On 15/01/18 19:39, James Morse wrote: > Non-VHE systems take an exception to EL2 in order to world-switch into the > guest. When returning from the guest KVM implicitly restores the DAIF > flags when it returns to the kernel at EL1. > > With VHE none of this exception-level jumping happens, so KVMs > world-switch code is exposed to the host kernel's DAIF values, and KVM > spills the guest-exit DAIF values back into the host kernel. > On entry to a guest we have Debug and SError exceptions unmasked, KVM > has switched VBAR but isn't prepared to handle these. On guest exit > Debug exceptions are left disabled once we return to the host and will > stay this way until we enter user space. > > Add a helper to mask/unmask DAIF around VHE guests. The unmask can only > happen after the hosts VBAR value has been synchronised by the isb in > __vhe_hyp_call (via kvm_call_hyp()). Masking could be as late as > setting KVMs VBAR value, but is kept here for symmetry. > > Signed-off-by: James Morse <james.morse@xxxxxxx> > Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx> M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
