[PATCH v2 0/5] arm64: kernel: Add support for User Access Override

On Fri, Feb 19, 2016 at 03:38:44PM +0000, Peter Maydell wrote:

On 18 February 2016 at 18:03, Catalin Marinas [off-list ref] wrote:

quoted

On Fri, Feb 05, 2016 at 02:58:45PM +0000, James Morse wrote:

quoted

James Morse (5):
  arm64: cpufeature: Change read_cpuid() to use sysreg's mrs_s macro
  arm64: add ARMv8.2 id_aa64mmfr2 boiler plate
  arm64: kernel: Add support for User Access Override
  arm64: cpufeature: Test 'matches' pointer to find the end of the list
  arm64: kernel: Don't toggle PAN on systems with UAO

Patches applied with an additional fixup on top for removing
get_thread_info().

Just to let you know, unfortunately this series breaks booting the
kernel on QEMU. We didn't implement the parts of the ID register
space that the ARM ARM documents as "reserved, RAZ", and so when
the kernel touches ID_AA64MMFR2 (new in v8.2) QEMU hands it an
UNDEF. This is obviously a bug in QEMU, and I just sent out a patch
for it: http://patchwork.ozlabs.org/patch/585237/ -- but of course
that doesn't do anything for all the buggy QEMUs already in the field.

This is more of a heads-up than a demand that you Do Something,
but perhaps somebody has a clever idea...

Only if Qemu had its own MIDR/REVIDR ;) (and patch the instruction like
other errata workarounds).

-- 
Catalin