From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH] KVM: VMX: Translate interrupt shadow when waiting on NMI window Date: Tue, 16 Feb 2010 11:27:07 +0100 Message-ID: <4B7A72FB.8020709@siemens.com> References: <4B7A625C.4070803@siemens.com> <20100216100057.GC2995@redhat.com> <4B7A6D9A.5030900@siemens.com> <20100216100635.GE2995@redhat.com> <4B7A7015.6000802@siemens.com> <20100216101705.GG2995@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Marcelo Tosatti , kvm To: Gleb Natapov Return-path: Received: from thoth.sbs.de ([192.35.17.2]:20264 "EHLO thoth.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932603Ab0BPK11 (ORCPT ); Tue, 16 Feb 2010 05:27:27 -0500 In-Reply-To: <20100216101705.GG2995@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Gleb Natapov wrote: > On Tue, Feb 16, 2010 at 11:14:45AM +0100, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Tue, Feb 16, 2010 at 11:04:10AM +0100, Jan Kiszka wrote: >>>> Gleb Natapov wrote: >>>>> On Tue, Feb 16, 2010 at 10:16:12AM +0100, Jan Kiszka wrote: >>>>>> Found while browsing Xen code: While we assume that the STI interrupt >>>>>> shadow also inplies virtual NMI blocking, some processors may have a >>>>>> different opinion (SDM 3: 22.3). To avoid misunderstandings that would >>>>>> cause endless VM entry attempts, translate STI into MOV SS blocking when >>>>>> requesting the NMI window. >>>>>> >>>>> Why not just remove "block by STI" check in vmx_nmi_allowed()? IIRC this >>>>> is documented that on some CPUs STI does not block NMI. >>>>> >>>> Probably because we will stumble and fall on those CPUs that do care. >>>> >>> But this defines behaviour of cpu _we_ emulate. So on _our_ cpu NMI will >>> not be blocked by STI. >> The host CPU decides if it accepts an NMI injections while > Are you sure? I haven't found such check during VMENTRY. I also only find the explicitly stated exclusion of MOV SS blocking vs. NMI injection. If we can rely on this, removing STI blocking from vmx_nmi_allowed should suffice. Or, better, can we get an official confirmation from Intel? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux