On Fri, Aug 12, 2022 at 1:18 AM Daniel Kiper <dki...@net-space.pl> wrote: > > On Thu, Aug 04, 2022 at 11:07:30PM +0800, Wei Zhang wrote: > > 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 > > This is what I expected. I appreciate your work. Sadly this is not > a direction which we are heading. So, I have to NAK your patch.
That's OK. This is just a random thought I had when I was going through the kernel boot code, and I'm happy that you took a look. > However, > if you want to improve the EFI boot protocol in the GRUB please take > a look at [1] and my comments starting at [2]. I would really want to > see the patch set at [1] updated and at some point merged into the GRUB > upstream. I haven't looked into it, but I'll take it if it's not too far beyond my scope:) > > If you have any questions please drop us a line. > > Daniel > > [1] https://lists.gnu.org/archive/html/grub-devel/2021-10/msg00209.html > [2] https://lists.gnu.org/archive/html/grub-devel/2021-11/msg00084.html Wei Zhang _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel