From 88b02cf97bb7e742db3e31671d54177e3e19fd89 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Thu, 15 Sep 2016 13:42:52 +1000 Subject: KVM: PPC: Book3S: Treat VTB as a per-subcore register, not per-thread POWER8 has one virtual timebase (VTB) register per subcore, not one per CPU thread. The HV KVM code currently treats VTB as a per-thread register, which can lead to spurious soft lockup messages from guests which use the VTB as the time source for the soft lockup detector. (CPUs before POWER8 did not have the VTB register.) For HV KVM, this fixes the problem by making only the primary thread in each virtual core save and restore the VTB value. With this, the VTB state becomes part of the kvmppc_vcore structure. This also means that "piggybacking" of multiple virtual cores onto one subcore is not possible on POWER8, because then the virtual cores would share a single VTB register. PR KVM emulates a VTB register, which is per-vcpu because PR KVM has no notion of CPU threads or SMT. For PR KVM we move the VTB state into the kvmppc_vcpu_book3s struct. Cc: stable@vger.kernel.org # v3.14+ Reported-by: Thomas Huth Tested-by: Thomas Huth Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s.c | 6 ------ 1 file changed, 6 deletions(-) (limited to 'arch/powerpc/kvm/book3s.c') diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c index ba231a1d43d4..b6952dd23152 100644 --- a/arch/powerpc/kvm/book3s.c +++ b/arch/powerpc/kvm/book3s.c @@ -599,9 +599,6 @@ int kvmppc_get_one_reg(struct kvm_vcpu *vcpu, u64 id, case KVM_REG_PPC_BESCR: *val = get_reg_val(id, vcpu->arch.bescr); break; - case KVM_REG_PPC_VTB: - *val = get_reg_val(id, vcpu->arch.vtb); - break; case KVM_REG_PPC_IC: *val = get_reg_val(id, vcpu->arch.ic); break; @@ -673,9 +670,6 @@ int kvmppc_set_one_reg(struct kvm_vcpu *vcpu, u64 id, case KVM_REG_PPC_BESCR: vcpu->arch.bescr = set_reg_val(id, *val); break; - case KVM_REG_PPC_VTB: - vcpu->arch.vtb = set_reg_val(id, *val); - break; case KVM_REG_PPC_IC: vcpu->arch.ic = set_reg_val(id, *val); break; -- cgit v1.2.3