From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v2] KVM: VMX: Update instruction length on intercepted BP Date: Wed, 17 Feb 2010 12:23:39 +0100 Message-ID: <4B7BD1BB.7090909@siemens.com> References: <4B795FD0.4060505@siemens.com> <20100216073352.GV2995@redhat.com> <4B7A51D4.1040701@web.de> <20100216082455.GY2995@redhat.com> <4B7A612A.4010603@siemens.com> <20100217104304.GP2995@redhat.com> <4B7BCF59.40402@redhat.com> <20100217111641.GS2995@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Marcelo Tosatti , kvm To: Gleb Natapov Return-path: Received: from goliath.siemens.de ([192.35.17.28]:23104 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752340Ab0BQLX7 (ORCPT ); Wed, 17 Feb 2010 06:23:59 -0500 In-Reply-To: <20100217111641.GS2995@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Gleb Natapov wrote: > On Wed, Feb 17, 2010 at 01:13:29PM +0200, Avi Kivity wrote: >> On 02/17/2010 12:43 PM, Gleb Natapov wrote: >>>> And, again: This is an _existing_ user space ABI. We could only provide >>>> an alternative, but we have to maintain what is there at least for some >>>> longer grace period. >>>> >>> But it was always broken for SVM and was broken for VMX for a year and >>> nobody noticed, so may be instead of reintroducing old interface we should >>> do it right this time? >> We need to fix the existing interface first, and then think long and >> hard if we want yet another interface, since we're likely to screw >> it up as well. >> >> The more interfaces we introduce, the harder maintenance becomes. >> > We are in a sad state if we cannot improve interface. The current one > outsource part of CPU functionality into userspace. This should be a big > no-no. I still disagree on this. Moving the decision logic to user space prevented to re-implement a gdbstub in kernel space. I oversaw that re-injecting #BP over older SVM was broken, but it is now fixed for all vendors. So moving it back to kernel has actually no long-term reason. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux