Re: [PATCH 4/4] x86, efi: Map runtime services 1:1

Matt Fleming
2013-06-06T13:14:39Z

On Sun, 02 Jun, at 02:56:10PM, Borislav Petkov wrote:
> From: Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>
>
> Due to the braindead design of EFI, we cannot map runtime services more
> than once for the duration of a booted system. Thus, if we want to use
> EFI runtime services in a kexec'ed kernel, maybe the only possible and
> sensible approach would be to map them 1:1 so that when the kexec kernel
> loads, it can simply call those addresses without the need for remapping
> (which doesn't work anyway).
>
> Furthermore, this mapping approach could be of help with b0rked EFI
> implementations for a different set of reasons.
>
> This implementation is 64-bit only for now and it boots fine in kvm with
> OVMF BIOS.
>
> Signed-off-by: Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>
> ---
> arch/x86/include/asm/efi.h | 2 +
> arch/x86/platform/efi/efi.c | 161 +++++++++++++++++++++++++++++-------
> arch/x86/platform/efi/efi_stub_64.S | 48 +++++++++++
> 3 files changed, 180 insertions(+), 31 deletions(-)

This patch makes my TunnelMountain machine spin in handle_pte_fault()
when triggering one of the "firmware makes references to physical
addresses" code paths.

I'll try and dig into this tomorrow to figure out what's going on.

--
Matt Fleming, Intel Open Source Technology Center