From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH v2 28/30] KVM: x86 emulator: restart string instruction without going back to a guest. Date: Mon, 15 Mar 2010 11:44:47 +0200 Message-ID: <20100315094447.GG4294@redhat.com> References: <1268583675-3101-1-git-send-email-gleb@redhat.com> <1268583675-3101-29-git-send-email-gleb@redhat.com> <4B9D1545.2020902@redhat.com> <20100314180625.GB5406@redhat.com> <4B9DE55A.5070003@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: mtosatti@redhat.com, kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:16704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934484Ab0COJot (ORCPT ); Mon, 15 Mar 2010 05:44:49 -0400 Received: from int-mx04.intmail.prod.int.phx2.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.17]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o2F9inVU019562 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 15 Mar 2010 05:44:49 -0400 Content-Disposition: inline In-Reply-To: <4B9DE55A.5070003@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Mar 15, 2010 at 09:44:26AM +0200, Avi Kivity wrote: > On 03/14/2010 08:06 PM, Gleb Natapov wrote: > >>Suggest simply reentering every N executions. > >> > >This restart mechanism is, in fact, needed for ins read ahead to work. > >After reading ahead from IO port we need to avoid entering decoder > >until entire cache is consumed otherwise decoder will clear cache and > >data will be lost. So we can't just enter guest in arbitrary times, only > >when read ahead cache is empty. Since read ahead is never done across > >page boundary this is save place to re-enter guest. > > Please make the two depend on each other directly then. We can't > expect the reader of the emulator code know that. > We can document that. I wouldn't want to have different conditions for guest re-entry for different opcodes. > Have the emulator ask the buffer when it is empty. > It will be always empty for all string ops except INS. -- Gleb.