From patchwork Thu Sep 26 21:43:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 11163381 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9033A76 for ; Thu, 26 Sep 2019 21:43:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77A51222C3 for ; Thu, 26 Sep 2019 21:43:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726394AbfIZVnJ (ORCPT ); Thu, 26 Sep 2019 17:43:09 -0400 Received: from mga07.intel.com ([134.134.136.100]:8270 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725943AbfIZVnF (ORCPT ); Thu, 26 Sep 2019 17:43:05 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Sep 2019 14:43:03 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,553,1559545200"; d="scan'208";a="192958528" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.41]) by orsmga003.jf.intel.com with ESMTP; 26 Sep 2019 14:43:03 -0700 From: Sean Christopherson To: Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Reto Buerki Subject: [PATCH 1/2] KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter Date: Thu, 26 Sep 2019 14:43:01 -0700 Message-Id: <20190926214302.21990-2-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190926214302.21990-1-sean.j.christopherson@intel.com> References: <20190926214302.21990-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Write the desired L2 CR3 into vmcs02.GUEST_CR3 during nested VM-Enter isntead of deferring the VMWRITE until vmx_set_cr3(). If the VMWRITE is deferred, then KVM can consume a stale vmcs02.GUEST_CR3 when it refreshes vmcs12->guest_cr3 during nested_vmx_vmexit() if the emulated VM-Exit occurs without actually entering L2, e.g. if the nested run is squashed because L2 is being put into HLT. In an ideal world where EPT *requires* unrestricted guest (and vice versa), VMX could handle CR3 similar to how it handles RSP and RIP, e.g. mark CR3 dirty and conditionally load it at vmx_vcpu_run(). But the unrestricted guest silliness complicates the dirty tracking logic to the point that explicitly handling vmcs02.GUEST_CR3 during nested VM-Enter is a simpler overall implementation. Cc: stable@vger.kernel.org Reported-by: Reto Buerki Signed-off-by: Sean Christopherson Reviewed-by: Liran Alon --- arch/x86/kvm/vmx/nested.c | 8 ++++++++ arch/x86/kvm/vmx/vmx.c | 9 ++++++--- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 41abc62c9a8a..971a24134081 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2418,6 +2418,14 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, entry_failure_code)) return -EINVAL; + /* + * Immediately write vmcs02.GUEST_CR3. It will be propagated to vmcs12 + * on nested VM-Exit, which can occur without actually running L2, e.g. + * if L2 is entering HLT state, and thus without hitting vmx_set_cr3(). + */ + if (enable_ept) + vmcs_writel(GUEST_CR3, vmcs12->guest_cr3); + /* Late preparation of GUEST_PDPTRs now that EFER and CRs are set. */ if (load_guest_pdptrs_vmcs12 && nested_cpu_has_ept(vmcs12) && is_pae_paging(vcpu)) { diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index d4575ffb3cec..b530950a9c2b 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2985,6 +2985,7 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) { struct kvm *kvm = vcpu->kvm; unsigned long guest_cr3; + bool skip_cr3 = false; u64 eptp; guest_cr3 = cr3; @@ -3000,15 +3001,17 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock); } - if (enable_unrestricted_guest || is_paging(vcpu) || - is_guest_mode(vcpu)) + if (is_guest_mode(vcpu)) + skip_cr3 = true; + else if (enable_unrestricted_guest || is_paging(vcpu)) guest_cr3 = kvm_read_cr3(vcpu); else guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr; ept_load_pdptrs(vcpu); } - vmcs_writel(GUEST_CR3, guest_cr3); + if (!skip_cr3) + vmcs_writel(GUEST_CR3, guest_cr3); } int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) From patchwork Thu Sep 26 21:43:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 11163379 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 37E9676 for ; Thu, 26 Sep 2019 21:43:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20A83222C3 for ; Thu, 26 Sep 2019 21:43:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726237AbfIZVnF (ORCPT ); Thu, 26 Sep 2019 17:43:05 -0400 Received: from mga07.intel.com ([134.134.136.100]:8270 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725955AbfIZVnE (ORCPT ); Thu, 26 Sep 2019 17:43:04 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Sep 2019 14:43:03 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,553,1559545200"; d="scan'208";a="192958531" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.41]) by orsmga003.jf.intel.com with ESMTP; 26 Sep 2019 14:43:03 -0700 From: Sean Christopherson To: Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Reto Buerki Subject: [PATCH 2/2] KVM: VMX: Skip GUEST_CR3 VMREAD+VMWRITE if the VMCS is up-to-date Date: Thu, 26 Sep 2019 14:43:02 -0700 Message-Id: <20190926214302.21990-3-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190926214302.21990-1-sean.j.christopherson@intel.com> References: <20190926214302.21990-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Skip the VMWRITE to update GUEST_CR3 if CR3 is not available, i.e. has not been read from the VMCS since the last VM-Enter. If vcpu->arch.cr3 is stale, kvm_read_cr3(vcpu) will refresh vcpu->arch.cr3 from the VMCS, meaning KVM will do a VMREAD and then VMWRITE the value it just pulled from the VMCS. Note, this is a purely theoretical change, no instances of skipping the VMREAD+VMWRITE have been observed with this change. Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/vmx.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index b530950a9c2b..6de09f60edf3 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3003,10 +3003,12 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) if (is_guest_mode(vcpu)) skip_cr3 = true; - else if (enable_unrestricted_guest || is_paging(vcpu)) - guest_cr3 = kvm_read_cr3(vcpu); - else + else if (!enable_unrestricted_guest && !is_paging(vcpu)) guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr; + else if (test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail)) + guest_cr3 = vcpu->arch.cr3; + else + skip_cr3 = true; /* vmcs01.GUEST_CR3 is up-to-date. */ ept_load_pdptrs(vcpu); }