On Fri, 13 Aug 2010 15:19:56 -0700, "Eric W. Biederman" wrote: >Takao Indoh <indou.takao at jp.fujitsu.com> writes: > >> Hi all, >> >> The attached patch enables EFI to run in physical mode. >> >> Basically EFI is in physical mode at first and it's switched to virtual >> mode after calling SetVirtualAddressMap. By applying this patch, you can >> run EFI always in physical mode. And you can also specify "virtefi" as >> kernel boot parameter to run EFI in virtual mode as before. Note that >> this patch supports only x86_64. >> >> This is needed to run kexec/kdump in EFI-booted system. The following is >> an original discussion. In this thread, I explained that kdump does not >> work because EFI system table is modified by SetVirtualAddressMap. And >> the idea to run EFI in physical mode was proposed. This patch implements >> it. >> >> http://marc.info/?l=linux-kernel&m=128018221820234&w=2 >>> When the 1st kernel boots, EFI system table(efi_system_table_t) is >>> modified by SetVirtualAddressMap, which is one of EFI runtime service. >>> This runtime changes physical address in EFI system table to virtual >>> address. >>> >>> When the 2nd kernel boots, it also receives the same EFI system table, >>> and the address included in it is already virtual address(1st kernel >>> rewrote it). But 2nd kernel does not know that, 2nd kernel thinks it is >>> a physical address. This causes problems. >> >> Basic idea of this patch is to create EFI own pagetable. This pagetable >> maps physical address of EFI runtime to the virtual address which is the >> same value so that we can call it directly. For example, physical >> address 0x800000 is mapped to virtual address 0x800000. Before calling >> EFI runtime, cr3 register is switched to this pagetable, and restored >> when we come back from EFI. >> >> Any comments would be appreciated. >> >> Signed-off-by: Takao Indoh <indou.takao at jp.fujitsu.com> > >Acked-by: "Eric W. Biederman" <ebiederm at xmission.com> > >There is what appears to be unneeded redundancy (we need two >implementations of physciall calls into efi?), but that is confined to >the weird efi state. > >It is a shame you haven't done the little bit extra to get >efi_pagetable_init working on x86_32. Unfortunately I don't have a machine to test. The machine I'm using does not support EFI on x86_32:-( I'd appreciate it if anyone try it... Thanks, Takao Indoh > >Overall this seems sane and confined to the x86 efi, and it looks >like further improvements could easily be layered on top of this one. > >Eric
