From nobody Fri Sep 5 20:13:43 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9EE1BC32772 for ; Tue, 23 Aug 2022 11:08:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357061AbiHWLIK (ORCPT ); Tue, 23 Aug 2022 07:08:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357209AbiHWLGT (ORCPT ); Tue, 23 Aug 2022 07:06:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90370B516C; Tue, 23 Aug 2022 02:15:45 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D5D1961183; Tue, 23 Aug 2022 09:15:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D69E5C433C1; Tue, 23 Aug 2022 09:15:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661246133; bh=zUKg06zh818Ca6lgrCTltvZCNiOxsKkS5v4EFO6nHSg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qPWsiOTOJ7QVOe49koMYLmX8jpF0RKftvlVuz6ZDVFRi665yZ53Fhs/hvQVHd6jds zZtj0CQ9QT3N3f1nn/sgEbMoaHX7hl1lxgWVMDx+rw7MzFC3Gz3hcXaK4CAyPOaiYE FSqqr+Af2xPFZQnzxajjUoclhp/8bMbiIkvIb0zo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lei Wang , Sean Christopherson , Paolo Bonzini Subject: [PATCH 5.4 012/389] KVM: nVMX: Snapshot pre-VM-Enter BNDCFGS for !nested_run_pending case Date: Tue, 23 Aug 2022 10:21:30 +0200 Message-Id: <20220823080116.183989866@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080115.331990024@linuxfoundation.org> References: <20220823080115.331990024@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Sean Christopherson commit fa578398a0ba2c079fa1170da21fa5baae0cedb2 upstream. If a nested run isn't pending, snapshot vmcs01.GUEST_BNDCFGS irrespective of whether or not VM_ENTRY_LOAD_BNDCFGS is set in vmcs12. When restoring nested state, e.g. after migration, without a nested run pending, prepare_vmcs02() will propagate nested.vmcs01_guest_bndcfgs to vmcs02, i.e. will load garbage/zeros into vmcs02.GUEST_BNDCFGS. If userspace restores nested state before MSRs, then loading garbage is a non-issue as loading BNDCFGS will also update vmcs02. But if usersepace restores MSRs first, then KVM is responsible for propagating L2's value, which is actually thrown into vmcs01, into vmcs02. Restoring L2 MSRs into vmcs01, i.e. loading all MSRs before nested state is all kinds of bizarre and ideally would not be supported. Sadly, some VMMs do exactly that and rely on KVM to make things work. Note, there's still a lurking SMM bug, as propagating vmcs01.GUEST_BNDFGS to vmcs02 across RSM may corrupt L2's BNDCFGS. But KVM's entire VMX+SMM emulation is flawed as SMI+RSM should not toouch _any_ VMCS when use the "default treatment of SMIs", i.e. when not using an SMI Transfer Monitor. Link: https://lore.kernel.org/all/Yobt1XwOfb5M6Dfa@google.com Fixes: 62cf9bd8118c ("KVM: nVMX: Fix emulation of VM_ENTRY_LOAD_BNDCFGS") Cc: stable@vger.kernel.org Cc: Lei Wang Signed-off-by: Sean Christopherson Message-Id: <20220614215831.3762138-2-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/vmx/nested.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3068,7 +3068,8 @@ enum nvmx_vmentry_status nested_vmx_ente if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS)) vmx->nested.vmcs01_debugctl =3D vmcs_read64(GUEST_IA32_DEBUGCTL); if (kvm_mpx_supported() && - !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)) + (!vmx->nested.nested_run_pending || + !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))) vmx->nested.vmcs01_guest_bndcfgs =3D vmcs_read64(GUEST_BNDCFGS); =20 /*