On Wed, Aug 3, 2022 at 11:33 PM Daniel Kiper <dki...@net-space.pl> wrote: > > On Sat, Jul 23, 2022 at 07:20:43PM +0800, Wei Zhang wrote: > > From: Wei Zhang <zhangwei...@gmail.com> > > > > Currently GRUB boots linux with 32-bit protocol for 64 bit kernel. > > Thus if both GRUB and linux kernel are in 64-bit, we'll have to go > > through 64-bit grub -> 32-bit boot protocol -> 64-bit kernel > > transitions, and extra instructions have to be executed in the kernel. > > > > Since linux has long ago supported 64-bit boot protocol, we can take > > advantage of that to directly boot to 64-bit kernel. > > > > To do this, first we determine whether the kernel is 64-bit by > > xloadflags (since linux boot protocol 2.12), then we build the > > identity-mapped page table required by the 64-bit kernel, and that's > > it. The memory needed by the page table is allocated after the > > protected kernel image proper. > > > > So if we're in 32-bit GRUB to boot a 64-bit kernel, the transition > > will happen before handing over to the kernel, and if we're in 64-bit > > GRUB, we don't have to go down to 32-bit and back to 64-bit. The > > 32-bit kernel boot process will not be affected. > > > > Tested on my 64-bit machine and QEMU. > > Could you tell us what target and platform you configure for the GRUB? > Or send us full GRUB configure command you use?
Sure, I mainly focused on x86, and my configure command is: ./configure --target=x86_64 --with-platform=efi I didn't examine other targets, e.g. arm64 and sparc64 etc. But if there are similar issues on those targets too, I'll definitely like to work on those too:) Thanks for your reply. Wei Zhang _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
