From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH v7 01/15] nEPT: Support LOAD_IA32_EFER entry/exit controls for L1 Date: Mon, 5 Aug 2013 14:40:32 +0300 Message-ID: <20130805114032.GE10891@redhat.com> References: <1375690040-5764-1-git-send-email-gleb@redhat.com> <1375690040-5764-2-git-send-email-gleb@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm , Xiao Guangrong , Jun Nakajima , Yang Zhang , Paolo Bonzini To: Arthur Chunqi Li Return-path: Received: from mx1.redhat.com ([209.132.183.28]:17769 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751699Ab3HELkh (ORCPT ); Mon, 5 Aug 2013 07:40:37 -0400 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Aug 05, 2013 at 07:27:33PM +0800, Arthur Chunqi Li wrote: > On Mon, Aug 5, 2013 at 4:07 PM, Gleb Natapov wrote: > > From: Nadav Har'El > > > > Recent KVM, since http://kerneltrap.org/mailarchive/linux-kvm/2010/5/2/6261577 > > switch the EFER MSR when EPT is used and the host and guest have different > > NX bits. So if we add support for nested EPT (L1 guest using EPT to run L2) > > and want to be able to run recent KVM as L1, we need to allow L1 to use this > > EFER switching feature. > > > > To do this EFER switching, KVM uses VM_ENTRY/EXIT_LOAD_IA32_EFER if available, > > and if it isn't, it uses the generic VM_ENTRY/EXIT_MSR_LOAD. This patch adds > > support for the former (the latter is still unsupported). > > > > Nested entry and exit emulation (prepare_vmcs_02 and load_vmcs12_host_state, > > respectively) already handled VM_ENTRY/EXIT_LOAD_IA32_EFER correctly. So all > > that's left to do in this patch is to properly advertise this feature to L1. > > > > Note that vmcs12's VM_ENTRY/EXIT_LOAD_IA32_EFER are emulated by L0, by using > > vmx_set_efer (which itself sets one of several vmcs02 fields), so we always > > support this feature, regardless of whether the host supports it. > > > > Reviewed-by: Orit Wasserman > > Signed-off-by: Nadav Har'El > > Signed-off-by: Jun Nakajima > > Signed-off-by: Xinhao Xu > > Signed-off-by: Yang Zhang > > Signed-off-by: Gleb Natapov > > --- > > arch/x86/kvm/vmx.c | 23 ++++++++++++++++------- > > 1 file changed, 16 insertions(+), 7 deletions(-) > > > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > > index e999dc7..27efa6a 100644 > > --- a/arch/x86/kvm/vmx.c > > +++ b/arch/x86/kvm/vmx.c > > @@ -2198,7 +2198,8 @@ static __init void nested_vmx_setup_ctls_msrs(void) > > #else > > nested_vmx_exit_ctls_high = 0; > > #endif > > - nested_vmx_exit_ctls_high |= VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR; > > + nested_vmx_exit_ctls_high |= (VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR | > > + VM_EXIT_LOAD_IA32_EFER); > Gleb, why we don't need to check whether host supports > VM_EXIT_LOAD_IA32_EFER here, as what you noted in my > VM_EXIT_LOAD_IA32_PAT patch? Nested VMX completely emulates the capability. It calls vmx_set_efer() which suppose to handle hosts without VM_EXIT_LOAD_IA32_EFER support. -- Gleb.