From a4bc64d305af40446d0ac792bb8a9b2cd20af3d3 Mon Sep 17 00:00:00 2001 From: "Naveen N. Rao" Date: Thu, 19 Apr 2018 12:34:05 +0530 Subject: powerpc64/ftrace: Disable ftrace during kvm entry/exit 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: Naveen N. Rao Signed-off-by: Michael Ellerman --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/powerpc/kvm/book3s_hv_rmhandlers.S') diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index bd63fa8a08b5..2c3cbe0067b2 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -342,6 +342,9 @@ kvm_start_guest: ld r2,PACATOC(r13) + li r0,0 + stb r0,PACA_FTRACE_ENABLED(r13) + li r0,KVM_HWTHREAD_IN_KVM stb r0,HSTATE_HWTHREAD_STATE(r13) -- cgit v1.2.3-59-g8ed1b