Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752018AbdHPJZK (ORCPT ); Wed, 16 Aug 2017 05:25:10 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36127 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751843AbdHPJZI (ORCPT ); Wed, 16 Aug 2017 05:25:08 -0400 Subject: Re: [PATCH] KVM/VMX: Avoid CR3 VMEXIT during guest real mode when "unrestricted guest" is supported. To: Lan Tianyu 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 References: <1502848704-7474-1-git-send-email-tianyu.lan@intel.com> From: Paolo Bonzini Message-ID: <1cf50aea-0c1c-f2f1-952e-9bcdd76722e8@redhat.com> Date: Wed, 16 Aug 2017 11:25:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <1502848704-7474-1-git-send-email-tianyu.lan@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2373 Lines: 62 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. 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) >