From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58184) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dIb7f-0001UU-9J for qemu-devel@nongnu.org; Wed, 07 Jun 2017 09:35:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dIb7a-0004M5-CE for qemu-devel@nongnu.org; Wed, 07 Jun 2017 09:35:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35754) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dIb7a-0004Lm-6I for qemu-devel@nongnu.org; Wed, 07 Jun 2017 09:35:38 -0400 References: <20170606171320.GA8115@flamenco> <877f0o3vbn.fsf@frigg.lan> From: Paolo Bonzini Message-ID: <000023f1-57a6-b211-d9d1-87b8f39326d5@redhat.com> Date: Wed, 7 Jun 2017 15:35:33 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] GSoC 2017 Proposal: TCG performance enhancements List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell , "Emilio G. Cota" , Pranith Kumar , =?UTF-8?Q?Alex_Benn=c3=a9e?= , qemu-devel , Richard Henderson , Alessandro Di Federico On 07/06/2017 14:07, Peter Maydell wrote: >> My understanding was that adding a public instrumentation interface would add >> too much code maintenance overhead for a feature that is not in QEMU's core >> target. > Well, it depends what you define as our core target :-) > I think we get quite a lot of users that want some useful ability > to see what their guest code is doing, and these days (when > dev board hardware is often very cheap and easily available) and virtualization is too... > I think that's a lot of the value that emulation can bring to > the table. Obviously we would want to try to do it in a way > that is low-runtime-overhead and is easy to get right for > people adding/maintaining cpu target frontend code... Indeed. I even sometimes use TCG -d in_asm,exec,int for KVM unit tests, because it's easier to debug them that way :) so introspection ability is welcome. Related to this is also Alessandro's work to librarify TCG (he has a TCG->LLVM backend for example).