From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) (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 83E94340D8C for ; Mon, 10 Nov 2025 22:30:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762813807; cv=none; b=NuPHfrflkcg083rF8oXnqBoakG6MGirMLiBiKrchri0tGfx4sENgbY8jSfehUHnOCUZvN3tvJSvbIDk0K9LgHYCBk81BaRfhmy+a+MxcvIY6mwJgv8xxaLlNbcJjwGjWynpCcWB/sv/8yFUChADygTI7y/Uxw7d0HULekjWHb1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762813807; c=relaxed/simple; bh=cp97R3GdqDcm5NylaZccmJl3gy9Tx4+loyUIVJzusNM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=P7/5au0x2w0b+acqcyF9fSqNKe8PZ94qdpp9ccNjwmh0t9bIrhDZMz3gCNCkmje3wMa57z2fmUiLUj4Hc85y5hJ1kbladVLpYPFomoxAMj0olo13r+xJf+w0Auy9cjo1rP/GsyOy/yGeItLTzbzG2ojWIkN8gf5H47OTP6KDgKE= 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=CtLichXf; arc=none smtp.client-ip=91.218.175.171 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="CtLichXf" 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=1762813803; 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=LaX7+H5ws1ElWVssSHUHDq3sKJLlQwFG3aehtAQ6AmU=; b=CtLichXfu636fEu6ihIFPj85dXsPwIG87igdhtmaKtn4HEsdv3VJoDz8xSuOAUeWr+WUbK V+FIAJ9Jnp2J/ozVl8MalyTkVZFTP4v6demE4QVN9SogKudzwYvq4d3j5m5rjhHqtjnPkm ovAtlj52IaKooGM2el2ZgIU2cD3unXU= From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , Jim Mattson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v2 13/13] KVM: nSVM: Only copy NP_ENABLE from VMCB01's misc_ctl Date: Mon, 10 Nov 2025 22:29:22 +0000 Message-ID: <20251110222922.613224-14-yosry.ahmed@linux.dev> In-Reply-To: <20251110222922.613224-1-yosry.ahmed@linux.dev> References: <20251110222922.613224-1-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. 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 503cb7f5a4c5f..4e278c1f9e6b3 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -837,8 +837,16 @@ 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; -- 2.51.2.1041.gc1ab5b90ca-goog