On 06/26/2013 07:38 AM, James Bottomley wrote: > On Wed, 2013-06-26 at 14:59 +0100, Matt Fleming wrote: >> On Wed, 26 Jun, at 03:53:11PM, Leif Lindholm wrote: >>> It's completely feasible, but we'd need to use a different method to do >>> the boot services call with a 1:1 mapping (idmap support is not available >>> until much later in the boot process). >> >> At least if you no longer relied upon the idmap we could potentially >> have a single efi_enter_virtual_mode() call-site in init/main.c, which >> would be nice. > > The fixed virtual address scheme currently being looked at for x86_64 to > make SetVirtualAddressMap() kexec invariant doesn't work on 32 bit > because the address space isn't big enough. For ARM, given that we've > much more opportunity to work with the vendors, can we just avoid > transitioning to a virtual address map and always just install a > physical mapping before doing efi calls? > What we could do on x86-32 is to map from 0xc0000000 downwards. It wouldn't be invariant across kernel builds with different user/kernel split... but I'm not sure we can win that one. The other option is to say sod it and just use straight 1:1 mapping on 32 bits... -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
