From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (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 F1B9533D6E5 for ; Mon, 15 Dec 2025 19:30:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765827028; cv=none; b=TfTWMktrsG/dWlMns/gr7MLyZRfZuFjAz0eJOvfJAtQOEFwqf1dQRLcMHJj9DScpcuGnIn3g70lTsi70AMec3+sxIUXRFB/NAVanLIx8Vc2IMo2Q6lLrjA0Za06Myc37EBzMntmgtnISG0V7utn4uReZ+4SmsvUGmML/vzQxPYs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765827028; c=relaxed/simple; bh=TmAIHFIBy67IQq6UqFfKfKWIKkOc3mEymWWssMf11tk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EYURr1+g5fKMT/W2S0m7CjnmF2fYo39WdJEVf2sBMhNu+ssb5hZRVCl3A0VJfF2lDjU2Z3MguWbO2CEptkWTmkvY8BUH6xlnWMuRbTwM7qLL6KuR8qSetBa2P+6jbmg2fPOqTTQQd/p9X55j1VS1EBzPVF3iCdj5vLM28vzdkbs= 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=O0Wh4LLY; arc=none smtp.client-ip=91.218.175.183 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="O0Wh4LLY" 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=1765827020; 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=VWrJEh8Nktie/iD1iDW/0p+teecaOKksnLMwXSZBOC0=; b=O0Wh4LLYRNuUX2JJSHPF8u7dJGfrh96D37+8FCxCXMf9uFR73NfEapRADNP/mT8PqM5E4k PJydUXFPsw0KtOcuuIDo/HimCGD40DoCq8G70LazA09FJH0OKXLuAO+6aIsbpUSsJi6MCb Jb+z4ThEDnSRCHr15IR+NzLc/qO/ZrI= From: Yosry Ahmed To: Paolo Bonzini , Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed , Jim Mattson Subject: [PATCH v3 26/26] KVM: nSVM: Only copy NP_ENABLE from VMCB01's misc_ctl Date: Mon, 15 Dec 2025 19:27:21 +0000 Message-ID: <20251215192722.3654335-28-yosry.ahmed@linux.dev> In-Reply-To: <20251215192722.3654335-1-yosry.ahmed@linux.dev> References: <20251215192722.3654335-1-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, 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 NP_ENABLE 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 NP_ENABLE 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 2f1006119fe7..7af701e92c81 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -820,8 +820,16 @@ 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); -- 2.52.0.239.gd5f0c6e74e-goog