From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH v1 2/2] KVM: VMX: always require WB memory type for EPT Date: Thu, 10 Aug 2017 22:09:33 +0200 Message-ID: <231aba07-07c9-9f3e-d61f-a270cb88cc83@redhat.com> References: <20170810133512.13442-1-david@redhat.com> <20170810133512.13442-3-david@redhat.com> <4e7e54e0-87fe-26ea-c90b-1472aa973398@redhat.com> <20170810183056.GY2547@char.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Bandan Das To: Konrad Rzeszutek Wilk , Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:40274 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752800AbdHJUJh (ORCPT ); Thu, 10 Aug 2017 16:09:37 -0400 In-Reply-To: <20170810183056.GY2547@char.us.oracle.com> Content-Language: en-US Sender: kvm-owner@vger.kernel.org List-ID: On 10.08.2017 20:30, Konrad Rzeszutek Wilk wrote: > On Thu, Aug 10, 2017 at 04:42:02PM +0200, Paolo Bonzini wrote: >> On 10/08/2017 15:35, David Hildenbrand wrote: >>> We already always set that type but don't check if it is supported. Also >>> for nVMX, we only support WB for now. Let's just require it. >>> >>> Signed-off-by: David Hildenbrand >> >> It may only happen on a broken nested hypervisor, so the patch is okay. > > Is there one in the wild? I think only the following scenario would see a change: Hypervisor supports but doesn't announce the WB memory type for EPT. KVM runs as nested hypervisor. It will now refuse to use EPT but should continue to work without EPT. In this case, the hypervisor would have a BUG and we as a nested hypervisor would do the right thing. >> >> Paolo >> -- Thanks, David