[RFC PATCH] arm64/efi: use stable virtual mappings for UEFI runtime services

[Dave Young]

Hi, Geoff

On 10/13/14 at 03:52pm, Geoff Levand wrote:
> Hi Ard,
> 
> On Wed, 2014-10-08 at 19:38 +0200, Ard Biesheuvel wrote:
> > I haven't tested this code under kexec myself, but I have confirmed that
> > the runtime services work as expected (rtc-efi and efivars). The comments
> > that Mark Salter and Will Deacon gave on the id mapping patch here
> 
> I applied this patch to my kexec master branch [1] and tested a basic
> kexec re-boot using the FVP_Base_AEMv8A-AEMv8A_0.8_5602 model and the
> 14.09 LEG EFI build.
> 
> It crashes when the 2nd stage kernel is starting up on the first
> dereference of the c16 variable in uefi_init():
> 
>   c16 = early_memremap(efi.systab->fw_vendor, sizeof(vendor));
>   if (c16) {
>     for (i = 0; i < (int) sizeof(vendor) - 1 && *c16; ++i) {
>                                                 ^^^^ crashes here
> 
> early_memremap() returns 0xFFFFFFBFFBCBF618, and the dereference
> starts the crash.  I did not look into it further.

This is an expected behaviour as I mentioned before, we need save fw_vendor
and the other two physical addresses and pass them to 2nd kernel.

UEFI firmware will convert them to virtual address after entering virtual mode.

Thanks
Dave