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. 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
