From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) (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 94C0427603A for ; Thu, 27 Aug 2026 13:48:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787838499; cv=none; b=Xhd1dWvNkKl1s8nvwBYg1g2B9TAAK4Qm2B8AybezmNufBA/jV9lsbr5O8qnyoRDzLQUPEUCZsaAxDOdNZFrVv0JwUSb/kzy/eVGLnghzypNe9qoRPnI2Jyg0KPFx6ancfl4xoJYWPId/nZx7Ft04NDk2pjf2HQ8x4PNuGqupp8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787838499; c=relaxed/simple; bh=xXafbhcFPPSSpbzTZbsGVk1pCy0s7pK8aW5HRziv4MM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=amOh5CzzeLeL1vqvegzrrjoCD0593Cc90agx/asNLg8netixC6hgVIOHPeUkUjKgPLOtTLbiYglQbdo9TJztKHqfvcLkz3OMVwvsfxBdO2lEDJHb8mX5BoaEN1+Uq8LEcPTfQi4m/78W3xz1UGbeH1+TlBaHtXbtktcSAeGybuk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=WJQDrDCb; arc=none smtp.client-ip=209.85.215.200 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="WJQDrDCb" Received: by mail-pg1-f200.google.com with SMTP id 41be03b00d2f7-cc15155cde2so2687661a12.2 for ; Thu, 27 Aug 2026 06:48:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787838498; x=1788443298; darn=vger.kernel.org; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date:from:to:cc :subject:date:message-id:reply-to:content-type; bh=DusLiqhfhbPeCoA/ZnAQoMsY29GgMuSSwGngcrjqGF4=; b=WJQDrDCbit8alwevbA4+eAu+sGC7xLaLchNqZTaxlvllxabNYHo6PnMgW0kOLArHnG spoeVjdqWU07aIK0s6vIjETshWvJi2Hk/0h3YXcDR4/0fY+UB6KWDyxbTROD53OqtX3k mTdyIjQG3EpYifDfh0G2ALDO+jo31NR/4CFDc2LXHBcuOP0ImdCnfRNYStfPStLCa5mO 50kV+atEEGbkDcsEyQS2i4A2mdICP03mxF2oztv6YVQa+DszNIdJ1L5l1U/K7QfyB8+Q RfFrvaQem5En+lio3lLZSp1uKw8un/piGdN883Gd/9NrB2iKnSGwn5LXT47MgeC5R+6d 1aNg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787838498; x=1788443298; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=DusLiqhfhbPeCoA/ZnAQoMsY29GgMuSSwGngcrjqGF4=; b=G/W+oQptXuqlFjId/vky4sUyILr0Ovgw1Nn9SX0DzvHOWkqgMLhHdZjKCd81v/iB1k ngruAMyoWzRLvGdrgjqSWKKZ11VfTcgRC/hD6TChzZMhtQcPYuTTlXsS//u/3XqC6Ub4 0XNn6lPwgTsN6Wd3GPzFglFqbQ5lLloDEGUNW+WXn8dsIJAWKmifhAC7p+f2wyZeYbpR FbKoeBvX7S+Gqeq/7nn0ZCPSeHtGmwS2ymL3gPAlPiviOPTRoAuHgTmids7E824IlTFG 9Z6h488RvGUANYTC/zbEhyVIsKxoZhMchDoOL8yQwl4qamIEedBM8CLI5dVQNBCjbMZ5 XLsA== X-Forwarded-Encrypted: i=1; AHgh+RoRQ67yyUuIfoCUQbvadzt1ggLxcJPKTrt6lJlLnep6XaXg3SPk990fLDNeLV+0q7otTnU=@vger.kernel.org X-Gm-Message-State: AFuF++nZWizOyGawK+6csI1CBj80pXwv5Ouh8TE4O/Wl3FdhnTIIv3gl a6bMEb0FC/stWJYB/tBnPGv2r5Cv7SLdaYzM/weHqnDze9UkxnU5Rw/SqrJX8spTMffeqUCYZ8B cWAyaVA== X-Received: from pgcp5.prod.google.com ([2002:a63:7405:0:b0:cc1:c65d:a776]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:3117:b0:3bf:a543:e7f5 with SMTP id adf61e73a8af0-3cf7586efb2mr34803020637.3.1787838497602; Thu, 27 Aug 2026 06:48:17 -0700 (PDT) Date: Thu, 27 Aug 2026 06:48:17 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260826211844.884951-1-seanjc@google.com> <20260826211844.884951-3-seanjc@google.com> Message-ID: Subject: Re: [PATCH 2/4] KVM: x86/mmu: Bug the VM if KVM attempts to walk more levels than the MMU has From: Sean Christopherson To: Yosry Ahmed Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Teodorescu Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Thu, Aug 27, 2026, Yosry Ahmed wrote: > On Wed, Aug 26, 2026 at 2:18=E2=80=AFPM Sean Christopherson wrote: > > > > Extend the "EFER.LMA && !CR4.PAE" check, which exists largely to guard > > against KVM configuring a paging32 MMU with more than 2 levels of pagin= g, >=20 > Is there value in keeping the original check? I suppose yes as you > said it exists "largely" for this, but it would probably be nice to > spell it out (if we know). Because LMA && !PAE is still an illegal combination. The symptom we know a= bout is a misconfiguration of base.level vs. the paging template, but I also wan= t to guard against any other symptoms that stem from the bad state.