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 4FEF6C7EE2F for ; Tue, 30 May 2023 18:53:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233001AbjE3SxU (ORCPT ); Tue, 30 May 2023 14:53:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232541AbjE3SxL (ORCPT ); Tue, 30 May 2023 14:53:11 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62B30106; Tue, 30 May 2023 11:53:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=6s4clEUBhhObMRbaHbpA0SDItwb8X/szVpDv0tngd0A=; b=AeSDmHAYyUo4rOKMXZZk+/nFPL FJw7VkJZdv6K3ADKyqTZXfhZ1ix3cKN+04ysDnLWBUwDTOLPY8earrajsV5xyrfwinAq5KjnK0Ele qaDnhSk4MhoUsenWd6lACG+tCHHMONTgTw5NB5NaGiAaAIdryJWxXgVGq/XxT2C/BxAO7mtPhSQ+w bC8cl53NYPCTpYas0neg5kccPXTQ9a7b0DZ8BNProB4z//TPKmZgTwmqqJ/kLKMTmd4ufTTlhpV5f Jw1vY0vEdulVKgF4FYt4bHs0tpVdNgPfX/MIopAXv1kePNq+/gw+28aAPsjXMnQIoRAbKCmitw4C4 2drd0a8A==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1q44SR-006XRv-6t; Tue, 30 May 2023 18:52:35 +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 D6079300194; Tue, 30 May 2023 20:52:32 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BDB2124147355; Tue, 30 May 2023 20:52:32 +0200 (CEST) Date: Tue, 30 May 2023 20:52:32 +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: <20230530185232.GA211927@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0f0ab135-cdd0-0691-e0c1-42645671fe15@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 30, 2023 at 10:59:01AM -0500, Tom Lendacky wrote: > On 5/30/23 09:35, Peter Zijlstra wrote: > > On Tue, May 30, 2023 at 02:16:55PM +0200, Gupta, Pankaj wrote: > > > > > > > > Add a #HV exception handler that uses IST stack. > > > > > > > > > > > > > Urgh.. that is entirely insufficient. Like it doesn't even begin to > > > > start to cover things. > > > > > > > > The whole existing VC IST stack abuse is already a nightmare and you're > > > > duplicating that.. without any explanation for why this would be needed > > > > and how it is correct. > > > > > > > > Please try again. > > > > > > #HV handler handles both #NMI & #MCE in the guest and nested #HV is never > > > raised by the hypervisor. > > > > I thought all this confidental computing nonsense was about not trusting > > the hypervisor, so how come we're now relying on the hypervisor being > > sane? > > 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.