From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: VMX: Update instruction length on intercepted BP Date: Sun, 14 Feb 2010 14:27:00 +0200 Message-ID: <4B77EC14.4000302@redhat.com> References: <4B767160.4070609@web.de> <20100214075303.GF2511@redhat.com> <4B77CFD7.9080504@web.de> <20100214103445.GH2511@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Jan Kiszka , Marcelo Tosatti , kvm To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:2408 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754154Ab0BNM1E (ORCPT ); Sun, 14 Feb 2010 07:27:04 -0500 In-Reply-To: <20100214103445.GH2511@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 02/14/2010 12:34 PM, Gleb Natapov wrote: >>> >>> event_exit_inst_len is only used for event reinjection. Since event >>> intercepted here will not be reinjected why updating event_exit_inst_len >>> is needed here? >>> >> In guest debugging mode a #BP exception is always reported to user space >> to find out what caused it. If it was the guest itself, the exception is >> reinjected, on older kernels via KVM_SET_GUEST_DEBUG and since 2.6.33 >> via KVM_SET_VCPU_EVENTS (the latter requires some qemu patch that I will >> post later). >> >> As we currently do not update event_exit_inst_len on #BP exits, >> reinjecting fails unless event_exit_inst_len happens to be 1 from some >> other exit. >> >> > Hmm, how does it work on SVM then where we do not have > event_exit_inst_len so execution will resume on the same rip that caused > #BP after event reinjection? > > Note, newer AMDs do have such a field (nRIP, 0xC8). We need to support older machines, though. -- error compiling committee.c: too many arguments to function