From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: swapping with MMU Notifiers V2 Date: Tue, 29 Jan 2008 20:05:20 +0200 Message-ID: <479F6AE0.3080702@qumranet.com> References: <20080129145021.GJ7233@v2.random> <479F50D6.4020005@de.ibm.com> <479F532C.1020503@qumranet.com> <479F55D6.1090807@de.ibm.com> <20080129175420.GR7233@v2.random> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: carsteno-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org, kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Andrea Arcangeli Return-path: In-Reply-To: <20080129175420.GR7233-lysg2Xt5kKMAvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Andrea Arcangeli wrote: > On Tue, Jan 29, 2008 at 05:35:34PM +0100, Carsten Otte wrote: > >> Avi Kivity wrote: >> >>> Every arch except s390 needs it. An ugly #ifndef >>> CONFIG_KVM_HARDWARE_TLB_SYNC is preferred to duplicating the code. >>> >> BTW, from reading AMDs spec I don't expect NPT to need this vehicle >> > > By your conclusion I suppose you thought NPT maps guest physical to > host virtual. If it was the case the cpu would to walk three layer of > pagetables (each layer is an arrow): guest virtual -> guest physical > -> host virtual -> host physical. Instead it's just guest virtual -> > guest physical -> host physical. Or even less for shadow: guest > virtual -> host physical, which is why shadow should be faster for > number crunching still (and definitely slower for dbms). > If a hypervisor mandates (host virtual) == (guest physical), it would work. x86 still misses the dual-tagged tlb, so mmu notifiers are needed regardless. With s390, they have an additional offset parameter, so (host virtual) == (guest physical) + offset, so qemu can coexist with the guest, and dual tagged tlb so that a host invalidate also evicts guest tlb entries. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/