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 11:14:45 +0100 Message-ID: <4B7A7015.6000802@siemens.com> References: <4B7A625C.4070803@siemens.com> <20100216100057.GC2995@redhat.com> <4B7A6D9A.5030900@siemens.com> <20100216100635.GE2995@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 goliath.siemens.de ([192.35.17.28]:22825 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932719Ab0BPKPF (ORCPT ); Tue, 16 Feb 2010 05:15:05 -0500 In-Reply-To: <20100216100635.GE2995@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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 blocked-by-STI is set, not we. But, of course, we could also translate STI into MOV SS blocking unconditionally. Whatever is preferred. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux