From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH v1 0/2] KVM: VMX: require EPTP WB (write-back) support Date: Thu, 10 Aug 2017 16:25:49 +0200 Message-ID: <8cdac71b-8d69-e789-082d-fd32b3591755@redhat.com> References: <20170810133512.13442-1-david@redhat.com> <20170810142309.GA22461@flask> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: kvm@vger.kernel.org, Paolo Bonzini , Bandan Das To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48617 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751492AbdHJOZx (ORCPT ); Thu, 10 Aug 2017 10:25:53 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 45FEE6E5CE for ; Thu, 10 Aug 2017 14:25:53 +0000 (UTC) In-Reply-To: <20170810142309.GA22461@flask> Content-Language: en-US Sender: kvm-owner@vger.kernel.org List-ID: On 10.08.2017 16:23, Radim Krčmář wrote: > 2017-08-10 15:35+0200, David Hildenbrand: >> I also have a patch that allows VMX and nVMX to use the UC (unchached) >> memory type. >> . >> However I am not sure if we have to take care of anything special in that >> case? Any insights? > > We're modifying the EPT structure through cache in root mode and I think > the cache would have to be manually flushed before entering non-root > mode. > > And UC accesses are going to be slower, so I don't see the benefits for > VMX. We can allow UC in nVMX as it will make no difference. > That would mean, even fake it's existence but always create EPTP with WB for nVMX? -- Thanks, David