Messages in this thread | | | Date | Sun, 22 Feb 2015 21:18:01 +0800 | From | Baoquan He <> | Subject | Re: [PATCH] x86, boot: Allow 64bit EFI kernel to be loaded above 4G |
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On 02/21/15 at 10:49am, Baoquan He wrote: > On 02/20/15 at 03:53pm, Yinghai Lu wrote: > > Then you are not setting the ident mapping correctly. > > > > you should make sure add extra ident mapping for the new [output, > > output+output_len - 1]. > > bootloader only cover old [output, output+output_len - 1] > > > > and you should check if the mapping is present before add new one, > > otherwise will overrite > > the one from 64bit bootloader like kexec-tools or grub2-x86_64 etc. > > > > You could use kernel_ident_mapping_init() from arch/x86/mm/init_64.c > > --- may need to cut and paste or split and include to > > arch/x86/boot/compressed/misc.c > > also you need to find some pages for alloc_pgt_page. > > At the beginning I did it just as you said, add IDT table and $PF > handler. Get page fault address and built ident mapping around it when > reload kernel above 4G. In this case 3 more pages are enough if kernel ~~ typo, it should be 4
> is put to another 512G and cross the boundary of 512G. > kernel_ident_mapping_init code can be borrowed and need be adjusted a > little bit. This works as expected, but a GPF reported and reboot to > BIOS. That's why I made a simple debug patch as I pasted before to > filter unnecessary interference. > > Since in arch/x86/boot/compressed/head_64.S 6 pages are used, 1 for pgd, > 1 for pud, 4 for pmd, all of them cover 0~4G ident mapping. So I added 4 > more pages as pmd, then 0~8G are covered. Now I hardcoded the output of > randomization of physical address as 5G, means kernel will be reloaded > there and decompressed. With these ident mapping for this hard coded > address should be correctly setted, still that GPF will happen. I > borrowed a printf.c from arch/x86/boot and made it work for > boot/compressed, can see in this case it will decompress successfully > and jump into arch/x86/kernel/head_64.S, then it reboot there during a > jump. > > > > > Thanks > > > > Yinghai
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