• Naveen N. Rao's avatar
    powerpc64/ftrace: Disable ftrace during kvm entry/exit · a4bc64d3
    Naveen N. Rao authored
    During guest entry/exit, we switch over to/from the guest MMU context
    and we cannot take exceptions in the hypervisor code.
    
    Since ftrace may be enabled and since it can result in us taking a trap,
    disable ftrace by setting paca->ftrace_enabled to zero. There are two
    paths through which we enter/exit a guest:
    1. If we are the vcore runner, then we enter the guest via
    __kvmppc_vcore_entry() and we disable ftrace around this. This is always
    the case for Power9, and for the primary thread on Power8.
    2. If we are a secondary thread in Power8, then we would be in nap due
    to SMT being disabled. We are woken up by an IPI to enter the guest. In
    this scenario, we enter the guest through kvm_start_guest(). We disable
    ftrace at this point. In this scenario, ftrace would only get re-enabled
    on the secondary thread when SMT is re-enabled (via start_secondary()).
    Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    a4bc64d3
book3s_hv_rmhandlers.S 88.3 KB