From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] KVM: VMX: Translate interrupt shadow when waiting on NMI window Date: Tue, 16 Feb 2010 12:17:05 +0200 Message-ID: <20100216101705.GG2995@redhat.com> References: <4B7A625C.4070803@siemens.com> <20100216100057.GC2995@redhat.com> <4B7A6D9A.5030900@siemens.com> <20100216100635.GE2995@redhat.com> <4B7A7015.6000802@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , Marcelo Tosatti , kvm To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:23023 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932603Ab0BPKRK (ORCPT ); Tue, 16 Feb 2010 05:17:10 -0500 Content-Disposition: inline In-Reply-To: <4B7A7015.6000802@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: 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. > blocked-by-STI is set, not we. But, of course, we could also translate > STI into MOV SS blocking unconditionally. Whatever is preferred. > -- Gleb.