Feb 13 17:27:30 UTC 2017


--- Comment #6 from Marcel Moolenaar <marcel at FreeBSD.org> ---
Check in the EFI memory map whether there's runtime-persistent memory at
0x200000 + 45MB (or abouts). Runtime persistent memory are memory allocations
of type runtime, firmware, (e.g. ACPI non-reclaimable), etc. I.e anything that
the kernel can't use during runtime. If the memory at 0x200000 isn't free
during runtime, then we have a real problem...

Some background: FreeBSD makes an invalid or at least a questionable assumption
that the memory map under EFI is compatible with the memory layout as seen
under the BIOS. As time goes by, this will probably be less and less valid. The
staging area is a side-effect of the kernel wanting to be loaded in a
contiguous memory region, starting at 0x200000. Something that is can't be done
under EFI without a staging area.

To wit: The old (and now removed) Itanium kernel used a virtual address space
for the kernel. The contiguous virtual kernel address mapped to underlying EFI
allocated pages that didn't have to be contiguous. On Itanium the physical
memory map could be without addressable memory in the first 4GB even, so no
amount of staging would be able to handle that.

Hopefully the problem is much more trivial than all of that...

You are receiving this mail because:
You are the assignee for the bug.

More information about the freebsd-virtualization mailing list