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[23.128.96.18]) by mx.google.com with ESMTP id c17si272352ejm.84.2020.04.27.11.49.05; Mon, 27 Apr 2020 11:49:30 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726624AbgD0SrI (ORCPT + 99 others); Mon, 27 Apr 2020 14:47:08 -0400 Received: from mga05.intel.com ([192.55.52.43]:20616 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726249AbgD0SrI (ORCPT ); Mon, 27 Apr 2020 14:47:08 -0400 IronPort-SDR: PRC6689qJ1oUsyFvOsRNFva+d0TxYT0Nt9C2cLQtC0CJJnAOZsJySNeZS4DLFTG4Uvp54TPDpN bpoHnqDFaIvw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Apr 2020 11:47:08 -0700 IronPort-SDR: tMRtVWJYS1g//srvZYmJ2nFAv6Wb5tQeTTBE/WbF5xB2QrFFDh6VQW2DqK0OwiIGflsdk5wXw3 3SAMWLsKrYlA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,325,1583222400"; d="scan'208";a="260825823" Received: from jbarra4x-mobl2.amr.corp.intel.com (HELO [10.252.135.2]) ([10.252.135.2]) by orsmga006.jf.intel.com with ESMTP; 27 Apr 2020 11:47:07 -0700 Subject: Re: [PATCH] Allow RDTSC and RDTSCP from userspace To: Joerg Roedel Cc: Tom Lendacky , Mike Stunes , joro@8bytes.org, dan.j.williams@intel.com, dave.hansen@linux.intel.com, hpa@zytor.com, jgross@suse.com, jslaby@suse.cz, keescook@chromium.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, luto@kernel.org, peterz@infradead.org, thellstrom@vmware.com, virtualization@lists.linux-foundation.org, x86@kernel.org, Sean Christopherson References: <20200319091407.1481-56-joro@8bytes.org> <20200424210316.848878-1-mstunes@vmware.com> <2c49061d-eb84-032e-8dcb-dd36a891ce90@intel.com> <4d2ac222-a896-a60e-9b3c-b35aa7e81a97@intel.com> <20200425124909.GO30814@suse.de> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20200425124909.GO30814@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/25/20 5:49 AM, Joerg Roedel wrote: >> That's a fun point because it means that the (untrusted) hypervisor can >> cause endless faults. I *guess* we have mitigation for this with our >> stack guard pages, but it's still a bit nasty that the hypervisor can >> arbitrarily land a guest in the double-fault handler. >> >> It just all seems a bit weak for the hypervisor to be considered >> untrusted. But, it's _certainly_ a steep in the right direction from SEV. > Yeah, a malicious hypervisor can do bad things to an SEV-ES VM, but it > can't easily steal its secrets from memory or registers. The #VC handler > does its best to just crash the VM if unexpected hypervisor behavior is > detected. This is the kind of design information that would be very useful to reviewers. Will some of this information make it into the cover letter eventually? Or, Documentation/? Also, for the security purists, an SEV-ES host is still trusted (in the same TCB as the guest). Truly guest-untrusted VMMs won't be available until SEV-SNP, right?