From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f70.google.com (mail-pj1-f70.google.com [209.85.216.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 07F0D503BDB for ; Fri, 18 Sep 2026 15:45:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789746356; cv=none; b=PSoB/Ry8haeqlrWG9kf5yrQtsl7X/+j/+zfX/xN8d7jvCaUcuW3dE6TtfZ6px6KGC7RVZNPTGbASkaavWhkYJXLRn7FMAoSWKB77B9NRvPKVVNS+SkQn5uonazsCxy2ghtNuyKGvRZVKRBvlIRkAsRpyI0z0s0Tk9J+kxyUcGdA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789746356; c=relaxed/simple; bh=YBhMRCjXhrl0x9ETkgVjR+gi41jvBCooiZhKb3nRmV4=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=kv0+50rS+BIZFXE1wJqtpRQi926nAdvtChnq0RPy5ojbFCaOgrt+S8YKBb8xEn6EpnJSExzhiH98c/hV4SE+36KJuxjE8eq50KbDoUW5suk1sAPtd7DeBR0w8xaE6AuFtMu0HryXrGs+ElEecyt3akl1ap4d6Y8wWzMhBw+QCYM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jmattson.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=QK+rpOZX; arc=none smtp.client-ip=209.85.216.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jmattson.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QK+rpOZX" Received: by mail-pj1-f70.google.com with SMTP id 98e67ed59e1d1-38ea32e57e2so1817295a91.1 for ; Fri, 18 Sep 2026 08:45:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789746354; x=1790351154; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=R++qxNNJJnPJa7wkOafzLmSyQyGcVXcxVtQxZqs7iqM=; b=QK+rpOZXHn6iLNjK6l/itjf2+N4qNveYAKl6TD/uTlapuDiBkRODcihFZQaFEcOIez IzMl6V9keua8y7IM+S2AE7cx8RpS/493tXGr3UAMFOyZS4R0nmuiVqCbrNJm36k+PUPa 2xmobsvk93CMDNOum3Dh9Av+Ml7mLpbZNs+g6750JZXDladxBINK/gBsTgMgj+i3sEck QYKcnJmdvdoyaDsvAASLEV5JVK2Ib7qx6zRtNOV2yrZFFFvpCOoU/D4zrEimADcRlis1 DBvXUERIU8s38pFEjpChbQiTQvSdMQc6q0LisZ6zqg2BNy4A/Rblc4zVlgUhKfv6XafR whnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789746354; x=1790351154; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=R++qxNNJJnPJa7wkOafzLmSyQyGcVXcxVtQxZqs7iqM=; b=VAzNAz2eLOnM8Bk4IvqVuIpqAkg7+jvjwNYt8/tUwvREm0OakM2TD0ka1m4Y2H3xAP bzHSsdMk0Jrfo/trZPrJyvY+0UsQJoEC/JnEF7N3pTPpSEfTfviAEl7xvGctO7gR9PzX ujIjv0dmUVIbZfHrQ1xnwXbQ8qAtU4mCGcVJdGpvWbWEncVP+umhbBNlClmduuY1vZYm DyOyYEaiJip/WwSQipov2nys7f8PkddsbGMulBDtAvEQ3+YiKnesa6ZgYVboyPqy9koI WhtmGg8z2x0/FNILXGTQ1HsvPy1xRjw6uKD997tJg1X79flpE4FeFNYHjr0Ef7TRd3/+ SAaA== X-Forwarded-Encrypted: i=1; AKwUvBwAMqNUwZGZiDn1RsZmmV5gMEQ7nJfL3xndREf6hmJFWB5LiG1KfLjtMTdxZ0c6zsXoKHIzrnF8VrNQC9I=@vger.kernel.org X-Gm-Message-State: AFuF++nAnlW4Te+vfmKgD4G4R8QFqZToZ7zEleX6Z3JjqklJF6/+nuGc TsnJnELjXaQ24NZBQZqF/pEFc1K6Vk9U1mjwuccZoqKcCGyDS7witu2mp01CjYR5cWD/L4rt4tP 7Im5hgEX4ZTw08A== X-Received: from pjbiw4.prod.google.com ([2002:a17:90b:4204:b0:39d:a2e8:6890]) (user=jmattson job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:57e8:b0:39e:4c7f:8b19 with SMTP id 98e67ed59e1d1-39e54d458b7mr6747764a91.30.1789746353963; Fri, 18 Sep 2026 08:45:53 -0700 (PDT) Date: Fri, 18 Sep 2026 08:45:30 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <20260918154530.4129698-1-jmattson@google.com> Subject: [PATCH] KVM: x86: Disallow EFER.LMSLE when EferLmsleUnsupported is set in guest CPUID From: Jim Mattson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Nikunj A Dadhania , Yosry Ahmed , Jim Mattson Content-Type: text/plain; charset="UTF-8" Reject guest writes to EFER (and nested VMRUN with VMCB12 EFER) that set EFER.LMSLE when CPUID.80000008H:EBX.EferLmsleUnsupported[bit 20] is set in the guest's CPUID. Commit c53c632592a4 ("KVM: SVM: Disallow EFER.LMSLE when not supported by hardware") prevented EFER.LMSLE from being enabled in supported_efer_bits on hosts that set EferLmsleUnsupported, but missed checking the guest CPUID capability in __kvm_valid_efer(). As a result, on a host that supports EFER.LMSLE (e.g. Rome), a guest whose userspace VMM sets EferLmsleUnsupported in guest CPUID (e.g. for migration compatibility with Milan, Genoa, or Turin) can still set EFER.LMSLE without triggering a #GP. Fixes: c53c632592a4 ("KVM: SVM: Disallow EFER.LMSLE when not supported by hardware") Assisted-by: LLM Signed-off-by: Jim Mattson --- arch/x86/kvm/msrs.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/msrs.c b/arch/x86/kvm/msrs.c index dd3bb04878ca..6dbaf063cc8d 100644 --- a/arch/x86/kvm/msrs.c +++ b/arch/x86/kvm/msrs.c @@ -598,8 +598,11 @@ static bool __kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer) if (efer & EFER_NX && !guest_cpu_cap_has(vcpu, X86_FEATURE_NX)) return false; - return true; + if (efer & EFER_LMSLE && + guest_cpu_cap_has(vcpu, X86_FEATURE_EFER_LMSLE_MBZ)) + return false; + return true; } bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer) { -- 2.55.0.1082.g2b9226bbc0-goog