x86/efi: Fix kernel panic when CONFIG_DEBUG_VIRTUAL is enabled
authorSai Praneeth <sai.praneeth.prakhya@intel.com>
Fri, 16 Oct 2015 23:20:27 +0000 (16:20 -0700)
committerMatt Fleming <matt@codeblueprint.co.uk>
Sun, 25 Oct 2015 10:22:25 +0000 (10:22 +0000)
commit2c66e24d75d424919c42288b418d2e593fa818b1
tree97d12d3cdb2de8b7d17d0433e1d899cec965b271
parent0f96a99dab366333439e110d6ad253bc7c557c09
x86/efi: Fix kernel panic when CONFIG_DEBUG_VIRTUAL is enabled

When CONFIG_DEBUG_VIRTUAL is enabled, all accesses to __pa(address) are
monitored to see whether address falls in direct mapping or kernel text
mapping (see Documentation/x86/x86_64/mm.txt for details), if it does
not, the kernel panics. During 1:1 mapping of EFI runtime services we access
virtual addresses which are == physical addresses, thus the 1:1 mapping
and these addresses do not fall in either of the above two regions and
hence when passed as arguments to __pa() kernel panics as reported by
Dave Hansen here https://lkml.kernel.org/r/5462999A.7090706@intel.com.

So, before calling __pa() virtual addresses should be validated which
results in skipping call to split_page_count() and that should be fine
because it is used to keep track of everything *but* 1:1 mappings.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Reported-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Glenn P Williamson <glenn.p.williamson@intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
arch/x86/mm/pageattr.c