From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH 0/30] nVMX: Nested VMX, v9 Date: Mon, 16 May 2011 09:38:47 +0300 Message-ID: <20110516063847.GM19019@redhat.com> References: <1304842511-nyh@il.ibm.com> <4DC7CD81.2070305@redhat.com> <20110511082027.GG19019@redhat.com> <20110512154228.GA7943@fermat.math.technion.ac.il> <20110512155727.GA20193@redhat.com> <20110512163115.GA13138@fermat.math.technion.ac.il> <20110512165157.GC20193@redhat.com> <4DCC123B.3080006@redhat.com> <20110515231140.GA17294@fermat.math.technion.ac.il> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , kvm@vger.kernel.org, abelg@il.ibm.com To: "Nadav Har'El" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:15354 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751529Ab1EPGi6 (ORCPT ); Mon, 16 May 2011 02:38:58 -0400 Content-Disposition: inline In-Reply-To: <20110515231140.GA17294@fermat.math.technion.ac.il> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, May 16, 2011 at 02:11:40AM +0300, Nadav Har'El wrote: > On Thu, May 12, 2011, Avi Kivity wrote about "Re: [PATCH 0/30] nVMX: Nested VMX, v9": > > Ah, yes. For live migration to work, all vmcb state must be accessible > > via vendor-independent accessors once an exit is completely handled. > > For example, GPRs are accessible via kvm_register_read(), and without > > nesting, interrupt state is stowed in the interrupt queue, but if you > > keep IDT_VECTORING_INFO live between exit and entry, you can lose it if > > you migrate at this point. > > Hi, I can quite easily save this state in a different place which is saved - > The easiest will just be to use vmcs12, which has place for exactly the fields > we want to save (and they are rewritten anyway when we exit to L1). > This will not address the problem that the state will not be visible to generic logic in x86.c. > Avi, would you you like me use this sort of solution to avoid the extra > state? Of course, considering that anyway, live migration with nested VMX > probably still doesn't work for a dozen other reasons :( > > Or do you consider this not enough, and rather that it is necessary that > nested VMX should use exactly the same logic as nested SVM does - namely, > use tricks like SVM's "exit_required" instead of our different tricks? > Given two solutions I prefer SVM one. Yes, I know that you asked Avi :) -- Gleb.