From nobody Sat Feb 7 18:15:37 2026 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 417B542EECE for ; Fri, 6 Feb 2026 19:09:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770404994; cv=none; b=OeMw5uPwVRs+mO1aQL/b60Ki/Z6X1LbwDm/5BQVMKlvd1/H2yYszCqQs5w6Ate7IalkY58Lw+lh9k9U4KQ7pyq6NZq2stEA00bZY/bMj9BknmdSgBd1Md73yigcpYUzNs+4LT9yaxhUoQCZKoDhJOc6+rcyxN45j6wbmbJNiOCw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770404994; c=relaxed/simple; bh=YTcYKED/wvqngcm2f7lwHOcbYRZ3YkO3jVQI2neMGIQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I2+2nB7jBksTuEz0W0wra4hcLA5rhpyXZ/3OhN9SlQ2wAl53wwgwuHaXM9gn7GWATF8Phs1dl2CKpICchs+RtiRTFmCtS9eFZa/DU+yOoNReQwltdO0hWscReHfNvmVVoBkk4scS2kA2JuxuwMHOcCrCyN3eAW7DHlqpr508AS0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=taJ4FaJn; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="taJ4FaJn" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1770404992; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RK+d5ocqMQ7flxrKcmagDp5JVPOYd8dDWt+aOfINdHE=; b=taJ4FaJnhsdTtXwbeP7oPgjSfct0q4xMkHmi/QyP/1oYksNQ3BMdCEvUNgEFab1HgwEjrs 9IWaHHFORX47aM4TXl+sgWJD9NYH7VQ0T0KPu4MY/ShhWC7XzRJqMYBtwiSoFl49ybZEZx qs7kfAH2Rxaw5rg2OcLltsSfYEmLYmg= From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed , Jim Mattson Subject: [PATCH v5 26/26] KVM: nSVM: Only copy SVM_MISC_ENABLE_NP from VMCB01's misc_ctl Date: Fri, 6 Feb 2026 19:08:51 +0000 Message-ID: <20260206190851.860662-27-yosry.ahmed@linux.dev> In-Reply-To: <20260206190851.860662-1-yosry.ahmed@linux.dev> References: <20260206190851.860662-1-yosry.ahmed@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" The 'misc_ctl' field in VMCB02 is taken as-is from VMCB01. However, the only bit that needs to copied is SVM_MISC_ENABLE_NP, as all other known bits in misc_ctl are related to SEV guests, and KVM doesn't support nested virtualization for SEV guests. Only copy SVM_MISC_ENABLE_NP to harden against future bugs if/when other bits are set for L1 but should not be set for L2. Opportunistically add a comment explaining why SVM_MISC_ENABLE_NP is taken from VMCB01 and not VMCB02. Suggested-by: Jim Mattson Signed-off-by: Yosry Ahmed --- arch/x86/kvm/svm/nested.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index c87738962970..d80b1bde6630 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -852,8 +852,16 @@ static void nested_vmcb02_prepare_control(struct vcpu_= svm *svm, V_NMI_BLOCKING_MASK); } =20 - /* Copied from vmcb01. msrpm_base can be overwritten later. */ - vmcb02->control.misc_ctl =3D vmcb01->control.misc_ctl; + /* + * Copied from vmcb01. msrpm_base can be overwritten later. + * + * SVM_MISC_ENABLE_NP in vmcb12 is only used for consistency checks. If + * L1 enables NPTs, KVM shadows L1's NPTs and uses those to run L2. If + * L1 disables NPT, KVM runs L2 with the same NPTs used to run L1. For + * the latter, L1 runs L2 with shadow page tables that translate L2 GVAs + * to L1 GPAs, so the same NPTs can be used for L1 and L2. + */ + vmcb02->control.misc_ctl =3D vmcb01->control.misc_ctl & SVM_MISC_ENABLE_N= P; vmcb02->control.iopm_base_pa =3D vmcb01->control.iopm_base_pa; vmcb02->control.msrpm_base_pa =3D vmcb01->control.msrpm_base_pa; vmcb_mark_dirty(vmcb02, VMCB_PERM_MAP); --=20 2.53.0.rc2.204.g2597b5adb4-goog