From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v7 01/15] nEPT: Support LOAD_IA32_EFER entry/exit controls for L1 Date: Tue, 06 Aug 2013 09:47:23 +0200 Message-ID: <5200AA0B.5080409@web.de> References: <1375690040-5764-1-git-send-email-gleb@redhat.com> <1375690040-5764-2-git-send-email-gleb@redhat.com> <20130805114032.GE10891@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="BfaJ0CEWFJ4xjr18T8FagtkQ1MDbuKLlj" Cc: Arthur Chunqi Li , kvm , Xiao Guangrong , Jun Nakajima , Yang Zhang , Paolo Bonzini To: Gleb Natapov Return-path: Received: from mout.web.de ([212.227.17.12]:57555 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751114Ab3HFHra (ORCPT ); Tue, 6 Aug 2013 03:47:30 -0400 Received: from mchn199C.mchp.siemens.de ([95.157.58.223]) by smtp.web.de (mrweb002) with ESMTPSA (Nemesis) id 0M7sga-1W1l0i2IN6-00vRCL for ; Tue, 06 Aug 2013 09:47:29 +0200 In-Reply-To: <20130805114032.GE10891@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --BfaJ0CEWFJ4xjr18T8FagtkQ1MDbuKLlj Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2013-08-05 13:40, Gleb Natapov wrote: > 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 diff= erent >>> NX bits. So if we add support for nested EPT (L1 guest using EPT to r= un L2) >>> and want to be able to run recent KVM as L1, we need to allow L1 to u= se this >>> EFER switching feature. >>> >>> To do this EFER switching, KVM uses VM_ENTRY/EXIT_LOAD_IA32_EFER if a= vailable, >>> and if it isn't, it uses the generic VM_ENTRY/EXIT_MSR_LOAD. This pat= ch 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, b= y 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(v= oid) >>> #else >>> nested_vmx_exit_ctls_high =3D 0; >>> #endif >>> - nested_vmx_exit_ctls_high |=3D VM_EXIT_ALWAYSON_WITHOUT_TRUE_= MSR; >>> + nested_vmx_exit_ctls_high |=3D (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. No, it doesn't. The values for host/guest are handled over via the corresponding VMCS fields, physically, even though the actual loading is emulated then. So we must not expose this feature unconditionally. That's the same pattern as with PAT, Arthur is right. I've a patch on top of v7 to fix this (and also the incorrect VM_ENTRY_IA32E_MODE reporting on 32-bit). Will post it soon as part of an updated version of my unrestricted guest mode series. Jan --BfaJ0CEWFJ4xjr18T8FagtkQ1MDbuKLlj Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlIAqg8ACgkQitSsb3rl5xQYmwCgwcQJzRt7u74cXfyxEYA8N5XJ XmYAnjtn4DvvluNd5EQqxEwV0IOJ+kTj =N7qK -----END PGP SIGNATURE----- --BfaJ0CEWFJ4xjr18T8FagtkQ1MDbuKLlj--