From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC PATCH 0/3] generic hypercall support Date: Fri, 08 May 2009 14:37:18 +0300 Message-ID: <4A04196E.7090908@redhat.com> References: <4A0049CD.3080003@gmail.com> <20090505231718.GT3036@sequoia.sous-sol.org> <4A010927.6020207@novell.com> <20090506072212.GV3036@sequoia.sous-sol.org> <4A018DF2.6010301@novell.com> <20090506160712.GW3036@sequoia.sous-sol.org> <4A031471.7000406@novell.com> <20090507233503.GA9103@amt.cnet> <20090507234311.GA9517@amt.cnet> <4A03E579.8030201@redhat.com> <20090508103253.GC3011@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gregory Haskins , Chris Wright , Gregory Haskins , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Anthony Liguori To: Marcelo Tosatti Return-path: Received: from mx2.redhat.com ([66.187.237.31]:46576 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752821AbZEHLiv (ORCPT ); Fri, 8 May 2009 07:38:51 -0400 In-Reply-To: <20090508103253.GC3011@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: Marcelo Tosatti wrote: >>> Also it would be interesting to see the MMIO comparison with EPT/NPT, >>> it probably sucks much less than what you're seeing. >>> >>> >> Why would NPT improve mmio? If anything, it would be worse, since the >> processor has to do the nested walk. >> > > I suppose the hardware is much more efficient than walk_addr? There's > all this kmalloc, spinlock, etc overhead in the fault path. > mmio still has to do a walk_addr, even with npt. We don't take the mmu lock during walk_addr. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.