From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH] KVM: nVMX: nested VPID emulation Date: Tue, 15 Sep 2015 19:32:45 +0200 Message-ID: <55F8563D.3050905@siemens.com> References: <55F6DF9D.5070508@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Wanpeng Li , Paolo Bonzini Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.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