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=-8.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 0229DC71155 for ; Tue, 1 Dec 2020 18:59:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7FE5D20643 for ; Tue, 1 Dec 2020 18:59:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WPgloV7d" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731275AbgLAS7A (ORCPT ); Tue, 1 Dec 2020 13:59:00 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:38786 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730132AbgLAS66 (ORCPT ); Tue, 1 Dec 2020 13:58:58 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606849051; 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: in-reply-to:in-reply-to:references:references; bh=pAuzzb7BbpYaUN9NyFBwlGuXTmyHgvRWMaZqHnBmRH4=; b=WPgloV7dX5nFKF9E2oaBWtyLQvqI1VV3q09nvg+JO3HrHivUt1X5WzGaHwppgsxxE5Blrd TlGP+iEKW0vn+Q/aGWxpq4+eUJcji/s2Ly0QsO5Uqs17u1Y8dUTB6vvEpLdwDeu645RWSX q/ASJMBkx+tOQQfam2Uy11zzGuEQCSs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-60-VQlruColOxuQAe-pFoReoQ-1; Tue, 01 Dec 2020 13:57:28 -0500 X-MC-Unique: VQlruColOxuQAe-pFoReoQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 138F98581A4; Tue, 1 Dec 2020 18:57:26 +0000 (UTC) Received: from work-vm (ovpn-115-1.ams2.redhat.com [10.36.115.1]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9826710021AA; Tue, 1 Dec 2020 18:57:20 +0000 (UTC) Date: Tue, 1 Dec 2020 18:57:17 +0000 From: "Dr. David Alan Gilbert" To: Peter Maydell Cc: Ashish Kalra , Paolo Bonzini , Thomas Lendacky , Brijesh Singh , Eduardo Habkost , kvm-devel , "Michael S. Tsirkin" , Marcelo Tosatti , ssg.sos.patches@amd.com, Markus Armbruster , QEMU Developers , Richard Henderson Subject: Re: [PATCH 01/11] memattrs: add debug attribute Message-ID: <20201201185717.GN4338@work-vm> References: <2ba88b512ec667eff66b2ece2177330a28e657c0.1605316268.git.ashish.kalra@amd.com> <20201201115047.GA15055@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org * Peter Maydell (peter.maydell@linaro.org) wrote: > On Tue, 1 Dec 2020 at 11:51, Dr. David Alan Gilbert wrote: > > > > * Peter Maydell (peter.maydell@linaro.org) wrote: > > > On Mon, 16 Nov 2020 at 19:28, Ashish Kalra wrote: > > > > > > > > From: Brijesh Singh > > > > > > > > From: Brijesh Singh > > > > > > > > Extend the MemTxAttrs to include a 'debug' flag. The flag can be used as > > > > general indicator that operation was triggered by the debugger. > > > > > > > > A subsequent patch will set the debug=1 when issuing a memory access > > > > from the gdbstub or HMP commands. This is a prerequisite to support > > > > debugging an encrypted guest. When a request with debug=1 is seen, the > > > > encryption APIs will be used to access the guest memory. > > > > > > So, what counts as "debug" here, and why are debug requests > > > special? If "debug=1" means "can actually get at the guest memory", > > > why wouldn't every device model want to use it? > > > > SEV has a flag that the guest-owner can set on a VM to enable debug; > > it's rare for it to be enabled; so it's not suitable for use by normal > > devices. It's only there for debug if the guest owner allows you to. > > So if I do a memory transaction with debug=1 then I should expect > that it might come back with a failure status (meaning "this VM > doesn't permit debug") and I should handle that error ? I think that's probably true. Dave > thanks > -- PMM > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK