From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5998C433ED for ; Fri, 2 Apr 2021 15:27:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89ADC6113E for ; Fri, 2 Apr 2021 15:27:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235986AbhDBP1m (ORCPT ); Fri, 2 Apr 2021 11:27:42 -0400 Received: from mga09.intel.com ([134.134.136.24]:21577 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236421AbhDBP1g (ORCPT ); Fri, 2 Apr 2021 11:27:36 -0400 IronPort-SDR: mY0QcfNJJUBsTYxnuDE8e0fD50cIQcUH+XX9nviRpqB6G1a+68bsuuDap+POMD3fHu8njXnEjk rXaHkgQ4za5A== X-IronPort-AV: E=McAfee;i="6000,8403,9942"; a="192589183" X-IronPort-AV: E=Sophos;i="5.81,300,1610438400"; d="scan'208";a="192589183" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Apr 2021 08:27:18 -0700 IronPort-SDR: k+Nv7Te4Mnz2pyI3wiaM6EnmatjwAdgiZYSNXGvEdWULkMTnLjmIKCnNZnbskPFP9cirW94dsY vPTBIQL1Hf6Q== X-IronPort-AV: E=Sophos;i="5.81,300,1610438400"; d="scan'208";a="456464618" Received: from danagy-mobl.amr.corp.intel.com (HELO [10.209.45.147]) ([10.209.45.147]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Apr 2021 08:27:18 -0700 Subject: Re: [RFC v1 00/26] Add TDX Guest Support To: Andi Kleen Cc: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org References: <95e97456-478b-c6a2-f851-3b19ce794262@intel.com> <20210402024852.GK1285835@tassilo.jf.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210402024852.GK1285835@tassilo.jf.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/1/21 7:48 PM, Andi Kleen wrote: >> I've heard things like "we need to harden the drivers" or "we need to do >> audits" and that drivers might be "whitelisted". > > The basic driver allow listing patches are already in the repository, > but not currently posted or complete: > > https://github.com/intel/tdx/commits/guest That lists exactly 8 ids: > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1000 }, /* Virtio NET */ > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1001 }, /* Virtio block */ > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1003 }, /* Virtio console */ > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1009 }, /* Virtio FS */ > > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1041 }, /* Virtio 1.0 NET */ > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1042 }, /* Virtio 1.0 block */ > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1043 }, /* Virtio 1.0 console */ > { PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1049 }, /* Virtio 1.0 FS */ How many places do those 8 drivers touch MMIO? >> Are there any "real" hardware drivers >> involved like how QEMU emulates an e1000 or rtl8139 device? > > Not currently (but some later hypervisor might rely on one of those) > >> What about >> the APIC or HPET? > > No IO-APIC, but the local APIC. No HPET. Sean seemed worried about other x86-specific oddities. Are there any more, or is the local APIC the only non-driver MMIO? >> Without something concrete, it's really hard to figure out if we should >> go full-blown paravirtualized MMIO, or do something like the #VE >> trapping that's in this series currently. > > As Sean says the concern about MMIO is less drivers (which should > be generally ok if they work on other architectures which require MMIO > magic), but other odd code that only ran on x86 before. > > I really don't understand your crusade against #VE. It really > isn't that bad if we can avoid the few corner cases. The problem isn't with #VE per se. It's with posting a series that masquerades as a full solution while *NOT* covering or even enumerating the corner cases. That's exactly what happened with #VE to start with: it was implemented in a way that exposed the kernel to #VE during the syscall gap (and the SWAPGS gap for that matter). So, I'm pushing for a design that won't have corner cases. If MMIO itself is disallowed, then we can scream about *any* detected MMIO. Then, there's no worry about #VE nesting. No #VE, no #VE nesting. We don't even have to consider if #VE needs NMI-like semantics. > For me it would seem wrong to force all MMIO for all drivers to some > complicated paravirt construct, blowing up code side everywhere > and adding complicated self modifying code, when it's only needed for very > few drivers. But we also don't want to patch every MMIO to be special cased > even those few drivers. > > #VE based MMIO avoids all that cleanly while being nicely non intrusive. But, we're not selling used cars here. Using #VE is has downsides. Let's not pretend that it doesn't. If we go this route, what are the rules and restrictions? Do we have to say "no MMIO in #VE"? I'm really the most worried about the console. Consoles and NMIs have been a nightmare, IIRC. Doesn't this just make it *WORSE* because now the deepest reaches of the console driver are guaranteed to #VE? Which brings up another related point: How do you debug TD guests? Does earlyprintk work?