From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (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 7585816C69B for ; Tue, 7 May 2024 14:21:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715091692; cv=none; b=r/xgGYIk5IiEoMCGd2mP9F95xJbbcj1Vv7r6+58INCKczq04JnhmtqZB9D33Tu7RkIrPeTGqRI7tSa3y2hnMPNTfJ9qGftvplEO5epj2i4WL21n2hPnjBQvLToiIo6yVVUOpgAkkWwDooEiOmbJzsdCDkbaA1D5rouMULz2LLWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715091692; c=relaxed/simple; bh=8QYdibYVRNGlJBkqihgTrWLMvE6OLOwqy6jEWIRcti8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=mbC+57uHV70/8w55TtS+wTQL4IflWM8IKZdIdCK5hUvAIpj+NVDHJnX+bFubvySewfKKruSmmLM5JTG+52cK5srGgmKZvZdVEGHuHr6LAgOAeQl9ni89bNE4g8HsNhmvP/PwF/jYwamZlqwM3ksunwMKRZQW+qXcTpDNlBjEYt4= 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=FZOYk/qm; arc=none smtp.client-ip=209.85.219.201 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="FZOYk/qm" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-de54ccab44aso6489443276.3 for ; Tue, 07 May 2024 07:21:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1715091690; x=1715696490; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=WlQ1ODIcC8LnzvsFQdv3tqPlhpmjYXCiPBeyIiWiI7o=; b=FZOYk/qmgGxpQKKrmMyDY5df994gwzVMb+ejlxrGSqcP1HxZ8qofU8HUg9SqiNnL45 029oQAeOXM7oUx8N4zSfZ6Dike+MnZZ3b7zAAdYf0fy7PZZU2i8c810m3LJBkf7f3xwb +xm7DRTKM1H/dhb/qABxLdiawlpIejGtVzwT2wE75O5KKrlH4X+/9SCHFpnGM4eCAjah TaX9VlBgTqnvCVwCNhbth5x9IFdB5hwr4zol0qUCLVpDQi+RE4vCrJ2x0NEpS6Pu0OuY /8sq8ZdORlhuuOglfY3tJk9TL6ff3pXWjhofWep5frsDmqDyHh9ivsq+0lp2+pBvt2ol mCsQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715091690; x=1715696490; h=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; bh=WlQ1ODIcC8LnzvsFQdv3tqPlhpmjYXCiPBeyIiWiI7o=; b=hwP8SVdd1mAgKSbgTn3tKiwjHfXpjwlcctHBnuTUW5eA48qPft9TnnBWW2QHsm8qkP dClTKPgQHQCGFrokLN9kl6HNJ2bDS5+vdzJtU/FwCrqBCcHRtq8f5bRZyHM03fN//y4Q nNtYgX+HWa/lK/q0j15LzWIXu0aUgD2CNO/RBXZdVnPjRvlBvo59R8FKaIQJ6dADhr0F eO8qjC1Lbuj+ft7N2KtByqFsuA9ig6pp/OtFO05rKUqhdldAUH59ZqUwc8kYYrV9sUR8 2YeOsPRHZPkoFB2Vkm3N8cPLOPCp4/6ge59Jir12bbX/Mm020GnrlNBSErw7xnByfYxB J1Iw== X-Forwarded-Encrypted: i=1; AJvYcCXan3msWiiL4Hf16f6aSh1zUepZkF+EtS91SNT6J705gBUvh5roZmmcYmmTpSsr5msbCkYFmSjIQRzH9Hg2KsucnmEY X-Gm-Message-State: AOJu0YwJNt57sFioVHGSGaWX7hy/Fbn2b172ptQFDehVfgGxxgSylGck oodJ9Sa0vbk3M6o7H+G0j/+lPFXAfBwskFjSvf8DWQyu4E94yUsYY14hy8qNgcRsHmkskqlCT9v lVg== X-Google-Smtp-Source: AGHT+IGQflJmsb6ITkvKxK5+27cDVP96WKoxLdJLDdOq9myYIbuYllja2Yh8BEpJiRr7bbUZVOQJEVjPros= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1004:b0:de4:7be7:1c2d with SMTP id w4-20020a056902100400b00de47be71c2dmr4460818ybt.11.1715091690487; Tue, 07 May 2024 07:21:30 -0700 (PDT) Date: Tue, 7 May 2024 07:21:28 -0700 In-Reply-To: <8a6c88c7457f9677449b0be3835c7844b34b4e8a.camel@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240219074733.122080-1-weijiang.yang@intel.com> <20240219074733.122080-25-weijiang.yang@intel.com> <038379acaf26dd942a744290bde0fc772084dbe9.camel@intel.com> <8a6c88c7457f9677449b0be3835c7844b34b4e8a.camel@intel.com> Message-ID: Subject: Re: [PATCH v10 24/27] KVM: x86: Enable CET virtualization for VMX and advertise to userspace From: Sean Christopherson To: Rick P Edgecombe Cc: Chao Gao , Dave Hansen , "x86@kernel.org" , "pbonzini@redhat.com" , "peterz@infradead.org" , "john.allen@amd.com" , "linux-kernel@vger.kernel.org" , Weijiang Yang , "mlevitsk@redhat.com" , "kvm@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" On Mon, May 06, 2024, Rick P Edgecombe wrote: > I don't immediately see what trouble will be in giving kernel IBT a disable > parameter that doesn't touch X86_FEATURE_IBT at some point in the future. Keeping X86_FEATURE_IBT set will result in "ibt" being reported in /proc/cpuinfo, i.e. will mislead userspace into thinking IBT is supported and fully enabled by the kernel. For a security feature, that's a pretty big issue. To fudge around that, we could add a synthetic feature flag to let the kernel tell KVM whether or not it's safe to virtualize IBT, but I don't see what value that adds over KVM checking raw host CPUID.