From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (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 6BA33302767 for ; Tue, 4 Nov 2025 20:00:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762286428; cv=none; b=lT81wvqBmcrM+fAo9BBmvYDc9qQtLc+vu7l5aOwpCyxhXxg7klgOLySka3CNw3eMSwQtB6Mdm7RyQMb+iOIT6Bg7Ic549KsfEXoUIRICooL7hddh8kvwkBf2mSwY2VZB48zILQQN2IhdDUG3OICAseqG/Ouodfoway50Mk42lwA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762286428; c=relaxed/simple; bh=EcgIhoJJP/s77cHSglnPoKdccWLA4uvOMrJzEbgg9sg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N45tfQiK1ZOZqiiL852Os4On7NnSNYxL5y4GyWJ6MhSlMSNb7tW7LDUp+2z+A1qSBEpMgDu2/oyfaWfn9dq40yLEuL5NV3rgOMZX8QPE73Gn71MS37GnuNRk9d7qG3bUdcShJK0yga/Yhas0MeTOjG+Dxh5SKl5gFxoLCgavjQw= 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=a/CRIOIF; arc=none smtp.client-ip=91.218.175.188 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="a/CRIOIF" 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=1762286424; 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=WjJ9YRNXaKKMg1wAlHxjNe5KXoC9eITnLkE0v1TW1y8=; b=a/CRIOIFznMb2Bs0qFJvKNoImNa97DniwO8CpeBBfDJM1XM2sAlS4awJ/WCUdJZzpaqGdB rav9nd+z9XPvq/5aUFU+n4grq6MwzZC3bHfKBpZtQhTEpj7YDpuP17cjEDpS8AS2GROpeL z8ZfTfTTHPevkDfFyIivso36GPMvsHQ= From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , Jim Mattson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH 11/11] KVM: nSVM: Only copy NP_ENABLE from VMCB01's nested_ctl Date: Tue, 4 Nov 2025 19:59:49 +0000 Message-ID: <20251104195949.3528411-12-yosry.ahmed@linux.dev> In-Reply-To: <20251104195949.3528411-1-yosry.ahmed@linux.dev> References: <20251104195949.3528411-1-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: 8bit X-Migadu-Flow: FLOW_OUT The 'misc_ctl' field in VMCB02 is taken as-is from VMCB01. However, the only bit that needs to copied is NP_ENABLE. This is a nop now because other bits are for SEV guests, which do not support nested. Nonetheless, this hardens against future bugs if/when other bits are set for L1 but should not be set for L2. 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 a223887e5b78d..81d8b10e26cdf 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -821,8 +821,16 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm, V_NMI_BLOCKING_MASK); } - /* Copied from vmcb01. msrpm_base can be overwritten later. */ - vmcb02->control.misc_ctl = vmcb01->control.misc_ctl; + /* + * Copied from vmcb01. msrpm_base can be overwritten later. + * + * NP_ENABLE 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 = vmcb01->control.misc_ctl & SVM_MISC_CTL_NP_ENABLE; vmcb02->control.iopm_base_pa = vmcb01->control.iopm_base_pa; vmcb02->control.msrpm_base_pa = vmcb01->control.msrpm_base_pa; vmcb_mark_dirty(vmcb02, VMCB_PERM_MAP); -- 2.51.2.1026.g39e6a42477-goog