From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valentine Sinitsyn Subject: Re: Nested paging in nested SVM setup Date: Thu, 19 Jun 2014 11:03:59 +0600 Message-ID: <53A26F3F.6020504@gmail.com> References: <53A179C4.9060203@gmail.com> <53A18A6D.2050407@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: Jan Kiszka , kvm@vger.kernel.org Return-path: Received: from mail-la0-f48.google.com ([209.85.215.48]:60146 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757231AbaFSFEF (ORCPT ); Thu, 19 Jun 2014 01:04:05 -0400 Received: by mail-la0-f48.google.com with SMTP id el20so1067467lab.21 for ; Wed, 18 Jun 2014 22:04:03 -0700 (PDT) In-Reply-To: <53A18A6D.2050407@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: Hi all, > If we want to provide useful nested SVM support, this must be feasible. > If there is a bug, it has to be fixed. I did a quick look on KVM sources this morning, and although I can be wrong, this really looks like a bug. The reason is nested_svm_vmrun() doesn't do anything to host or guest PATs (thus no easy way to set memory type if NPT is used and guest PAT has non-default value). And since svm_set_cr0() explicitly clears CD (for a good reason, I suppose), there seem to be no way to control caching from the nested setup altogether. -- Regards, Valentine Sinitsyn