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
