From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751721AbbIORcz (ORCPT ); Tue, 15 Sep 2015 13:32:55 -0400 Received: from goliath.siemens.de ([192.35.17.28]:46062 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751070AbbIORcy (ORCPT ); Tue, 15 Sep 2015 13:32:54 -0400 Subject: Re: [PATCH] KVM: nVMX: nested VPID emulation To: Wanpeng Li , Paolo Bonzini References: <55F6DF9D.5070508@siemens.com> Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org From: Jan Kiszka Message-ID: <55F8563D.3050905@siemens.com> Date: Tue, 15 Sep 2015 19:32:45 +0200 User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2015-09-15 12:14, Wanpeng Li wrote: > On 9/14/15 10:54 PM, Jan Kiszka wrote: >> Last but not least: the guest can now easily exhaust the host's pool of >> vpid by simply spawning plenty of VCPUs for L2, no? Is this acceptable >> or should there be some limit? > > I reuse the value of vpid02 while vpid12 changed w/ one invvpid in v2, > and the scenario which you pointed out can be avoid. I cannot yet follow why there is no chance for L1 to consume all vpids that the host manages in that single, global bitmap by simply spawning a lot of nested VCPUs for some L2. What is enforcing L1 to call nested vmclear - apparently the only way, besides destructing nested VCPUs, to release such vpids again? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux