On Fri, Nov 11, 2016 at 04:44:43PM -0800, Florian Fainelli wrote:

When CONFIG_DEBUG_VM is turned on, virt_to_phys() maps to
debug_virt_to_phys() which helps catch vmalloc space addresses being
passed. This is helpful in debugging bogus drivers that just assume
linear mappings all over the place.

For ARM, ARM64, Unicore32 and Microblaze, the architectures define
__virt_to_phys() as being the functional implementation of the address
translation, so we special case the debug stub to call into
__virt_to_phys directly.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 arch/arm/include/asm/memory.h      |  4 ++++
 arch/arm64/include/asm/memory.h    |  4 ++++
 include/asm-generic/memory_model.h |  4 ++++
 mm/debug.c                         | 15 +++++++++++++++
 4 files changed, 27 insertions(+)

What's the interaction between this and the DEBUG_VIRTUAL patches from Laura?

http://lkml.kernel.org/r/20161102210054.16621-7-labbott at redhat.com

They seem to be tackling the exact same problem afaict.

Will