Dave Hansen <dave.han...@linux.intel.com> wrote: > On 02/15/2018 08:35 AM, Nadav Amit wrote: >> I removed the PTI disabling while SMEP is unsupported, although I >> must admit I did not fully understand why it is required. > > Do you mean you don't fully understand how PTI gives SMEP-like behavior > on non-SMEP hardware?
No. I understand how it provide SMEP-like behavior, and I understand the value of SMEP by itself. However, I do not understand why SMEP-like protection is required to protect processes that run in compatibility-mode from Meltdown/Spectre attacks. As far as I understand, the process should not be able to manipulate the kernel to execute code in the low 4GB.
