On Thu, Jan 19, 2017 at 02:09:37AM -0700, Jan Beulich wrote: > >>> On 18.01.17 at 20:51, <andrew.coop...@citrix.com> wrote: > > On 18/01/17 14:17, Doug Goldstein wrote: > >> +.Lefi_multiboot2_proto: > >> + /* Zero EFI SystemTable and EFI ImageHandle addresses. */ > >> + xor %esi,%esi > >> + xor %edi,%edi > >> + > >> + /* Skip Multiboot2 information fixed part. */ > >> + lea (MB2_fixed_sizeof+MULTIBOOT2_TAG_ALIGN-1)(%rbx),%ecx > >> + and $~(MULTIBOOT2_TAG_ALIGN-1),%ecx > > > > Are we strictly guaranteed to have the entire image, including multiboot > > tags, loaded below 4GB virtual even in the 64bit case? Even on non-EFI > > capable grub2's ? > > I can't speak for GrUB, but I've recently learned that EFI alone
GRUB is able to enforce 4 GiB restriction. At least right now. However, I am afraid that sooner or later machines will appear in the wild which do not have memory below 4 GiB (well, they must have some below 1 MiB but everything above is not a must as I know) or everything will be reserved/used by EFI boot/runtime services, etc. Then GRUB will also fail and we will be forced to extend multiboot2 proto further. However, it looks that current solution should not change much then. > doesn't appear to make such guarantees, and also doesn't look > to have ways to request such address restricted loading of an Why? Due to lack of memory below 4 GiB, it being reserved for something, EFI implementation bugs or anything else? Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel