From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx2.redhat.com ([66.187.237.31]) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1KvS5j-0004gk-7v for kexec@lists.infradead.org; Thu, 30 Oct 2008 07:37:15 +0000 Message-ID: <490963DF.90703@redhat.com> Date: Thu, 30 Oct 2008 08:35:59 +0100 From: Chris Lalancette MIME-Version: 1.0 Subject: Re: [PATCH 0/2] kvm: disable virtualization on kdump References: <4904676F.3020706@redhat.com> <490487C1.1010707@redhat.com> <20081026213927.GF23893@blackpad> <49058645.9010005@redhat.com> <20081027122808.GH23893@blackpad> <4905C9ED.807@redhat.com> <20081028194530.GK23893@blackpad> <49082FD0.3040009@redhat.com> <4908975A.7050900@redhat.com> In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: "Eric W. Biederman" Cc: Andrew Morton , Eduardo Habkost , kvm@vger.kernel.org, kexec@lists.infradead.org, Haren Myneni , Simon Horman , Avi Kivity , Vivek Goyal Eric W. Biederman wrote: >>>> svm can writeback into memory at odd times if we don't do this, and the cost >> is >>>> small - clear a bit in EFER. There's no reason to be lazy. >>>> >>> Especially if we can clear that bit unconditionally (when >>> EFER is present) I'm all for it. >>> >> That is the case. > > Cool. I forget if we have to test for EFER on 32bit, or if we can just wrmsr > and be done with it. Regardless that sounds easy to do on the kexec path. I'm pretty sure you have to test for it first; pre-64 bit x86 hardware doesn't have the EFER register, so you'll fault on access. On the other hand pre-64 bit x86 hardware doesn't usually (ever?) have VT extensions either. -- Chris Lalancette _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Lalancette Subject: Re: [PATCH 0/2] kvm: disable virtualization on kdump Date: Thu, 30 Oct 2008 08:35:59 +0100 Message-ID: <490963DF.90703@redhat.com> References: <4904676F.3020706@redhat.com> <490487C1.1010707@redhat.com> <20081026213927.GF23893@blackpad> <49058645.9010005@redhat.com> <20081027122808.GH23893@blackpad> <4905C9ED.807@redhat.com> <20081028194530.GK23893@blackpad> <49082FD0.3040009@redhat.com> <4908975A.7050900@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Andrew Morton , Eduardo Habkost , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Haren Myneni , Simon Horman , Avi Kivity , Vivek Goyal To: "Eric W. Biederman" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kexec-bounces-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Errors-To: kexec-bounces+glkk-kexec=m.gmane.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: kvm.vger.kernel.org Eric W. Biederman wrote: >>>> svm can writeback into memory at odd times if we don't do this, and the cost >> is >>>> small - clear a bit in EFER. There's no reason to be lazy. >>>> >>> Especially if we can clear that bit unconditionally (when >>> EFER is present) I'm all for it. >>> >> That is the case. > > Cool. I forget if we have to test for EFER on 32bit, or if we can just wrmsr > and be done with it. Regardless that sounds easy to do on the kexec path. I'm pretty sure you have to test for it first; pre-64 bit x86 hardware doesn't have the EFER register, so you'll fault on access. On the other hand pre-64 bit x86 hardware doesn't usually (ever?) have VT extensions either. -- Chris Lalancette