> Dave Hansen <dave.han...@intel.com> wrote: >> On 01/04/2018 08:51 PM, Andy Lutomirski wrote: >> > Do we need an arch_prctl() to enable IBRS for user mode? >> >> Eventually, once the dust settles. I think there's a spectrum of >> paranoia here, that is roughly (with increasing paranoia): >> >> 1. do nothing >> 2. do retpoline >> 3. do IBRS in kernel >> 4. do IBRS always >> >> I think you're asking for ~3.5. >> >> Patches for 1-3 are out there and 4 is pretty straightforward. Doing a >> arch_prctl() is still straightforward, but will be a much more niche >> thing than any of the other choices. Plus, with a user interface, we >> have to argue over the ABI for at least a month or two. ;)
I was chatting to Andrea about this, and we came to the conclusion one use might be for qemu; I was worried about (theoretically) whether userspace in a guest could read privileged data from the guest kernel by attacking the qemu process rather than by attacking the kernels. Dave -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
