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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DC97C77B7A for ; Wed, 31 May 2023 09:15:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234875AbjEaJPg (ORCPT ); Wed, 31 May 2023 05:15:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230225AbjEaJPe (ORCPT ); Wed, 31 May 2023 05:15:34 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78BACBE; Wed, 31 May 2023 02:15:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=BDwruifJ4hZC6T+A+Yrq8BWIQU5ks8snAY3EXrTzopM=; b=gtXk9RVrVY8qW8NYf4qE95uoRE lDL4pw+2UmyWib16eFgzZulP/qCV0AZch/9qlddGy0xxTYS7xePFDNkHtpq2uXzVHB4cI5IePtO6/ 8Zc3Ay1ScYT+SzNBEZqLLhilisxAHcOjhWOojuvI8IIJ5yxzKLoZNdSNR+X4TsGmlZFao9/mxkKAC jWxxS89ihv3L6Nld0jQfdqnsCEyxP79jFYGcBaSOktFjvMEkaqBSX+yJovBn1WzSUWN8x0CzXIOoD fz3UOcKB+yZtZ0YcxTYozEfCFDZpWmRqSnN1m/aHAwlLx4XDn6QdfksdOXxY9VjonJWsSMrdpDppU L697pnTg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1q4Huw-00FPuU-1m; Wed, 31 May 2023 09:14:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (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) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BFA94300338; Wed, 31 May 2023 11:14:52 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 99972241EF418; Wed, 31 May 2023 11:14:52 +0200 (CEST) Date: Wed, 31 May 2023 11:14:52 +0200 From: Peter Zijlstra To: Tom Lendacky Cc: "Gupta, Pankaj" , Tianyu Lan , luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, jgross@suse.com, tiala@microsoft.com, kirill@shutemov.name, jiangshan.ljs@antgroup.com, ashish.kalra@amd.com, srutherford@google.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, pawan.kumar.gupta@linux.intel.com, adrian.hunter@intel.com, daniel.sneddon@linux.intel.com, alexander.shishkin@linux.intel.com, sandipan.das@amd.com, ray.huang@amd.com, brijesh.singh@amd.com, michael.roth@amd.com, venu.busireddy@oracle.com, sterritt@google.com, tony.luck@intel.com, samitolvanen@google.com, fenghua.yu@intel.com, pangupta@amd.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [RFC PATCH V6 01/14] x86/sev: Add a #HV exception handler Message-ID: <20230531091452.GG38236@hirez.programming.kicks-ass.net> References: <20230515165917.1306922-1-ltykernel@gmail.com> <20230515165917.1306922-2-ltykernel@gmail.com> <20230516093010.GC2587705@hirez.programming.kicks-ass.net> <20230530143504.GA200197@hirez.programming.kicks-ass.net> <0f0ab135-cdd0-0691-e0c1-42645671fe15@amd.com> <20230530185232.GA211927@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230530185232.GA211927@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 30, 2023 at 08:52:32PM +0200, Peter Zijlstra wrote: > > That should really say that a nested #HV should never be raised by the > > hypervisor, but if it is, then the guest should detect that and > > self-terminate knowing that the hypervisor is possibly being malicious. > > I've yet to see code that can do that reliably. Tom; could you please investigate if this can be enforced in ucode? Ideally #HV would have an internal latch such that a recursive #HV will terminate the guest (much like double #MC and tripple-fault). But unlike the #MC trainwreck, can we please not leave a glaring hole in this latch and use a spare bit in the IRET frame please? So have #HV delivery: - check internal latch; if set, terminate machine - set latch - write IRET frame with magic bit set have IRET: - check magic bit and reset #HV latch