Re: [PATCH] x86/efi: Setup separate EFI page tables in kexec paths

From: Srikar Dronamraju
Date: Thu Jan 21 2016 - 14:34:44 EST

* Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> [2016-01-21 14:11:59]:

> The switch to using a new dedicated page table for EFI runtime calls
> in commit commit 67a9108ed431 ("x86/efi: Build our own page table
> structures") failed to take into account changes required for the
> kexec code paths, which are unfortunately duplicated in the EFI code.
> Call the allocation and setup functions in kexec_enter_virtual_mode()
> just like we do for __efi_enter_virtual_mode() to avoid hitting
> NULL-pointer dereferences when making EFI runtime calls.
> At the very least, the call to efi_setup_page_tables() should have
> existed for kexec before commit 67a9108ed431. Things just magically
> worked because we were actually using the kernel's page tables that
> contained the required mappings.
> Reported-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> Cc: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
> Cc: Dave Young <dyoung@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Signed-off-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>

Applied this patch on top of tip/x86/efi and was able to build and boot
the kernel.

Thanks and Regards
Srikar Dronamraju