From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [80.241.56.151]) (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 219741C5F12; Wed, 11 Dec 2024 08:54:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.151 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733907262; cv=none; b=GKEn6Q3dk4X8yEpdMqVqWbKSU11Vhj4/HAlFOK7WSW5MZImWKwf2uwRJvxxXyHHCGXsJep1lQc85l2xh4Oha/8T1l9KbQWVNsfSee0HuK26RoMvpiMbj/HFUwX3fnnWdvRsMLJX58f10e61qXTm581nWRxgTO3ch3PdQ5xPFsdk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733907262; c=relaxed/simple; bh=gt/brD+bFKcK0ciXmNboabynGmPsZN1ysJlSHAaLOWs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=le5sjdv0s5tdFmEiHFtxliGmmJQ+8KSgplJQj7Ft1xA4d99Y1NHUDjIGmeOvztGB95a2NpZDxRzrndwL6do44GzP+IsOayvvh6ScVLAfU6WnggcM3haW7N8VygT2ikvd+3mOewFQx1G/2R1h6TQpVCaAcwo2wbus+tpq5pG2E/M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org; spf=pass smtp.mailfrom=mailbox.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=jgRS2uZJ; arc=none smtp.client-ip=80.241.56.151 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mailbox.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="jgRS2uZJ" Received: from smtp2.mailbox.org (smtp2.mailbox.org [IPv6:2001:67c:2050:b231:465::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-101.mailbox.org (Postfix) with ESMTPS id 4Y7TtJ3jS2z9snp; Wed, 11 Dec 2024 09:54:16 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1733907256; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hgxGiDC40w1nBBtzUl+GNZ+rfEtSNj7LHPhUGuQr2aw=; b=jgRS2uZJNbPEVpIg0Vr8fWPf3xxgJzwuh4TArvMRlD9w4XwhDGYFI0KEyebhNhgGXe4GvS iwyXoiNqIxiTTd+my5L91J9W5hXPwfF2o/+9sXsMlNjlRqiph8c3vL4ZsMynrDI7EJtSn5 8Zaj2Op4NrSS/426FhGFX91TSCSwX+JxNQ/+//7B+UpKmFonktE/Oil31RBk5UCkOrGPuv xm7KuTWswkAM8XaIaaoOmO6fYuufgO5dEpKI+UWu+68iVwOs+3DqAOtF3iSDCSGn6cuxjj vmvAMzEV/OSU1FN8zeOJu8kAM7bYRhqDuzMFB2bsW6C028mEFBGlqg1Z87EYEg== Message-ID: <376c445a-9437-4bdd-9b67-e7ce786ae2c4@mailbox.org> Date: Wed, 11 Dec 2024 09:54:14 +0100 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [REGRESSION] from 74a0e79df68a8042fb84fd7207e57b70722cf825: VFIO PCI passthrough no longer works To: Sean Christopherson Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, regressions@lists.linux.dev, Tom Lendacky References: <52914da7-a97b-45ad-86a0-affdf8266c61@mailbox.org> <93a3edef-dde6-4ef6-ae40-39990040a497@mailbox.org> <9e827d41-a054-5c04-6ecb-b23f2a4b5913@amd.com> Content-Language: en-GB From: Simon Pilkington In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-MBO-RS-META: 89z9y4wrg7c6jtbyixkhzihp6uj115ee X-MBO-RS-ID: c5aa5748a771390c19e On 10/12/2024 23:43, Sean Christopherson wrote: > Unless you (Tom) disagree, I vote to simply drop the offending code, i.e. make > all supported bits fully writable from the guest. KVM is firmly in the wrong here, > and I can't think of any reason to disallow the guest from clearing LFENCE_SERIALIZE. > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 6a350cee2f6c..5a82ead3bf0f 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -3201,15 +3201,6 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) > if (data & ~supported_de_cfg) > return 1; > > - /* > - * Don't let the guest change the host-programmed value. The > - * MSR is very model specific, i.e. contains multiple bits that > - * are completely unknown to KVM, and the one bit known to KVM > - * is simply a reflection of hardware capabilities. > - */ > - if (!msr->host_initiated && data != svm->msr_decfg) > - return 1; > - > svm->msr_decfg = data; > break; > } > This also produces a good kernel.