On Thu, Jun 11, 2020 at 10:38:48AM -0700, Sean Christopherson wrote: > Isn't it possible for the #VC handler to hit a #PF, e.g. on copy_from_user() > in insn_fetch_from_user()? If that happens, what prevents the #PF handler > from hitting a #VC? AIUI, do_vmm_communication() panics if the backup GHCB > is already in use, e.g. #VC->#PF->#VC->NMI->#VC would be fatal. This would be possible, if the #PF handler is able to trigger a #VC. But I am not sure how it could, except when it has to call printk. If #PF can trigger a #VC, then a fix is to further limit the time the GHCB is active, and make sure there are not faults of any kind when it actually is active. Then the only vector to care about is NMI. I will look into that. Regards, Joerg
