On Thu, Jun 27, 2013 at 2:32 AM, Matthew Garrett [off-list ref] wrote:

On Wed, Jun 26, 2013 at 07:38:19AM -0700, James Bottomley wrote:

quoted

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?

We can probably get away with that now, but it does risk us ending up
with some firmware that expects to run in physical mode (boards designed
for Linux) and some firmware that expects to run in virtual mode (boards
designed for Windows). The degree of lockdown in the Windows ecosystem
at present means it's not a real problem at the moment, but if that ever
changes we're going to risk incompatibility.

What is the problem trying to be avoided by not using the virtual map?
Is it passing the virtual mapping data from one kernel to the next
when kexecing? Or something else?

g.