From c58cf741795ad5df08dcc13d1d0ccd05a853b2a6 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Tue, 14 Mar 2017 10:15:17 +0000 Subject: [PATCH] KVM: MIPS: Update kvm_lose_fpu() for VZ MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Update the implementation of kvm_lose_fpu() for VZ, where there is no need to enable the FPU/MSA in the root context if the FPU/MSA state is loaded but disabled in the guest context. The trap & emulate implementation needs to disable FPU/MSA in the root context when the guest disables them in order to catch the COP1 unusable or MSA disabled exception when they're used and pass it on to the guest. For VZ however as long as the context is loaded and enabled in the root context, the guest can enable and disable it in the guest context without the hypervisor having to do much, and will take guest exceptions without hypervisor intervention if used without being enabled in the guest context. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org --- arch/mips/kvm/mips.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 15a1b1716c2e..a743f67378ba 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -1527,16 +1527,18 @@ void kvm_drop_fpu(struct kvm_vcpu *vcpu) void kvm_lose_fpu(struct kvm_vcpu *vcpu) { /* - * FPU & MSA get disabled in root context (hardware) when it is disabled - * in guest context (software), but the register state in the hardware - * may still be in use. This is why we explicitly re-enable the hardware - * before saving. + * With T&E, FPU & MSA get disabled in root context (hardware) when it + * is disabled in guest context (software), but the register state in + * the hardware may still be in use. + * This is why we explicitly re-enable the hardware before saving. */ preempt_disable(); if (cpu_has_msa && vcpu->arch.aux_inuse & KVM_MIPS_AUX_MSA) { - set_c0_config5(MIPS_CONF5_MSAEN); - enable_fpu_hazard(); + if (!IS_ENABLED(CONFIG_KVM_MIPS_VZ)) { + set_c0_config5(MIPS_CONF5_MSAEN); + enable_fpu_hazard(); + } __kvm_save_msa(&vcpu->arch); trace_kvm_aux(vcpu, KVM_TRACE_AUX_SAVE, KVM_TRACE_AUX_FPU_MSA); @@ -1549,8 +1551,10 @@ void kvm_lose_fpu(struct kvm_vcpu *vcpu) } vcpu->arch.aux_inuse &= ~(KVM_MIPS_AUX_FPU | KVM_MIPS_AUX_MSA); } else if (vcpu->arch.aux_inuse & KVM_MIPS_AUX_FPU) { - set_c0_status(ST0_CU1); - enable_fpu_hazard(); + if (!IS_ENABLED(CONFIG_KVM_MIPS_VZ)) { + set_c0_status(ST0_CU1); + enable_fpu_hazard(); + } __kvm_save_fpu(&vcpu->arch); vcpu->arch.aux_inuse &= ~KVM_MIPS_AUX_FPU; -- 2.20.1