From mboxrd@z Thu Jan 1 00:00:00 1970 From: Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: [PATCH] KVM: nVMX: mask unrestricted_guest if disabled on L0 Date: Tue, 24 Feb 2015 17:30:06 +0100 Message-ID: <20150224163005.GB2186@potion.brq.redhat.com> References: <20150219160221.GB19057@potion.brq.redhat.com> <20150219211011.GE28728@tesla.redhat.com> <20150219222832.GA22611@tesla.redhat.com> <20150220161415.GA22152@potion.brq.redhat.com> <20150220194509.GD30563@tesla.home> <20150222154622.GA30296@tesla.redhat.com> <20150223135611.GB2102@potion.brq.redhat.com> <20150223161437.GI30296@tesla.redhat.com> <20150223170906.GA1055@tesla.redhat.com> <20150223180527.GK30296@tesla.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Paolo Bonzini , Jan Kiszka , kvm@vger.kernel.org, dgilbert@redhat.com, bsd@redhat.com, mtosatti@redhat.com To: Kashyap Chamarthy Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59835 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753048AbbBXQaV (ORCPT ); Tue, 24 Feb 2015 11:30:21 -0500 Content-Disposition: inline In-Reply-To: <20150223180527.GK30296@tesla.redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 2015-02-23 19:05+0100, Kashyap Chamarthy: > Tested with the _correct_ Kernel[1] (that has Radim's patch) now -- > applied it on both L0 and L1. >=20 > Result: Same as before -- Booting L2 causes L1 to reboot. However, th= e > stack trace from `dmesg` on L0 is took slightly different pat= h than > before -- it's using MSR handling: Thanks, the problem was deeper ... L1 enabled unrestricted mode while L= 0 had it disabled. L1 could then vmrun a L2 state that L0 would have to emulate, but that doesn't work. There are at least these solutions: 1) don't expose unrestricted_guest when L0 doesn't have it 2) fix unrestricted mode emulation code 3) handle the failure a without killing L1 I'd do just (1) -- emulating unrestricted mode is a loss. I have done initial testing and at least qemu-sanity-check works now: ---8<--- If EPT was enabled, unrestricted_guest was allowed in L1 regardless of L0. L1 triple faulted when running L2 guest that required emulation. Another side effect was 'WARN_ON_ONCE(vmx->nested.nested_run_pending)' in L0's dmesg: WARNING: CPU: 0 PID: 0 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0= x96e/0xb00 [kvm_intel] () Prevent this scenario by masking SECONDARY_EXEC_UNRESTRICTED_GUEST when the host doesn't have it enabled. =46ixes: 78051e3b7e35 ("KVM: nVMX: Disable unrestricted mode if ept=3D0= ") Signed-off-by: Radim Kr=C4=8Dm=C3=A1=C5=99 --- arch/x86/kvm/vmx.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index f7b20b417a3a..dbabea21357b 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2476,8 +2476,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcp= u_vmx *vmx) if (enable_ept) { /* nested EPT: emulate EPT also to L1 */ vmx->nested.nested_vmx_secondary_ctls_high |=3D - SECONDARY_EXEC_ENABLE_EPT | - SECONDARY_EXEC_UNRESTRICTED_GUEST; + SECONDARY_EXEC_ENABLE_EPT; vmx->nested.nested_vmx_ept_caps =3D VMX_EPT_PAGE_WALK_4_BIT | VMX_EPTP_WB_BIT | VMX_EPT_2MB_PAGE_BIT | VMX_EPT_INVEPT_BIT; @@ -2491,6 +2490,10 @@ static void nested_vmx_setup_ctls_msrs(struct vc= pu_vmx *vmx) } else vmx->nested.nested_vmx_ept_caps =3D 0; =20 + if (enable_unrestricted_guest) + vmx->nested.nested_vmx_secondary_ctls_high |=3D + SECONDARY_EXEC_UNRESTRICTED_GUEST; + /* miscellaneous data */ rdmsr(MSR_IA32_VMX_MISC, vmx->nested.nested_vmx_misc_low,