From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 2/5] KVM: x86: drop fpu_activate hook Date: Mon, 18 Aug 2014 13:26:41 +0300 Message-ID: <53F1D4E1.7@gmail.com> References: <1408355431-115633-1-git-send-email-wanpeng.li@linux.intel.com> <1408355431-115633-2-git-send-email-wanpeng.li@linux.intel.com> <53F1D36C.8070606@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Paolo Bonzini , Wanpeng Li Return-path: In-Reply-To: <53F1D36C.8070606@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 08/18/2014 01:20 PM, Paolo Bonzini wrote: > Il 18/08/2014 11:50, Wanpeng Li ha scritto: >> fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on >> clts), however, there is no user currently, this patch drop it. >> >> Reviewed-by: Yang Zhang >> Signed-off-by: Wanpeng Li >> --- >> arch/x86/include/asm/kvm_host.h | 1 - >> arch/x86/kvm/svm.c | 1 - >> arch/x86/kvm/vmx.c | 1 - >> 3 files changed, 3 deletions(-) >> >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> index 5724601..b68f3e5 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -710,7 +710,6 @@ struct kvm_x86_ops { >> void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg); >> unsigned long (*get_rflags)(struct kvm_vcpu *vcpu); >> void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags); >> - void (*fpu_activate)(struct kvm_vcpu *vcpu); >> void (*fpu_deactivate)(struct kvm_vcpu *vcpu); >> >> void (*tlb_flush)(struct kvm_vcpu *vcpu); >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index ddf7427..1f49c86 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -4349,7 +4349,6 @@ static struct kvm_x86_ops svm_x86_ops = { >> .cache_reg = svm_cache_reg, >> .get_rflags = svm_get_rflags, >> .set_rflags = svm_set_rflags, >> - .fpu_activate = svm_fpu_activate, >> .fpu_deactivate = svm_fpu_deactivate, >> >> .tlb_flush = svm_flush_tlb, >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 71cbee5..2963303 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -8896,7 +8896,6 @@ static struct kvm_x86_ops vmx_x86_ops = { >> .cache_reg = vmx_cache_reg, >> .get_rflags = vmx_get_rflags, >> .set_rflags = vmx_set_rflags, >> - .fpu_activate = vmx_fpu_activate, >> .fpu_deactivate = vmx_fpu_deactivate, >> >> .tlb_flush = vmx_flush_tlb, >> > Avi/Gleb, do you remember any particular reason for this? > IIRC (vaguely) if we expect the fpu to be used in the near future, we activate it eagerly so that we don't fault when it is used. Prevents the sequence: guest user: use fpu #NM host: reflect #NM to guest guest kernel: CLTS guest kernel: switch fpu state #NM host: switch fpu guest kernel: switch fpu state (restarted) guest user: use fpu (restarted) Why was the user removed? Full-time eager fpu?