Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751644AbdHQFLV (ORCPT ); Thu, 17 Aug 2017 01:11:21 -0400 Received: from mga06.intel.com ([134.134.136.31]:42139 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751585AbdHQFLS (ORCPT ); Thu, 17 Aug 2017 01:11:18 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,386,1498546800"; d="scan'208";a="1206626420" Subject: Re: [PATCH] KVM/VMX: Avoid CR3 VMEXIT during guest real mode when "unrestricted guest" is supported. To: Paolo Bonzini References: <1502848704-7474-1-git-send-email-tianyu.lan@intel.com> <1cf50aea-0c1c-f2f1-952e-9bcdd76722e8@redhat.com> Cc: rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org From: Lan Tianyu Message-ID: Date: Thu, 17 Aug 2017 13:08:21 +0800 User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <1cf50aea-0c1c-f2f1-952e-9bcdd76722e8@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2662 Lines: 72 On 2017年08月16日 17:25, Paolo Bonzini wrote: > On 16/08/2017 03:58, Lan Tianyu wrote: >> These CR3 VMEXITs was introduced for platform without "unrestricted guest" >> support. This is to set ept identity table to guest CR3 in guest real >> mode because these platforms don't support ept real mode(CR0.PE and CR0.PG >> must be set to 1). But these VMEXITs is redundant for platforms with >> "unrestricted guest" support. > > This is true, but I'm not sure it's a good idea to make things more > complex... It is working code and is not a bottleneck anywhere. Yes, this is just code clear up and will not affect function. I thought this change was missed when introduced unrestricted guest support. -- Best regards Tianyu Lan > > Paolo > >> Signed-off-by: Lan Tianyu >> --- >> arch/x86/kvm/vmx.c | 22 +++++++++++++--------- >> 1 file changed, 13 insertions(+), 9 deletions(-) >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 9b21b12..46dcf50 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -4221,18 +4221,20 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0, >> vmx_decache_cr3(vcpu); >> if (!(cr0 & X86_CR0_PG)) { >> /* From paging/starting to nonpaging */ >> - vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, >> - vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) | >> - (CPU_BASED_CR3_LOAD_EXITING | >> - CPU_BASED_CR3_STORE_EXITING)); >> + if (!enable_unrestricted_guest) >> + vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, >> + vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) | >> + (CPU_BASED_CR3_LOAD_EXITING | >> + CPU_BASED_CR3_STORE_EXITING)); >> vcpu->arch.cr0 = cr0; >> vmx_set_cr4(vcpu, kvm_read_cr4(vcpu)); >> } else if (!is_paging(vcpu)) { >> /* From nonpaging to paging */ >> - vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, >> - vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) & >> - ~(CPU_BASED_CR3_LOAD_EXITING | >> - CPU_BASED_CR3_STORE_EXITING)); >> + if (!enable_unrestricted_guest) >> + vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, >> + vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) & >> + ~(CPU_BASED_CR3_LOAD_EXITING | >> + CPU_BASED_CR3_STORE_EXITING)); >> vcpu->arch.cr0 = cr0; >> vmx_set_cr4(vcpu, kvm_read_cr4(vcpu)); >> } >> @@ -4311,7 +4313,9 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) >> } >> >> vmx_flush_tlb(vcpu); >> - vmcs_writel(GUEST_CR3, guest_cr3); >> + >> + if (!enable_unrestricted_guest || !enable_ept) >> + vmcs_writel(GUEST_CR3, guest_cr3); >> } >> >> static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) >> >