From 96e6d03af66eaf3c83b3c5795a97a66a7cb74aad Mon Sep 17 00:00:00 2001
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date: Thu, 19 Apr 2018 12:34:05 +0530
Subject: [PATCH 6/9] powerpc64/ftrace: Disable ftrace during kvm entry/exit
References: bsc#1088804
Patch-mainline: v4.18-rc1
Git-commit: a4bc64d305af40446d0ac792bb8a9b2cd20af3d3
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 <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kvm/book3s_hv.c | 4 ++++
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 3 +++
2 files changed, 7 insertions(+)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 8c5286cc7490..78ca762e79d7 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2896,8 +2896,12 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
srcu_idx = srcu_read_lock(&vc->kvm->srcu);
+ this_cpu_disable_ftrace();
+
trap = __kvmppc_vcore_entry();
+ this_cpu_enable_ftrace();
+
srcu_read_unlock(&vc->kvm->srcu, srcu_idx);
trace_hardirqs_off();
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 57676e366937..6f3500c0f611 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -344,6 +344,9 @@ 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)
--
2.13.6