Re: [PATCH v5 11/17] arm64: docs: document pointer authentication

[Jon Masters]

On 10/19/18 1:45 PM, Will Deacon wrote:

>>> I think an alternative solution is to just disable trapping of pointer
>>> auth instructions in KVM. This will mean that the instructions will
>>> behave the same in the guest as they do in the host. HINT-space
>>> instructions (including XPACLRI) will behave as NOPs (or perform their
>>> function, if enabled by the guest), and will not trap.
>>
>> OK, so this means disabling the trap (during early EL2 setup) but still
>> sanitizing the CPUID not to report the feature to EL1 unless fully
>> supported on all CPUs.
> 
> ... which is perfectly sensible, but not actually my main concern here.
> I'm worried about the possibility of distributions shipping *now* with
> userspace that's built with these instructions. That stuff is going to
> break if/when it encounters v8.3 hardware, and I don't think we can do
> much about it other than alert them to the potential issue.

FYI tracking this for RHEL. It's not a problem currently. I'll alert our
tools teams to hold off on any PAC work until this is figured out.

Jon.

-- 
Computer Architect | Sent with my Fedora powered laptop