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

[Peter Maydell]

On 18 February 2016 at 18:03, Catalin Marinas <catalin.marinas at arm.com> wrote:
> On Fri, Feb 05, 2016 at 02:58:45PM +0000, James Morse wrote:
>> 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...

thanks
-- PMM